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Platzer-Björkman, Charlotte. "Band Alignment Between ZnO-Based and Cu(In,Ga)Se2 Thin Films for High Efficiency Solar Cells." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6263.
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Thin-film solar cells based on Cu(In,Ga)Se2 contain a thin buffer layer of CdS in their standard configuration. In order to avoid cadmium in the device for environmental reasons, Cd-free alternatives are investigated. In this thesis, ZnO-based films, containing Mg or S, grown by atomic layer deposition (ALD), are shown to be viable alternatives to CdS. The CdS is an n-type semiconductor, which together with the n-type ZnO top-contact layers form the pn-junction with the p-type Cu(In,Ga)Se2. From device modeling it is known that a buffer layer conduction band (CB) position of 0-0.4 eV above that of the Cu(In,Ga)Se2 layer is consistent with high photovoltaic performance. For the Cu(In,Ga)Se2/ZnO interface this position is measured by photoelectron spectroscopy and optical methods to –0.2 eV, resulting in increased interface recombination. By including sulfur into ZnO, a favorable CB position to Cu(In,Ga)Se2 can be obtained for appropriate sulfur contents, and device efficiencies of up to 16.4% are demonstrated in this work. From theoretical calculations and photoelectron spectroscopy measurements, the shift in the valence and conduction bands of Zn(O,S) are shown to be non-linear with respect to the sulfur content, resulting in a large band gap bowing. ALD is a suitable technique for buffer layer deposition since conformal coverage can be obtained even for very thin films and at low deposition temperatures. However, deposition of Zn(O,S) is shown to deviate from an ideal ALD process with much larger sulfur content in the films than expected from the precursor pulsing ratios and with a clear increase of sulfur towards the Cu(In,Ga)Se2 layer. For (Zn,Mg)O, single-phase ZnO-type films are obtained for Mg/(Zn+Mg) < 0.2. In this region, the band gap increases almost linearly with the Mg content resulting in an improved CB alignment at the heterojunction interface with Cu(In,Ga)Se2 and high device efficiencies of up to 14.1%.
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Hildebrandt, Thibaud. "Optimisation des interfaces absorbeur/couche tampon/fenêtre avant dans les cellules solaires à base de Cu(In,Ga)Se2." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066720.
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Le remplacement du CdS dans les cellules solaires à base de Cu(In,Ga)Se2 est un des défis majeurs de la communauté. À ce jour un des matériaux les plus prometteurs est le Zn(S,O,OH) déposée par voie chimique en solution. En raison de la faible vitesse de dépôt du matériau et des phénomènes de métastabilités présents dans les dispositifs formés, il apparaît nécessaire d’optimiser les conditions expérimentales et les interfaces. La 1ère partie de ces travaux a été consacré à l’optimisation des conditions de dépôt des couches minces de Zn(S,O,OH) grâce à l’introduction d’additifs. Il a été possible de souligner l’effet des additifs sur la composition des couches déposées et sur les vitesses de réaction. La 2ème partie de ces travaux a été consacrée à l’optimisation des conditions de dépôt par pulvérisation cathodique de la fenêtre avant (Zn,Mg)O/ZnO :Al permettant une diminution des phénomènes de métastabilité et une limitation de la migration de sodium jusqu’au Zn(S,O,OH). Ces conditions combinées à une variation de la composition de la surface du CIGSe a permis d’obtenir des rendements de photo-conversion supérieurs à ceux des références à base de CdSThe replacement of CdS-based buffer layer in Cu(In,Ga)Se2 solar cells has been one of the main challenges of the research community for the last decade. Today, one of the most promising alternative material is the chemically bath deposited Zn(S,O,OH). Because of its low deposition rate and of metastable behavior, it becomes necessary to proceed to an optimization of experimental conditions and of the various interfaces. The first part of this work has been dedicated to the optimization of the deposition bath thanks to the introduction of new additives. It has been possible to underline the additive effects on both the deposition rate and on the chemical composition of the deposited layers. The second part of this work has been dedicated to the optimization of the (Zn,Mg)O/ZnO:Al window layer. Thanks to an improvement of the sputtering conditions, it has been possible to reduce metastability of the solar cells, and to limit sodium migration up to the Zn(S,O,OH) layer. These optimized conditions combined to the variation of the CIGSe surface composition have allowed us to outperform CdS-based references solar cells
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Lox, Josephine F. L., Zhiya Dang, Anh Mai Lê, Eileen Hollinger, and Vladimir Lesnyak. "Colloidal Cu–Zn–In–S-Based Disk-Shaped Nanocookies." American Chemical Association, 2019. https://tud.qucosa.de/id/qucosa%3A74324.
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We present a colloidal synthesis of quaternary Cu–Zn–In–S (CZIS) nanoplatelets (NPLs) by means of partial cation exchange. Starting with the synthesis of highly monodisperse binary CuS NPLs with lateral dimensions of ∼64 nm and thickness of ∼5 nm, we further performed a cation exchange reaction in which copper was partly replaced by indium, leading to Cu–In–S NPLs. To enhance the stability of the resulting NPLs and to improve their optical properties, we carried out the ZnS shell growth via both the heterogeneous nucleation of ZnS on the NPLs and via partial cation exchange on the surface of the particles. The latter reaction resulted, however, in rather an alloyed than the core/shell structure, whereas the reaction between zinc and sulfur precursors yielded unusual cookie-like hexagonal shaped structure, in which ZnS trigonal extensions grew only on one of the basal planes of the plates along the thickness direction. Upon ZnS growth, the lateral dimensions of the resulting core/shell CZIS/ZnS and alloyed CZIS NPLs distinctly increased to ∼80 and ∼75 nm, respectively. The analysis of the optical properties of the alloyed CZIS NPLs showed photoluminescence (PL) in the range from 780 to 820 nm depending on the reaction time and temperature. This PL signal originated mainly from small nanoparticles formed as a byproduct in the synthesis. In contrast to the alloyed NPLs, PL measurements of the core/shell CZIS/ZnS platelets showed a weak emission in the near-infrared region (PL maximum at approx. 1110 nm), which so far has rarely been reported for the copper chalcogenide-based two-dimensional structures.
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Howard, P. "Precipitation and creep in an Al-Zn-Mg-Cu based alloy." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356709.
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Guo, Yanzhi. "Synthesis, characterization and catalytic application of Ru/Sn-and Cu/Zn-based nanocomposites." [S.l.] : [s.n.], 2006. http://deposit.d-nb.de/cgi-bin/dokserv?idn=98188833X.
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Hreid, Tubshin. "Co-electrodeposition of Cu-Zn-Sn film and synthesis of Cu2ZnSnS4 photovoltaic material." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/94160/12/Tubshin%20Hreid%20Thesis.pdf.
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This work contributes to electrochemical fabrication of Cu-Zn-Sn alloy thin film and synthesis of kesterite Cu2ZnSnS4 film which is a promising new material for sustainable photovoltaic devices. Co-electrodeposition provides a low-cost, time-saving and environmentally friendly approach to fabricate Cu-Zn-Sn film and has a potential application in large scale and high throughput production of Cu2ZnSnS4 material. This work includes identification of critical parameters controlling the formation of homogeneous Cu-Zn-Sn film, investigation of its growth mechanism, precisely controlled synthesis of kesterite Cu2ZnSnS4 film and effects of metal ions concentration on formation of Cu-Zn-Sn film and its application in kesterite Cu2ZnSnS4 solar cells.
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Kühl, Stefanie Verfasser], and Robert [Akademischer Betreuer] [Schlögl. "Synthesis and Characterization of Cu-based Catalysts resulting from Cu,Zn,XHydrotalcite-like Compounds / Stefanie Kühl. Betreuer: Robert Schlögl." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2012. http://d-nb.info/1021219762/34.
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Hutchings, K. D. "High throughput combinatorial screening of Cu-Zn-Sn-S thin film libraries for the application of Cu2ZnSnS4 photovoltaic cells." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/8771.
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The naturally occurring mineral of Cu2ZnSnS4 (CZTS) is a promising alternative absorber layer for thin film based photovoltaic devices. It has the remarkable advantage that it consists of abundant, inexpensive and non-toxic elements compared to its crystallographically related and highly successful counterparts: the Cu(In,Ga)(S,Se)2 (CIGSSe) and CuIn(S, Se)2 (CISSe) material systems. Therefore, there is real commercial potential for reduced material costs and improved device efficiencies. A two-stage high throughput combinatorial process for the fabrication of Cu-Zn-Sn-S thin film libraries is presented, which consists of either sequentially stacking or co-depositing Cu,Sn and Zn precursor layers by DC magnetron sputtering followed by a sulphurisation process. Sputtering conditions and target-substrate geometry are developed to give compositionally graded Cu-Zn-Sn precursor layers spanning a wide spatial region around the point of stoichiometry. Conversion into Cu-Zn-Sn-S libraries is achieved by thermally evaporating a uniform layer of sulphur directly onto the metal alloy and annealing the sample at 500 °C in a furnace. Effects of the precursor composition on the structural properties of the films prior to the incorporation of sulphur are investigated. The sulphurised libraries are then studied by Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy as a function of composition, to assess the effects on morphology and phase formation. Observations of changes in lattice parameters and crystallinity are clear. The opto-electronic and electrical properties of the CZTS film libraries are measured using photoconductivity and hot point probe techniques, respectively. Changes in the band gap and conductivity type are studied as a function of atomic ratios. Based on high performing compositions, devices have been fabricated with the highest achieving cell at 1.26 %. The observations are discussed in the context of the particular compositions and synthesis conditions, and recommendations are made for further work.
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Hultqvist, Adam. "Cadmium Free Buffer Layers and the Influence of their Material Properties on the Performance of Cu(In,Ga)Se2 Solar Cells." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-133112.
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CdS is conventionally used as a buffer layer in Cu(In,Ga)Se2, CIGS, solar cells. The aim of this thesis is to substitute CdS with cadmium-free, more transparent and environmentally benign alternative buffer layers and to analyze how the material properties of alternative layers affect the solar cell performance. The alternative buffer layers have been deposited using Atomic Layer Deposition, ALD. A theoretical explanation for the success of CdS is that its conduction band, Ec, forms a small positive offset with that of CIGS. In one of the studies in this thesis the theory is tested experimentally by changing both the Ec position of the CIGS and of Zn(O,S) buffer layers through changing their gallium and sulfur contents respectively. Surprisingly, the top performing solar cells for all gallium contents have Zn(O,S) buffer layers with the same sulfur content and properties in spite of predicted unfavorable Ec offsets. An explanation is proposed based on observed non-homogenous composition in the buffer layer. This thesis also shows that the solar cell performance is strongly related to the resistivity of alternative buffer layers made of (Zn,Mg)O. A tentative explanation is that a high resistivity reduces the influence of shunt paths at the buffer layer/absorber interface. For devices in operation however, it seems beneficial to induce persistent photoconductivity, by light soaking, which can reduce the effective Ec barrier at the interface and thereby improve the fill factor of the solar cells. Zn-Sn-O is introduced as a new buffer layer in this thesis. The initial studies show that solar cells with Zn-Sn-O buffer layers have comparable performance to the CdS reference devices. While an intrinsic ZnO layer is required for a high reproducibility and performance of solar cells with CdS buffer layers it is shown in this thesis that it can be thinned if Zn(O,S) or omitted if (Zn,Mg)O buffer layers are used instead. As a result, a top conversion efficiency of 18.1 % was achieved with an (Zn,Mg)O buffer layer, a record for a cadmium and sulfur free CIGS solar cell.Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 717
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Sun, Jiqing. "Graphene-based nanomaterials as electrodes for fuel cells and Zn-air batteries." Thesis, Griffith University, 2018. http://hdl.handle.net/10072/380070.
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In pursuit of solving the foreseeable depletion of fossil energies and environmental pollution caused by combustion of them, great efforts have been devoted to exploring renewable and clean energies, like the solar energy, nuclear energy, and geothermal energy, etc. as well as the technologies in converting these new energies into the form of usable electricity. In this regard, (rechargeable) zinc-air batteries and fuel cells have demonstrated promising potentials due to their large output energy density, power density and more importantly, their environmental compatibility. To consume oxygen molecules at cathode, these devices suffer greatly from the large overpotential and sluggish kinetics from the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Platinum, iridium and other noble metal-based electrocatalysts (NMCs) are conventionally used at the cathode of zinc-air batteries and fuel cells. However, the NMCs are subjected to high cost and insufficient durability. Thus, substituting the NMCs with other earth-abundant elements is currently imperative for the large-scale commercialization of the zinc-air batteries and fuel cells.
Within this framework, this thesis attempts to utilize graphene as the building blocks to couple with other active elements, e.g. transition metal ions and nitrogen doped disordered carbon to fabricate advanced electrocatalysts for OER and ORR. A series of synthesizing methods have been developed to synthesize the graphene-based nanocomposites, including room-temperature coordination adsorption, hydrothermal treatment, and high-temperature calcination, etc. The physical features of the resultant nanocomposites have been thoroughly investigated by using XRD, SEM, and TEM. Meanwhile, their electrochemical performances were explored in terms of the potential-current response and the corresponding working durability. Besides, the associated origin of their intrinsic activity has been investigated and discussed.
Molecular Ni–/Co–porphyrin multilayers were spontaneously adsorbed on the surface of graphene sheets layer-by-layer via non-covalent forces such as Van der Waals’ force and π-π interactions. It was observed that the electrochemical performance of the nanocomposite could be tuned by controlling the number of the Ni–/Co–porphyrin layers on the surface of graphene. This is ascribed to the counterbalance between the steric hindrance and the content of the active species. Such research work manifested the controllability of the OER/ORR performance at the molecular level and revealed the essential influence between the content of the active sites and the steric hindrance caused by their spatial accommodation.
To implement a low-cost and scalable synthesis strategy, carbon black NPs and amorphous CoBi nanoplates were assembled with graphene to build a sandwich-like nanocomposite by use of amphipathicity of graphene oxide. The obtained sandwich-like nanocomposite exhibited excellent ORR/OER performance, which was comparable to the state-of-the-art materials. The performance enhancement towards ORR was assigned to the enlarged accessible active surface area of the nanocomposite catalyst. Without changing the chemical composition of the active species, this work highlighted the significance of the rational design of the geometrical configuration by means of the non-covalent force in an electrocatalyst. The resultant nanocomposite was further assembled in a rechargeable zinc-air battery to demonstrate its practicability.
The lack of the high-efficiency and noble metal-free electrocatalyst in the acid media has been an intractable problem for years. To address this issue, a disordered carbon layer impregnated with Co-N on the surface of graphene sheet was fabricated by pyrolysing the hydrothermal product of graphene oxide and cobalt gluconate. The resultant nanocomposite exhibited remarkable activity to ORR in both alkaline and acid media, which was due to the high dispersion of abundant active sites. Moreover, different active working sites in alkaline and acid condition for the obtained material were suggested. This inspired us to investigate different roles of the metal species in the ORR electrocatalysts.
For the nitrogen-doped carbon materials, the pyridinic nitrogen doping is believed to possess the highest activity for ORR in alkaline environment. To verify that theory and further enhance the activity of the nitrogen-doped carbon materials, an ultrathin holey carbon layer coupled with graphene nanosheets was prepared. The edge enriched feature makes it easier to form pyridinic nitrogen during the nitrogen doping process. The obtained composite displayed the expected outstanding ORR performance in alkaline media and even surprisingly high activity in acid solution. The rationality of the design of this material was manifested by solving the commonly encountered insufficient charge transfer ability and stability of the holey graphene materials while preserving the high activity in the holey carbon sites.
In a nutshell, this thesis contributes to the exploration of the graphene-based OER/ORR electrocatalyst in the aspects of i) tuning the electrochemical activity of the transition metal based electrocatalyst at the molecular level; ii) isolating and highlighting the significance in geometrical configuration of the ORR electrocatalyst with respect to kinetic process; iii) suggesting and verifying the different active sites of the same electrocatalyst tested under different pH values; iv) selectively inducing the formation of the active pyridinic nitrogen species in the ultrathin holey carbon layer coupled on the surface of graphene nanosheet.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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Fagieh, Taghreed M. "ICP-MS determination of Zn, Cu, Fe and Mn in muscle cells as potential markers of oxidative stress." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/27011.
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Oxidative stress is imbalance between oxidant and antioxidant levels in living systems. Human cells are protected from reactive oxygen species by endogenous enzymatic antioxidants. Most of these compounds require particular redox metals in their structures as cofactors to allow them to scavenge the free radicals such as Cu, Zn-SOD, Mn-SOD and catalase (Fe). The aim of this study was to quantify these metals in human cells to evaluate their effectiveness as novel biomarkers for measuring oxidative stress. The metals (Zn, Cu, Fe, Mn) were measured in vitro in skeletal muscle cells (C2C12) which were incubated under hypoxia/hyperoxia conditions generated by varying oxygen level from 1%-60% for 24 and 48 hours. Two methods were used to perform the analysis. ICP-MS was applied to liquid samples to quantify Zn, Cu, Fe and Mn in cell populations. And LA-ICP-MS was employed to solid samples to measure their intensity in individual cells. The data acquired from both techniques are positively correlated confirming the reliability of the two approaches. All elements of interest were successfully measured except Mn which was not detected in single cells using LA-ICP-MS due to the limit of detection. Interestingly, the results showed that their concentration increased dramatically in cells grown at 25%-60% O2, the most significant increase was in Cu at 60%O2. None showed any increase at 5%-15% O2 indicating normoxia states. At 1%O2, all elements except Fe showed a significant increase and the most remarkable growth was in Mn. More interestingly, increasing incubation to 48 hours for liquid samples had differing effects on the elements. Zn and Cu concentrations were unaffected by increasing incubation time except at 60%O2 where they showed further growth. In contrast, Mn concentration grew sharply over oxygen levels of 30%-50% with no further effect at 1%, while Fe concentration decreased at 1%O2 and grew steadily over oxygen levels of 5%-60%. It can be concluded that all four elements were significantly affected by stress conditions applied to cells, but at different rates. Importantly, a novel analytical method was introduced in this current study since there have been no previous reported investigations measuring changes in concentration of redox-active elements in human cells subjected to different controlled oxidative stress conditions in vitro.
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Kämäräinen, A. (Anne). "GIS-based spatial assessment of Au, Ni and Cu-Zn exploration conducted in Central Finnish Lapland." Master's thesis, University of Oulu, 2017. http://urn.fi/URN:NBN:fi:oulu-201705181953.
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The objective of this Master’s project was to produce a statistical dataset on orogenic gold, magmatic nickel-copper sulfide and volcanogenic massive sulfide copper-zinc exploration performed in Finnish Central Lapland over the past 20 years and to produce a time series of areas covered by Au, Ni, Cu and Zn exploration tenements. Secondly, the aim was also to give an overview on the mining history and to create a raster intensity map of already found ore in the study area and to spatially compare this to pre-existing mineral potential maps. The study area in question is defined by the GovAda project and a considerable part of its bedrock is composed of volcanic and sedimentary rocks belonging to the Central Lapland greenstone belt. This work is mainly based on a database of exploration tenements of Finland obtained from the Finnish Safety and Chemical Agency, the Fennoscandian Ore Deposit Database, and information on historic and current mine areas and their production. The preliminary data manipulation was primarily conducted using ArcGIS in conjunction with MS Excel, and resulted in total of 1938 claims to work with.
The results show that the exploration ‘boom’ in the study area has been ongoing since 2003 and that the metal prices and the amount of investment can be used as a reliable predictor of change in areas of active exploration tenements mainly for orogenic gold. In the case of magmatic Ni-Cu, the independent variables are more unstable and therefore are not as reliable. For the VMS type, it was impossible to produce a time series and calculate correlations due to the fact that there have only been 3 exploration tenements granted towards VMS exploration during the time period of interest. Based on spatial comparison of the raster intensity maps, locations of exploration tenements and mineral potential maps, the already known deposits are all located mainly in areas of high mineral potential and it would seem that most of mineral exploration has been also carried out in these high prospectivity areas.
Out of the 19 known deposits in the study area, only two have been discovered since 1995. There are two mines currently in operation and mining volumes have been rising every year since 2012 and are expected to rise even more in the future. Also, the future for mineral exploration looks brighter as the investments and drilling activities have recently shown signs of recovery.
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Santos, Nathália Villa dos. "Efeitos da expressão da Cu, Zn-SOD em cultura primária de células da medula espinhal." reponame:Repositório Institucional da UFABC, 2014.
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Orientadora: Profa. Dra. Giselle CerchiaroDissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Biossistemas, 2015.
A proteina Cu,Zn Superoxido Dismutase, uma metalo proteina que atua na dismutacao do ion superoxido em agua e peroxido de hidrogenio, esta presente em todas as celulas do organismo e tambem esta relacionada com doencas neurodegenerativas como Esclerose Lateral Amiotrofica Familia, que acomete neuronios motor. Buscamos contribuir para a elucidacao do papel bioquimico e fisiologico da proteina Cu,Zn-SOD em cultura primaria de celulas da medula espinhal obtidas de neonatos (0-2 dias) de ratos da linhagem Wistar. Para isso, foi avaliado in vitro o papel do estresse oxidativo induzido por 100 ¿ÊM de H2O2 nos tempos de 3 e 6 horas. Os resultados mostraram que celulas de cultura primaria de medula espinhal, quando expostas a estresse oxidativo, levam a ativacao de caspases, portanto encontra-se populacoes em apoptose precoce e tardia, em ambos tempos, comparado ao controle negativo. Tambem foi observado a relocalizacao da proteina SOD1 nas condicoes de estresse oxidativo e controle, estando mais expressa na porcao nuclear e com atividade dismutasica integra. Na porcao citoplasmatica, ha a presenca de Cu,Zn-SOD, no entanto nao mostra atividade.
The protein Cu,Zn-Superoxide Dismutase is a metaloprotein that convert superoxide radicals to molecular oxygen and hydrogen peroxide. This protein is present in all cells of the body and also is related to neurodegenerative diseases as ALS, which affects motor neurons. The objective of this study was contribute to the elucidation of the biochemical and physiological role of the protein Cu,Zn-SOD in primary cultures of spinal cord cells from newborns (0-2 days) of Wistar rats. So we evaluated in vitro the role of oxidative stress induced by 100uM of H2O2 in 3 and 6 hours. The results showed that these cells when exposed to oxidative stress leading to caspase activation in early and late apoptosis in both times, as compared to the negative control. It was also observed relocation of SOD1 protein in conditions of oxidative stress and control, being more expressed in the nuclear portion with integrates activity. However, the cytoplasmic portion of Cu, Zn-SOD was not activated.
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Fairbrother, Andrew. "Development of Cu(2)ZnSn(S,Se)(4) based solar cells." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/145615.
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Thin film solar cell technologies are rapidly developing, and chalcopyrite (Cu(In,Ga)Se2) based devices have demonstrated the highest power conversion efficiencies on the laboratory scale. However, in spite of this promise, there are concerns about the mid- to long-term viability of the material because it contains the relatively scarce elements of indium and gallium. This has led to the development of kesterite (Cu2ZnSn(S,Se)4) based photovoltaic technologies, which is particularly promising because of its similarities with the chalcopyrite material. In this material system indium and gallium are replaced by the more earth abundant elements of zinc and tin. Device efficiencies are still lower than Cu(In,Ga)Se2, but further research and development has led to significant increases in performance in the past few years. To date the device structure and processing parameters for kesterite based devices has been mostly copied from chalcopyrite based technologies.
The objective of this thesis is to further develop these kesterite based technologies, and it covers some of the basic challenges related to it, including secondary phase formation and identification, and optimization of the front and back contact areas. Particular emphasis is placed on the deposition and thermal processing of this compound, and how these affect secondary phase formation and device properties. It is based on several articles which explore these in depth. This includes detailed characterization by Raman scattering spectroscopy, x-ray diffraction, scanning electron microscopy, and other techniques. Highlights of the thesis work include: development of a selective chemical etch to remove ZnS, a common secondary phase in this system, which leads to significant improvements in device performance; elaboration of a sulfo-selenization method to form Cu2ZnSn(S,Se)4 from metallic precursors; and understanding the influence of thermal processing parameters on phase formation and distributionEn los últimos años ha habido un rápido desarrollo en las tecnologías de celdas solares basadas en capa delgada, siendo hasta el momento los dispositivos basados en calcopiritas (Cu(In,Ga)Se2) los que han mostrado una mayor eficiencia de conversión fotovoltaica a escala de laboratorio. Sin embargo, y a pesar de tan prometedores resultados, existe una preocupación sobre la viabilidad a medio y largo término de estos materiales debido a la presencia en su composición de elementos relativamente escasos en la corteza terrestre, como son el In y el Ga. Esto ha llevado al desarrollo de tecnologías fotovoltaicas basadas en kesterita (Cu2ZnSn(S,Se)4), que es especialmente prometedora dada su gran similitud con la calcopirita. En este compuesto, el indio y el galio son reemplazados por elementos más abundantes como son el cinc y el estaño. Los valores de eficiencia de los dispositivos aún están por debajo de los del Cu(In,Ga)Se2, pero nuevas investigaciones y técnicas de desarrollo han llevado a importantes avances en los últimos años. A día de hoy, tanto los parámetros de fabricación como la estructura de los dispositivos basados en kesterita han seguido un camino prácticamente idéntico al de las tecnologías basadas en calcopiritas. El objetivo de esta tesis es el de profundizar en el desarrollo de las tecnologías basadas en kesterita, lo que cubre algunos de los retos básicos relacionados con ellas, como son la formación e identificación de fases secundarias o la optimización de las áreas de contacto frontal y posterior. Se ha puesto especial énfasis en la deposición y los procesos térmicos implicados en el crecimiento de este compuesto, y en ver cómo afectan a la posible formación de las fases secundarias y las propiedades del dispositivo. La tesis en sí está estructurada a partir de los diversos estudios publicados en revistas científicas. Dichos estudios incluyen una caracterización detallada por espectroscopia de dispersión Raman, difracción de rayos X, microscopia electrónica de barrido, y otras técnicas. Los puntos principales de este trabajo son: el desarrollo de un ataque químico selectivo para la eliminación del ZnS (una fase secundaria comúnmente presente en este sistema), con la consecuente mejora de las características del dispositivo; la elaboración de un método de sulfo-selenización para la formación de Cu2ZnSn(S,Se)4 a partir de precursores metálicos; y la resolución de cómo influyen los parámetros de los diferentes procesos térmicos en la formación y distribución de las fases.
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Schumann, Julia [Verfasser], Robert [Akademischer Betreuer] Schlögl, Reinhard [Akademischer Betreuer] Schomäcker, and Malte [Akademischer Betreuer] Behrens. "Cu, Zn-based catalysts for methanol synthesis / Julia Schumann. Gutachter: Reinhard Schomäcker ; Robert Schlögl ; Malte Behrens. Betreuer: Robert Schlögl." Berlin : Technische Universität Berlin, 2015. http://d-nb.info/1069578398/34.
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Gouillart, Louis. "Development of ultrathin Cu(In,Ga)Se ₂ –based solar cells with reflective back contacts." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS007.
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Réduire l’épaisseur de l’absorbeur des dispositifs photovoltaïques à base de couches minces est une voie prometteuse pour améliorer leur compétitivité industrielle, via une économie de matières premières et une cadence de production plus élevée. Cela peut aussi accroître leur efficacité en diminuant le parcours des porteurs de charge photogénérés. Cependant, l’efficacité des cellules solaires à base de Cu(In,Ga)Se ₂ (CIGS) ultramince avec une épaisseur d’absorbeur d’environ 500 nm, soit environ 5 fois inférieure aux cellules conventionnelles, est limitée par deux phénomènes : les recombinaisons non-radiatives de charges au contact arrière et l’absorption incomplète de la lumière solaire incidente. Différentes stratégies ont été étudiées afin de limiter ces pertes. Dans un premier temps, la composition des couches ultraminces de CIGS a été optimisée pour y créer un gradient du minimum de la bande de conduction. Le champ électrique résultant permet de faciliter la séparation des charges et de limiter les recombinaisons au contact arrière. L’incorporation d’argent dans la composition du CIGS a également amélioré significativement les performances des cellules ultraminces, pour aboutir à une efficacité de 14.9% (avec 540 nm d’ACIGS, sans couche antireflet), proche du record actuel de 15.2% (avec couche antireflet et 490 nm de CIGS). En parallèle, l’ajout d’une couche de passivation en alumine à l’interface entre le CIGS (470 nm) et le Mo a été étudiée, et a conduit à une augmentation de la tension de circuit ouvert de 55 mV. Dans un deuxième temps, une nouvelle architecture de contact arrière réfléchissant a été développée. Elle consiste en un miroir d’argent encapsulé dans des couches d’oxydes transparents conducteurs. A l’aide d’observations au microscope électronique en transmission, il a été montré que ce contact arrière est compatible avec la co-évaporation de CIGS à des températures ≥500°C. Grâce à une haute réflectivité et un contact ohmique avec le CIGS, il a mené à une amélioration de l’efficacité de 12.5% à 13.5% et du courant de court-circuit de 26.2 mA/cm² à 28.9 mA/cm² par rapport à un contact arrière standard en molybdène. Cette nouvelle architecture ouvre la voie à une augmentation du rendement photovoltaïque des cellules solaires CIGS ultraminces ainsi qu’à de nouvelles stratégies de piégeage optiqueReducing the absorber thickness of thin-film photovoltaic devices is a promising way to improve their industrial competitiveness, thanks to a lower material usage and an increased throughput. It can also increase their efficiency due to a shorter pathway for the separation of photogenerated charge carriers. Still, the efficiency of ultrathin Cu(In,Ga)Se ₂ -based (CIGS) solar cells , which have an absorber thickness ≤500 nm that is approximately 5 times thinner than standard devices, is limited by two phenomena: the non-radiative recombination of charge carriers at the back contact and the incomplete absorption of the incident light. Several strategies were studied in order to mitigate those losses. First, the composition of ultrathin CIGS layers was optimized to create a grading of the semiconductor’s conduction band minimum. The resulting electric field contributes to a better charge carrier separation and a lower back contact recombination rate. The incorporation of silver in the CIGS composition greatly improved the performances of ultrathin cells, leading to an efficiency of 14.9% (540 nm of ACIGS, without antireflection coating), close to the current record of 15.2% (490 nm of CIGS, with antireflection coating). Besides, the addition of an alumina passivation layer at the interface between CIGS (470 nm) and Mo was also investigated, and resulted in an improvement of the open-circuit voltage of 55 mV. Second, a novel architecture of reflective back contacts was developed. It consists of a silver mirror that is encapsulated with layers of transparent conductive oxides. Based on a transmission electron microscopy study, this back contact was shown to be compatible with the co-evaporation of CIGS at 500°C or more. Thanks to a high reflectivity and an ohmic contact with CIGS, it led to an increase of the efficiency from 12.5% to 13.5% and of the short-circuit current from 26.2 mA/cm² to 28.9 mA/cm² as compared to cells with a standard molybdenum back contact. This reflective back contact paves the way toward higher photovoltaic efficiencies as well as novel strategies for further light trapping
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Khanal, Rajendra R. "Carbon Single Wall Nanotubes: Low Barrier, Cu- Free Back Contact to CdTe Based Solar Cells." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1396625969.
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Paire, Myriam. "Highly efficient solar cells in low dimensionality based on Cu(In,Ga)Se2 chalcopyrite materials." Paris 6, 2012. http://www.theses.fr/2012PA066439.
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Dans cette thèse nous évaluons le potentiel de cellules solaires micrométriques pour une utilisation sous flux concentré. Le but de l’étude est de mettre au point une technologie photovoltaïque à haut rendement, basée sur des technologies de grandes surfaces pour obtenir de fortes productivités, qui soit en même temps économe en matières premières pour respecter les contraintes imposées par un développement du photovoltaïque à l’échelle du terawatt. La miniaturisation des cellules solaires permet d’obtenir une architecture peu résistive, qui évacue efficacement la chaleur. Les microcellules sont donc adaptées à la concentration lumineuse. Des prototypes sont fabriqués, grâce à des techniques de photolithographie. Leur test permet d’évaluer leur rendement. Un gain absolu de 5% de rendement a été mesuré; un rendement maximum de 21. 3% sur une cellule de 50 µm de diamètre à une concentration de ×475 est atteint. Les caractéristiques du régime de forte illumination sont étudiées pour la première fois sur Cu(In,Ga)Se2. La photoconductivité de cet absorbeur est examinée. L’écrantage du champ électrique de l’hétérojonction Cu(In,Ga)Se2 sous fort flux est simulé numériquement et semble expliquer l’influence de l’intensité lumineuse sur la collecte des porteurs, mise en évidence expérimentalement. La possibilité d’une application industrielle est envisagée grâce à la fabrication de microcellules à absorbeur localisé, qui a permis de déterminer une faible vitesse de recombinaison sur les surfaces latérales des cellules (< 4 103 cm/s). Une technique de dépôt sélective, l’électrodépôt, a permis la synthèse de CuInSe2 sur des microélectrodesIn this thesis we explored the potential of thin film microscale concentrator solar cells. The aim of the study is to develop a highly efficient photovoltaic technology, based on large-area processes for high throughput, and which is raw-material thrifty to meet the constraints of terawatt development. The miniaturization of thin film solar cells leads to a low resistive architecture, with easy thermal management, which is therefore adapted to the concentrating regime. The scale effects are studied from an analytical and numerical point of view. Prototype Cu(In,Ga)Se2 solar cells are fabricated with help of photolithography techniques and tested to evaluate the performance of the microcells. A 5% absolute efficiency increase was measured, which led to a 21. 3% efficiency of a 50 µm diameter microcell at a concentration of ×475. The influence of the incident spectra is highlighted. The specific features of the high illumination regime are studied for the first time on Cu(In,Ga)Se2. The photoconductive behavior of Cu(In,Ga)Se2 is analyzed. The screening of the electric field in the Cu(In,Ga)Se2 heterojunction under high light fluxes is evidenced by simulation and may explain the influence of the illumination level on the collection efficiency observed experimentally. The possibility of an industrial application is tackled via the fabrication of mesa delineated microcells, which proves that the edge surface of the microcells have a low recombination velocity (< 4 103 cm/s). A bottom-up approach is studied via electrodeposition. This selective deposition technique enables the synthesis of CuInSe2 on microelectrodes
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Mollica, Fabien. "Optimization of ultra-thin Cu(In,Ga)Se2 based solar cells with alternative back-contacts." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066556/document.
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En quelques années, l'efficacité des cellules solaires à base de Cu(In,Ga)Se2 (CIGS) est passée de 20% à 22.6%. La rapidité de ce développement montre que le CIGS est un matériaux idéal pour les technologies solaires en couches minces. Pourtant, le coût de production cette technologie doit encore être abaissé pour une meilleure compétitivité. La fabrication d'un module avec une couche CIGS plus fine permettrait d'augmenter la production d'une usine et de réduire sa consommation en métaux. Ce travail de thèse vise à réduire l'épaisseur du CIGS d'un standard de 2.0-2.5 µm à une épaisseur inférieure à 500 nm sans altérer les performances des cellules. Cependant, comme rapporté dans la littérature, nous avons observé une diminution des rendements, ce que nous avons analysé en détail en comparant simulations et caractérisations d'échantillons. Celle-ci est causée à la fois par une faible absorption de la lumière dans la couche de CIGS et par un impact important du contact arrière (fortes recombinaisons et faible réflectivité). Pour dépasser ces limites, nous démontrons à la fois théoriquement et expérimentalement que le contact arrière en molybdène peut être remplacé par un oxyde transparent conducteur couplé à un miroir métallique. Nous obtenons de cette manière de meilleurs rendements de cellules. Pour atteindre ce résultat, une optimisation du dépôt de CIGS a été nécessaire. De plus, nous prouvons qu'une couche d'oxyde perforée, insérée entre le CIGS et le contact arrière, limite les recombinaisons des porteurs de charges et réduit l'influence des courants parallèles. Au final, nous avons fabriqué une cellule avec un rendement de 10.7% sur SnO2:F passivé par Al2O3In the past three years, record efficiency of Cu(In,Ga)Se2 (CIGS) based solar cells has improved from 20% up to 22.6%. These results show that CIGS absorber is ideal for thin-film solar cells, even if this technology could be more competitive with a lower manufacture cost. The fabrication of devices with thinner CIGS absorbers is a way to increase the throughput of a factory and to reduce material consumption. This PhD thesis aims to develop cells with a CIGS thickness below 500 nm instead of the conventional 2.0-2.5 µm. However, as reported in the literature, we observed a decrease in cell performance. We carefully analyzed this effect by the comparison between simulations and sample characterizations: it is attributed, on one hand, to a lack of light absorption in the CIGS layer and, on the other hand, to an increased impact of the back-contact (high recombination and low reflectivity). To resolve these problems, we demonstrated theoretically and experimentally that the use of an alternative back-contact, other than molybdenum, such as a transparent conducting oxide coupled with a light reflector, improves the cell efficiency. To achieve this result, an optimization of the CIGS deposition was necessary. Moreover, we proved that a porous oxide layer inserted between the CIGS and the back-contact limits the charge-carrier recombination and removes some parasitic resistance. Finally, an efficiency of 10.7% was achieved for a 480-nm-thick CIGS solar cell with a SnO2:F back-contact passivated with a porous Al2O3 layer
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Wennerberg, Johan. "Design and Stability of Cu(In,Ga)Se2-Based Solar Cell Modules." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1630.
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Cu(In,Ga)Se2 (CIGS) is one of the most promising semiconductor compounds for large-scale production of efficient, low-cost thin film solar cells, and several research institutes have announced their plans for CIGS production lines. But for the CIGS technology to become a commercial success, a number of issues concerning manufacturability, product definition, and long-term stability require further attention. Several studies indicate that CIGS-based modules are stable over many years in field operation. At the same time, it is shown in the present work that they may have difficulties in passing standard accelerated lifetime test procedures like the IEC 1646 damp heat test. In particular, CIGS modules are sensitive to humidity penetrating through the module encapsulation, which will increase the resistive losses in the front contact and cause severe corrosion of the back contact. It is also shown that cells experience degradation in both voltage and fill factor, and the causes of these effects are addressed. By concentrating the light falling onto a solar cell, the device will deliver a higher power output per illuminated absorber area, which can lower the electricity production costs. For CIGS-based solar cells, low-concentrated illumination could be an economically viable approach. In this work it is shown that the yearly performance of a photovoltaic system with CIGS modules can be significantly improved at a moderate cost by using parabolic aluminum mirrors as concentrating elements. However, in order to avoid detrimental power losses due to high temperatures and current densities, the modules need to be designed for the higher light intensity and to be sufficiently cooled during operation. A design where the front contact of the module is assisted by a metal grid has shown promising results, not only for concentrated illumination but also for normal operation. The benefits are enhanced window processing tolerance and throughput, as well as improved degrees of freedom of the module geometry.
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Lee, Yunmi. "Site- and Enantioselective C-C and C-B Bond Forming Reactions Catalyzed by Cu-, Mg-, Zn-, or Al-based N-Heterocyclic Carbene Complexes." Thesis, Boston College, 2010. http://hdl.handle.net/2345/1165.
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Thesis advisor: Amir H. HoveydaChapter 1. In this chapter, the ability of chiral bidentate N-heterocyclic carbenes (NHCs) to activate alkylmetal reagents directly in order to promote C‒C bond forming reactions in the absence of a Cu salt is presented. Highly regio- and enantioselective Cu-free allylic alkylation reactions of di- and trisubstituted allylic substrates with organomagnesium, organozinc, and organoaluminum reagents are demonstrated. Chiral bidentate sulfonate-bearing NHC-Zn and NHC-Al complexes are isolated and fully characterized. Based on crystal structures of these catalytic complexes, mechanistic details regarding Cu-free allylic alkylations with alkylmetal reagents are proposed. Chapter 2. New methods for efficient and highly enantioselective Cu-catalyzed allylic alkylation reactions of a variety of trisubstituted allylic substrates with alkylmagnesium and alkyl-, aryl-, 2-furyl-, and 2-thiophenylaluminum reagents are presented. Transformations are promoted by a chiral NHC complex in the presence of commercially available, inexpensive and air stable CuCl2*H2O. Enantiomerically enriched compounds containing difficult-to-access all-carbon quaternary stereogenic centers are obtained. Chapter 3. New methods for highly site- and enantioselective Cu-catalyzed allylic alkylation reactions of allylic phosphates with vinylaluminum reagents are presented. The requisite vinylaluminums are prepared by reaction of readily accessible terminal alkynes with DIBAL-H and used directly without further purification. Vinyl additions are promoted in the presence of a chiral bidentate sulfonate-based NHC complex and a Cu salt. The desired SN2' products are obtained in >98% E selectivities, >98% SN2' selectivities, >98% group selectivities (<2% i-Bu addition) and high enantioselectivities. The enantioselective total synthesis of the natural product bakuchiol highlights the versatility of the one-pot hydroalumination/Cu-catalyzed enantioselective allylic vinylation process. Chapter 4. Efficient and highly site-selective Cu-catalyzed hydroboration reactions of 1,2-disubstituted aryl olefins with bis(pinacolato)diboron (B2(pin)2) are presented. Transformations are promoted by an NHC-Cu complex in the presence of MeOH, affording only secondary β-boronate isomers. A Cu-catalyzed method for the synthesis of enantiomerically enriched secondary alkylboronates promoted by chiral NHC complexes is disclosed. Chapter 5. A new method for efficient and site-selective tandem Cu-catalyzed copper-boron additions to terminal alkynes with B2(pin)2 in the presence of an NHC-Cu complex is demonstrated. In a one-pot process, Cu-catalyzed hydroboration of alkynes provides vinylboronates in situ, which undergo a second site-selective hydroboration to afford vicinal diboronates. Highly Enantiomerically enriched diboronates obtained through Cu-catalyzed enantioselective dihydroboration in the presence of chiral bidentate sulfonate-based NHC-Cu complex are obtained. The control of site selectivity in the first-stage hydroboration of alkynes is critical for efficient and highly enantioselective reactions in the tandem dihydroboration. Functionalizations of the vicinal diboronates described herein underline the significance of the current method
Thesis (PhD) — Boston College, 2010
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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Jutteau, Sébastien. "Design, prototyping and characterization of micro-concentrated photovoltaic systems based on Cu(In,Ga) Se2 solar cells." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066666/document.
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Dans cette thèse, nous avons étudié la conception, le prototypage et la caractérisation de microsystèmes photovoltaïques à concentration à base de cellules solaires Cu(In,Ga)Se2. L'objectif est de réduire l'utilisation de matériaux rares en utilisant la concentration de la lumière, et bénéficier des effets de la miniaturisation, comme la dissipation de la chaleur et des pertes résistives inférieurs. Tout d'abord, la conception optique des systèmes à concentration sur la base des microlentilles sphériques est présentée. À l'aide d'un logiciel de tracés de rayon Zemax OpticStudio, nous avons évalué la meilleure combinaison d'éléments, l'épaisseur et les rayons de courbure des lentilles, ainsi que les tolérances de fabrication et de positionnement du système. Un système optique de 1 mm d'épaisseur avec un rapport géométrique de 100 et une tolérance angulaire de +/- 3,5 ° a été conçu. D'autre part, des procédés de fabrication ont été créés et optimisés pour fabriquer un prototype de 5x5 cm² avec 2500 microcellules. Le meilleur mini-module a montré un facteur de concentration de 72x avec une augmentation en valeur absolue de l'efficacité de + 1,6%. Ensuite, des études numériques et expérimentales ont été réalisées sur des systèmes basés sur des concentrateurs luminescents (LSC) et des concentrateurs paraboliques (CPC). Les LSC ont montré un facteur de concentration faible et souffraient de problèmes de répétabilité tandis que les CPC sont une solution très efficace, mais très difficile à fabriquer à l¿échelle du micron. Enfin, nous avons développé un code MATLAB pour estimer l'énergie produite des systèmes conçus, pour évaluer la pertinence des choix technologiques futursIn this thesis, we studied the design, prototyping and characterization of micro-concentrated photovoltaic systems based on Cu(In,Ga)Se2 solar cells. The objective is to reduce the use of rare materials using the concentration of light, and benefit from the effect of miniaturization such as heat dissipation and lower resistive losses. First, the optical design of 1D and 2D concentrating systems based on spherical microlenses is presented. Using a ray-tracing software Zemax OpticStudio, we evaluated the best combination of elements, thickness and radii of curvature of the lenses, as well as the tolerances of fabrication and positioning of the system. An optical system of 1 mm thickness with a geometrical ratio of 100 and an angular tolerance of +/- 3.5° has been designed. Second, fabrication processes have been created and optimized to fabricate a 5x5 cm² prototypes with 2500 microcells. The best mini-module showed a concentration factor of 72x with an absolute increase of the efficiency of +1.6%. Third, numerical and experimental studies have been performed on concentrating systems based on Luminescent Solar Concentrators (LSC) and Compound Parabolic Concentrators (CPC). The LSC showed a low concentration factor and suffered from repeatability issues while the CPC is a very efficient solution but its specific geometry makes it difficult to fabricate at the micron scale. Finally, we developed a MATLAB code to estimate the producible energy of the designed systems, in order to evaluate the relevance of future technological choices that will be made
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Platzer-Björkman, Charlotte. "Band alignment between ZnO-based and Cu(In,Ga)Se₂ thin films for high efficiency solar cells /." Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6263.
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Halbe, Ankush. "CHARACTERIZATION OF MICROSTRUCTURAL AND CHEMICAL FEATURES IN CU-IN-GA-SE-S-BASED THIN-FILM SOLAR CELLS." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2694.
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Thin-film solar cells are potentially low-cost devices to convert sunlight into electricity. Improvements in the conversion efficiencies of these cells reduce material utilization cost and make it commercially viable. Solar cells from the Thin-Film Physics Group, ETH Zurich, Switzerland and the Florida Solar Energy Center (FSEC), UCF were characterized for defects and other microstructural features within the thin-film structure and at the interfaces using transmission electron microscopy (TEM). The present thesis aims to provide a feedback to these groups on their deposition processes to understand the correlations between processing, resulting microstructures, and the conversion efficiencies of these devices. Also, an optical equipment measuring photocurrents from a solar cell was developed for the identification of defect-prone regions of a thin-film solar cell. The focused ion beam (FIB) technique was used to prepare TEM samples. Bright-field TEM along with scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS) including elemental distribution line scans and maps were extensively used for characterizing the absorber layer and interfaces both above and below the absorber layer. Energy-filtered transmission electron microscopy (EFTEM) was applied in cases where EDS results were inconclusive due to the overlap of X-ray energies of certain elements, especially molybdenum and sulfur. Samples from ETH Zurich were characterized for changes in the CIGS (Cu(In,Ga)Se2) microstructure due to sodium incorporation from soda-lime glass or from a post-deposition treatment with NaF as a function of CIGS deposition temperature. The CIGS-CdS interface becomes smoother and the small columnar CIGS grains close to the Mo back contact disappear with increasing CIGS deposition temperature. At 773 K the two sodium incorporation routes result in large differences in the microstructures with a significantly larger grain size for the samples after post-deposition Na incorporation. Porosity was observed in the absorber layer close to the back contact in the samples from FSEC. The reason for porosity could be materials evaporation in the gallium beam of the FIB or a processing effect. The porosity certainly indicates heterogeneities of the composition of the absorber layer near the back contact. A Mo-Se rich layer (possibly MoSe2) was formed at the interface between CIGS/CIGSS and Mo improving the quality of the junction. Other chemical heterogeneities include un-sulfurized Cu-Ga deposits, residual Se from the selenization/ sulfurization chamber in CIGS2 and the formation of Cu-rich regions which are attributed to decomposition effects in the Ga beam of the FIB. Wavy absorber surfaces were observed for some of the cells with occasional discontinuities in the metal grids. The 50 nm thick CdS layer, however, remained continuous in all the samples under investigation. For a sample with a transparent back contact, a 10 nm Mo layer was deposited on ITO (indium tin oxide) before deposition of the CIGS2 (Cu(In,Ga)S2) layer. EFTEM maps indicate that a MoS2 layer does not form for such a Mo/MoS2-ITO back contact. Instead, absorber layer material diffuses through the thin Mo layer onto the ITO forming two layers of CIGS2 on either side of Mo with different compositions. Furthermore, an optical beam induced current (OBIC) system with micron level resolution was successfully developed and preliminary photocurrent maps were acquired to microscopically identify regions within a thin-film solar cell with undesirable microstructural features. Such a system, when fully operational, will provide the means for the identification of special regions from where samples for TEM analysis can be obtained using the FIB technique to study specifically the defects responsible for local variations in solar cell properties.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
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Frisch, Johannes. "Electronic properties of interfaces in polymer based organic photovoltaic cells." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17140.
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Der Schwerpunkt der vorgelegten Arbeit lag in der Bestimmung der Energieniveaus an allen Grenzflächen in bestimmten heterostrukturierten Polymer/Polymer- und Polymer/Molekül basierten Solarzellen. Die elektronische Charakterisierung erfolgte mittels Photoelektronenspektroskopie. Morphologie und Schichtdicke der aufgeschleuderten Filme wurden mit den komplementären Analysetechniken UV-vis Absorptionsspektroskopie, Rasterkraftmikroskopie sowie Röntgenphotoelektronenspektroskopie bestimmt. An der PEDT:PSS-Anode/Polymer-Grenzschicht wurden Änderungen im Vakuumniveau von bis zu 0,65 eV gemessen. Die Polymerabscheidung führte zu einer Erniedrigung der Substrataustrittsarbeit, auch wenn die Polymerionisationsenergie mehrere 100 meV größer als die ursprüngliche PEDT:PSS-Austrittsarbeit war. Eine detailierte Analyse der PEDT:PSS/Polymer Grenzflächen ausgehend von Submonolagen zu Multilagen zeigte verschiedene Ursachen für die Änderungen des Vakuumniveaus als verantwortlich. Zweitens: an Donator/Akzeptor-Grenzflächen wurden Änderungen im Vakuumniveau von bis zu 0,35 eV festgestellt, welche die solare Bandlücke (PVG) und folglich die Höchstgrenze der Leerlaufspannung (VOC) beeinflusst. Ein Vergleich aller Resultate der Grenzflächenanalyse mit den Solarzellen Parametern bestätigte PVG als obere Schranke von VOC. Der Energieunterschied zwischen PVG und VOC, der ein Maß für die Verluste in der Solarzelle darstellt, war für reine Polymerheteroübergänge größer als für Polymer/Molekül-Heterostrukturen mit einem Minimum bei 0,5 eV. Drittens: parallel zum Aufbau der Akzeptor/Kathoden-Grenzfläche veränderte sich das Vakuumniveau um ca. 1 eV, bedingt durch das Pinning des Kathoden-Ferminiveaus (EF) an unbesetzte Grenzflächenzuständen. Die energetische Lage dieser Zustände bezüglich EF entschied dabei über die Stärke der Diffusionsspannung in der Solarzelle, welche bei Beleuchtung der entstandenen Solarzellenstruktur durch eine lichtinduzierte Photospannung ausgeglichen wurde.The main focus of this work was to provide a comprehensive picture of the energy level alignment at the multitude of interfaces that occur in selected polymer/polymer and polymer/small molecule heterojunction photovoltaic cells. The electronic characterization was performed using photoelectron spectroscopy. Morphology and thickness of spin coated thin films was investigated using a complementary technique approach employing UV-vis absorption spectroscopy, atomic force microscopy, and X ray photoelectron spectroscopy. At the PEDT:PSS anode/polymer interface vacuum level shifts up to 0.65 eV were observed. Polymer deposition decreased the substrate work function (WF even though the polymer ionization energy was several 100 meV higher as the initial PEDT:PSS WF. An in depth analysis of the PEDT:PSS/polymer interface from sub-monolayer to multilayer coverage revealed highly diverse origins for the observed vacuum level shifts. Secondly, investigations of the donor/acceptor interfaces revealed vacuum level shifts up to 0.35 eV that influence the photovoltaic gap (PVG) at the heterojunction and, therefore, the upper limit of the open circuit voltage (VOC) in the device. Correlating device data and all results of the interface analysis, PVG was finally confirmed as an upper limit for VOC. The energy difference (eV) between PVG and experimentally determined VOC, which was assigned to losses in the device, was found to be higher for all polymer heterojunctions compared to polymer/small molecule cells with a minimum at eV = 0.5 eV. Third, cathode/acceptor interface formation was accompanied by interfacial vacuum level shifts of ca. 1 eV caused by Fermi level (EF) pinning at interfacial gap states. The exact position of the acceptor pinning level with respect to EF of the anode determines the strength of the built in field in the device that was found to be fully counterbalanced by a photovoltage induced by in situ illumination of the resulting OPVC-like sample structures.
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Deibel, Carsten. "Defect spectroscopy on Cu(In, Ga)(S, Se)2-based heterojunction solar cells role of the damp heat treatment /." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966279530.
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Yu, Zhiqiang. "Transient Studies of Ni-, Cu-Based Electrocatalysts in CH4 Solid Oxide Fuel Cell." Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1194625466.
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Dissertation (Ph. D.)--University of Akron, Dept. of Chemical Engineering, 2007."December, 2007." Title from electronic dissertation title page (viewed 03/12/2008) Advisor, Steven S. C. Chuang; Committee members, Lu-Kwang Ju, Edward Evans, W. B. Arbuckle, Stephen Z. D. Cheng; Department Chair, Lu-Kwang Ju; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Zhang, Xian. "Atmospheric corrosion of zinc-aluminum and copper-based alloys in chloride-rich environments : Microstructure, corrosion initiation, patina evolution and metal release." Doctoral thesis, KTH, Yt- och korrosionsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-151180.
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Fundamental understanding of atmospheric corrosion mechanisms requires an in-depth understanding on the dynamic interaction between corrosive constituents and metal/alloy surfaces. This doctoral study comprises field and laboratory investigations that assess atmospheric corrosion and metal release processes for two different groups of alloys exposed in chloride-rich environments. These groups comprise two commercial Zn-Al alloy coatings on steel, Galfan™ (Zn5Al) and Galvalume™ (Zn55Al), and four copper-based alloys (Cu4Sn, Cu15Zn, Cu40Zn and Cu5Zn5Al). In-depth laboratory investigations were conducted to assess the role of chloride deposition and alloy microstructure on the initial corrosion mechanisms and subsequent corrosion product formation. Comparisons were made with long-term field exposures at unsheltered marine conditions in Brest, France. A multitude of surface sensitive and non-destructive analytical methods were adopted for detailed in-situ and ex-situ analysis to assess corrosion product evolution scenarios for the Zn-Al and the Cu-based alloys. Scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS) were employed for morphological investigations and scanning Kelvin probe force microscopy (SKPFM) for nobility distribution measurements and to gain microstructural information. SEM/EDS, infrared reflection-absorption spectroscopy (IRAS), confocal Raman micro-spectroscopy (CRM) and grazing incidence x-ray diffraction (GIXRD) were utilized to gain information on corrosion product formation and possibly their lateral distribution upon field and laboratory exposures. The multi-analytical approach enabled the exploration of the interplay between the microstructure and corrosion initiation and corrosion product evolution. A clear influence of the microstructure on the initial corrosion product formation was preferentially observed in the zinc-rich phase for both the Zn-Al and the Cu-Zn alloys, processes being triggered by microgalvanic effects. Similar corrosion products were identified upon laboratory exposures with chlorides for both the Zn-Al and the Cu-based alloys as observed after short and long term marine exposures at field conditions. For the Zn-Al alloys the sequence includes the initial formation of ZnO, ZnAl2O4 and/or Al2O3 and subsequent formation of Zn6Al2(OH)16CO3·4H2O, and Zn2Al(OH)6Cl·2H2O and/or Zn5(OH)8Cl2·H2O. The patina of Cu sheet consists of two main layers with Cu2O predominating in the inner layer and Cu2(OH)3Cl in the outer layer, and with a discontinuous presence of CuCl in-between. Additional patina constituents of the Cu-based alloys include SnO2, Zn5(OH)6(CO3)2, Zn6Al2(OH)16CO3·4H2O and Al2O3. General scenarios for the evolution of corrosion products are proposed as well as a corrosion product flaking mechanism for some of the Cu-based alloys upon exposure in chloride-rich atmospheres. The tendency for corrosion product flaking was considerably more pronounced on Cu sheet and Cu4Sn compared with Cu15Zn and Cu5Al5Zn. This difference is explained by the initial formation of zinc- and zinc-aluminum hydroxycarbonates Zn5(OH)6(CO3)2 and Zn6Al2(OH)16CO3·4H2O on Cu15Zn and Cu5Al5Zn, corrosion products that delay the formation of CuCl, a precursor of Cu2(OH)3Cl. As a result, the observed volume expansion during transformation of CuCl to Cu2(OH)3Cl, and the concomitant flaking process of corrosion products, was less severe on Cu15Zn and Cu5Al5Zn compared with Cu and Cu4Sn in chloride-rich environments. The results confirm the barrier effect of poorly soluble zinc and zinc-aluminum hydroxycarbonates Zn5(OH)6(CO3)2 and Zn6Al2(OH)16CO3·4H2O, which results in a reduced interaction between chlorides and surfaces of Cu-based alloys, and thereby reduced formation rates of easily flaked off corrosion products. From this process also follows reduced metal release rates from the Zn-Al alloys.Bättre molekylär förståelse för metallers atmosfäriska korrosion kräver en fördjupad kunskap i det dynamiska samspelet mellan atmosfärens korrosiva beståndsdelar och metallytan. Denna doktorsavhandling omfattar laboratorie- och fältundersökningar av korrosions- och metallfrigöringsprocesser av två grupper av legeringar som exponerats i kloridrika atmosfärsmiljöer: två kommersiella Zn-Al beläggningar på stål, Galfan™ (Zn med 5% Al, förkortat Zn5Al) och Galvalume™ (Zn55Al), samt fyra kopparbaserade legeringar (Cu4Sn, Cu15Zn, Cu40Zn och Cu5Zn5Al). Undersökningar har genomförts i renodlade laboratorie-miljöer med för-deponerade NaCl-partiklar i en atmosfär av varierande relativ fuktighet. Syftet har varit att utvärdera betydelsen av kloriders deposition och legeringarnas mikrostruktur på korrosionsmekanismen samt bildandet av korrosionsprodukter. Jämförelser av korrosionsmekanismer har även gjorts efter flerårsexponeringar av samma legeringar i en marin fältmiljö i Brest, Frankrike. Undersökningarna har baserats på ett brett spektrum av analysmetoder för detaljerade studier dels under pågående atmosfärisk korrosion (in-situ), och dels efter avslutad korrosion (ex-situ). Legeringarnas mikrostruktur och tillhörande variation i ädelhet hos olika faser har undersökts med svepelektronmikroskopi och energidispersiv röntgenmikroanalys (SEM/EDS) samt med en variant av atomkraftsmikroskopi (engelska: scanning Kelvin probe force microscopy, SKPFM). Korrosionsprodukternas tillväxt har analyserats in-situ med infraröd reflektions-absorptionsspektroskopi (IRAS), samt morfologi och sammansättning av bildade korrosionsprodukter ex-situ med SEM/EDS, konfokal Raman mikro-spektroskopi (CRM) samt röntgendiffraktion vid strykande ifall (GIXRD). Det multi-analytiska tillvägagångssättet har medfört att det komplexa samspelet mellan de skilda legeringarnas mikrostruktur, korrosionsinitiering och bildandet av korrosionsprodukter kunnat studeras i detalj. En tydlig påverkan av mikrostruktur på det initiala korrosionsförloppet har kunnat påvisas. Korrosionsinitieringen sker företrädesvis i mer zinkrika faser för såväl Zn-Al- som Cu-Zn-legeringar och orsakas av mikro-galvaniska effekter mellan de mer zinkrika, mindre ädla, faserna och omgivande faser. Deponerade NaCl-partiklar påskyndar den lokala korrosionen oberoende av mikrostruktur. Snarlika sekvenser av korrosionsprodukter har kunnat påvisas såväl efter laboratorie- som fältexponeringar. För Zn-Al-legeringar bildas först ZnO, ZnAl2O4 och/eller Al2O3, därefter Zn6Al2(OH)16CO3·4H2O och Zn2Al(OH)6Cl·2H2O och/eller Zn5(OH)8Cl2·H2O. På ren koppar bildas ett inre skikt dominerat av Cu2O, ett mellanskikt av CuCl och ett yttre skikt med i huvudsak Cu2(OH)3Cl. Beroende på legeringstillsats har även SnO2 och Zn5(OH)6(CO3)2 kunnat identifieras. En mekanism för flagning av korrosionsprodukter på kopparbaserade legeringar i kloridrika atmosfärer har utvecklats. Tendensen för flagning har visat sig vara mycket mer uttalad på ren Cu och Cu4Sn än på Cu15Zn och Cu5Al5Zn. Skillnaden kan förklaras med hjälp av det tidiga bildandet av Zn5(OH)6(CO3)2 och Zn6Al2(OH)16CO3·4H2O på Cu15Zn och Cu5Al5Zn som fördröjer bildandet av CuCl, en föregångare till Cu2(OH)3Cl. Därigenom hämmas även den observerade volymexpansionen som sker när CuCl omvandlas till Cu2(OH)3Cl, en process som visar sig vara den egentliga orsaken till att korrosionsprodukterna flagar. Resultaten bekräftar barriäreffekten hos de mer svårlösliga faserna Zn5(OH)6(CO3)2 och Zn6Al2(OH)16CO3·4H2O, vilken dels resulterar i en minskad växelverkan mellan klorider och de legeringsytor där dessa faser kan bildas, och dels i en reducerad metallfrigöringshastighet.
QC 20140915
Autocorr, RFSR-CT-2009-00015 Corrosion of heterogeneous metal-metal assemblies in the automotive industry
Atmospheric corrosion and environmental metal dispersion from outdoor construction materials
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Insignares, Cristina. "Raman scattering based strategies for assessment of advanced chalcopyrite photovoltaic technologies: Characterisation of electrodeposited Cu(In,Ga)(S,Se)2 solar cells." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/384606.
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The main objective of this thesis is the development of Raman scattering based methodologies for the analysis of advanced electrodeposition-based CIGS technologies, with the identification and characterization of parameters relevant for the efficiency of the solar cells and modules that can be used for quality control and process monitoring applications. The work aims to propose methodologies and tools that can be implemented for the monitoring of the processes at on-line level, contributing to increase the yield and reliability of the processes involved in the fabrication of these devices. The thesis is structured around five papers that have been published in peer-reviewed journals, according to the requirements for the achievement of the degree of Doctor in the Doctoral Program of Engineering and Advanced Technologies in the University of Barcelona.
The thesis is structured in seven chapters. The first chapter is an introduction into Chalcopyrite photovoltaic technologies, including their background, current production strategies and optical characterization by Raman scattering based techniques. The main processes used for the fabrication of the CIGS solar cells and modules are described. Later in the introduction Raman scattering is presented as the main technique used in this work and the approach of this thesis to develop process monitoring techniques to assess parameters for each of the layers in the devices is described. Raman spectra are sensitive to chemico-physical and structural parameters of the layers that determine the device efficiency, as the crystalline quality and presence of defects, the chemical composition, as well as stress and strain effects and presence of secondary phases. The second chapter is dedicated to the disclosure of the Raman experimental set-ups that have been developed and that have been used to obtain the data presented in this work and the experimental conditions chosen to ensure reliability in the measurements. A more detailed description of the application of Raman spectroscopy are disclosed in the following chapters, that address the detection of secondary phases in the absorber layers that are relevant for device performance in high efficiency devices (Chapter 3), the chemical characterization of the surface region of the absorbers (Chapter 4), the assessment of the thickness of the CdS buffer layers (Chapter 5) and the electrical conductivity of the window layers (Chapter 6).
The secondary phases studied in Chapter 2 are the OVC ones in Cu(In,Ga)Se2 alloys and CuAu polytypes in CuInS2 based cells; determining and clarifying their impact on the optoelectronic characteristics of the cells. This work reports for the first time in the literature clear experimental evidences of the impact of the presence of the OVC phases on the optoelectronic characteristics of the cells. Although the efficiencies achieved within CuInS2 (CIS) solar cells are lower (12.7% ) than the yielded by CIGS devices, the larger bandgap of the CIS semiconductor (1.55 eV) gives interest to these devices for the increase of the open circuit voltage Voc. In this work, the role of the presence of CuAu polytypic domains in advanced cells made by electrochemical processes is investigated. The fourth chapter addresses the development of methodologies for the quantitative analysis of the chemical composition of the surface region of the absorber layers, including the Ga/(In+Ga) relative content in Cu(In,Ga)Se2 absorbers and the S/(S+Se) relative content in Cu(In,Ga)(S,Se)2 absorbers. These are the parameters that allow suitable control of the value of the band gap in the surface region of the absorbers. Next chapters address the Raman scattering assessment of the CdS buffer and Al-doped ZnO window layers, being the control of the thickness of the buffer and conductivity of the window layer are relevant for the device efficiency. The final chapter summarizes the main conclusionsEl principal objetivo de esta tesis es el desarrollo de metodologías basadas en la espectroscopia Raman para el análisis de tecnologías fotovoltaicas Cu(In,Ga)(S,Se)2 avanzadas basadas en procesos electroquímicos, con la identificación y caracterización de parámetros relevantes para la eficiencia de las celdas solares y módulos. El trabajo desarrolla y propone metodologías y herramientas que pueden ser implementadas para aplicaciones de control de calidad y monitorización de procesos a nivel "on-line", contribuyendo a incrementar el rendimiento y la fiabilidad de los procesos involucrados en la fabricación de estos dispositivos. La tesis está estructurada en siete capítulos. El primer capítulo es una introducción a las tecnologías fotovoltaicas de la calcopirita, incluyendo las estrategias actuales de producción y su caracterización óptica por medio de técnicas basadas en espectroscopia Raman; más tarde en el capítulo se presenta la espectroscopia Raman como la técnica principal utilizada en el trabajo y se describe el enfoque abordado en la tesis para el desarrollo de técnicas para la monitorización de los procesos. Los espectros Raman permiten obtener información de parámetros estructurales y químico-físicos de las diferentes capas en la estructura que determinan la eficiencia del dispositivo, como la calidad cristalina y presencia de defectos, composición química, estrés y presencia de fases secundarias. El Segundo capítulo describe los sistemas experimentales que se han desarrollado en el trabajo, y las condiciones experimentales determinadas para garantizar la fiabilidad de las medidas. Una descripción más detallada de la aplicación de la espectroscopia Raman se describe en los siguientes capítulos, que abordan la detección de fases secundarias en la capa del absorbedor que son relevantes para la eficiencia de la celda en dispositivos de alta eficiencia (Capítulo 3), la caracterización química de la región superficial de las capas absorbedoras (Capítulo 4), el espesor de las capa buffer de CdS (capítulo 5) y la conductividad eléctrica de las capas ventana (capítulo 6). El último capítulo de la tesis resume las principales conclusiones del trabajo.
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Sáez, Araoz Rodrigo [Verfasser]. "Chemical bath deposition of Zn(S,O) buffer layers and application in Cd-free chalcopyrite-based thin-film solar cells and modules / Rodrigo Sáez Araoz." Berlin : Freie Universität Berlin, 2009. http://d-nb.info/1023816695/34.
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Haug, Annegret Veronika [Verfasser], and H. [Akademischer Betreuer] Kalt. "Properties of the Back Contact Interface for Non-Vacuum Deposited Precursor-Based Cu(In,Ga)Se₂ Solar Cells / Annegret Veronika Haug ; Betreuer: H. Kalt." Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1155474317/34.
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Duren, Stephan van [Verfasser], Aleksander [Akademischer Betreuer] Gurlo, Aleksander [Gutachter] Gurlo, Walter [Gutachter] Reimers, and Thomas [Gutachter] Unold. "Development of in situ methods for process monitoring and control and characterization of Cu-Zn-Sn-S based thin films / Stephan van Duren ; Gutachter: Aleksander Gurlo, Walter Reimers, Thomas Unold ; Betreuer: Aleksander Gurlo." Berlin : Universitätsverlag der TU Berlin, 2019. http://d-nb.info/1187949019/34.
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Hauschild, Dirk [Verfasser], and Friedrich Theodor [Gutachter] Reinert. "Electron and soft x-ray spectroscopy of indium sulfide buffer layers and the interfaces in Cu(In,Ga)(S,Se)2-based thin-film solar cells / Dirk Hauschild. Gutachter: Friedrich Theodor Reinert." Würzburg : Universität Würzburg, 2016. http://d-nb.info/1111784574/34.
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Abid, Fatma. "Contribution à la robustesse et à l'optimisation fiabiliste des structures Uncertainty of shape memory alloy micro-actuator using generalized polynomial chaos methodUncertainty of shape memory alloy micro-actuator using generalized polynomial chaos method Numerical modeling of shape memory alloy problem in presence of perturbation : application to Cu-Al-Zn-Mn specimen An approach for the reliability-based design optimization of shape memory alloy structure Surrogate models for uncertainty analysis of micro-actuator." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMIR24.
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La conception des ouvrages économiques a suscité de nombreux progrès dans les domaines de la modélisation et de l’optimisation, permettant l’analyse de structures de plus en plus complexes. Cependant, les conceptions optimisées sans considérer les incertitudes des paramètres, peuvent ne pas respecter certains critères de fiabilité. Pour assurer le bon fonctionnement de la structure, il est important de prendre en considération l’incertitude dès la phase de conception. Il existe plusieurs théories dans la littérature pour traiter les incertitudes. La théorie de la fiabilité des structures consiste à définir la probabilité de défaillance d’une structure par la probabilité que les conditions de bon fonctionnement ne soient pas respectées. On appelle cette étude l’analyse de la fiabilité. L’intégration de l’analyse de fiabilité dans les problèmes d’optimisation constitue une nouvelle discipline introduisant des critères de fiabilité dans la recherche de la configuration optimale des structures, c’est le domaine de l’optimisation fiabiliste (RBDO). Cette méthodologie de RBDO vise donc à considérer la propagation des incertitudes dans les performances mécaniques en s’appuyant sur une modélisation probabiliste des fluctuations des paramètres d’entrée. Dans ce cadre, ce travail de thèse porte sur l’analyse robuste et l’optimisation fiabiliste des problèmes mécaniques complexes. Il est important de tenir compte des paramètres incertains du système pour assurer une conception robuste. L’objectif de la méthode RBDO est de concevoir une structure afin d’établir un bon compromis entre le coût et l’assurance de fiabilité. Par conséquent, plusieurs méthodes, telles que la méthode hybride et la méthode optimum safety factor, ont été développées pour atteindre cet objectif. Pour remédier à la complexité des problèmes mécaniques complexes comportant des paramètres incertains, des méthodologies spécifiques à cette problématique, tel que les méthodes de méta-modélisation, ont été développées afin de bâtir un modèle de substitution mécanique, qui satisfait en même temps l’efficacité et la précision du modèleThe design of economic system leads to many advances in the fields of modeling and optimization, allowing the analysis of structures more and more complex. However, optimized designs can suffer from uncertain parameters that may not meet certain reliability criteria. To ensure the proper functioning of the structure, it is important to consider uncertainty study is called the reliability analysis. The integration of reliability analysis in optimization problems is a new discipline introducing reliability criteria in the search for the optimal configuration of structures, this is the domain of reliability optimization (RBDO). This RBDO methodology aims to consider the propagation of uncertainties in the mechanical performance by relying on a probabilistic modeling of input parameter fluctuations. In this context, this thesis focuses on a robust analysis and a reliability optimization of complex mechanical problems. It is important to consider the uncertain parameters of the system to ensure a robust design. The objective of the RBDO method is to design a structure in order to establish a good compromise between the cost and the reliability assurance. As a result, several methods, such as the hybrid method and the optimum safety factor method, have been developed to achieve this goal. To address the complexity of complex mechanical problems with uncertain parameters, methodologies specific to this issue, such as meta-modeling methods, have been developed to build a mechanical substitution model, which at the same time satisfies the efficiency and the precision of the model
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Tsao, Hsiang-Wei, and 曹翔崴. "Investigation of Light Soaking Effect on Chemical Bath Deposited Zn(O,S) Buffer Layer-based Cu(In,Ga)(S,Se)2 Thin Film Solar Cells." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/35z5jr.
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Guo, Siao-wei, and 郭筱薇. "Developement of High-temperature Lead-free solders: Zn-Sn-Al-Cu Based Alloy." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/d63szw.
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碩士國立臺灣科技大學
材料科學與工程系
99
Despite numerous studies on the research and development for high-temperature lead free solders, high-lead solder are still in used because high-temperature lead free solders also has been facing several serious problems during these years. Establishing high-temperature lead-free solder is an urgent priority. This study investigates the development of high-temperature lead-free solders and their properties by improve its wettability and oxidation resitivity after addition of Ni and Ge in Zn-Sn-Al-Cu based alloy. The solders are examined for microstructure, thermal properties, mechanical properties and investigate the interfacial reaction between Zn-Sn-Al-Cu based alloy with Cu and Ni/Cu at 300 and 350oC for 1, 2 and 4 hours. The experimental results indicate that the liquilidus temperature of Zn-Sn-Al-Cu based alloys is between 275oC to 375oC with Zn content. As Zn contents increase the (Zn) and CuZn5 increase, therefore resulting in the increase of micro-hardness and ultimate tensile strength and the addition of Al improve mechanical properties. Three or four intermetallic compounds (IMCs) are formed at the interface in the Cu/alloy diffusion couple. The reaction phases are identified as CuZn5, Al4Cu3Zn, ??nphase and CuZn is formed facing to the Cu substrate. The ??nphase is formed or not that is related to Al/Zn ratio. The IMCs are indentified as CuZn5, Al4Cu3Zn, (Zn), (Al) and?n??Sn phase in the alloys near the Ni/Cu substrate after reflow.
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Chien-HungLin and 林建宏. "A Study of Fabricating Cu2ZnSnSe4 Solar Cells by Using Selenization of Cosputtered Cu-Zn-Sn Precursors." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/23196977369703739525.
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碩士國立成功大學
電機工程學系專班
101
The Cu2ZnSnSe4 (CZTSe) is a p-type direct band gap semiconductor with band gap of ~1 eV. Its non toxic, abundant and potential for low cost fabrication are attractive and could be used as an absorber for thin film solar cells. In this thesis, I used co-sputtering method to deposit Copper–Zin-Tin precursors on a soda-lime glass followed by a selenization process to form CZTSe absorber layer. In this study, the influences of the compositions of the precursors, selenazation temperature, and duration on the CZTSe film were investigated. A scanning electron microscopy was used to observe the film’s morphology, crystalline phase and orientation were determined by X-ray diffraction patterns and Raman analysis, and an energy dispersive X-ray spectroscopy was used to analyze the compositions of films and the absorber layer. Finally, CZTSe thin film were fabricated using the following process parameters: stoichiometric but Cu-poor precursor was used followed by a two step selenization process (300℃30 mins and then raise to 530℃ for 30mins). To form the CZTSe thin film solar cell, CZTSe thin film about 2-μm-thick were fabricated followed by sequentially depositing CdS, i-ZnO, Al-doped ZnO (AZO) and Ag electrode on the CZTSe thin film. Conversion efficiency of solar cells were measured, however, no efficiency was obtained from the devices. At the end, reasons of no efficiency is explained and discussed. Methodology to improve solar cell efficiency for future study is suggested.
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Hung, Hui-Tzu, and 洪慧慈. "Adhesive Behavior and Interfacial Reaction between Sn-Zn Based Solders and Metallized Cu Substrates." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/66259602083583707244.
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碩士國立成功大學
材料科學及工程學系碩博士班
92
This research is investigated the interfacial reaction and adhesive behavior between Sn-Zn based solders and metallized Cu substrates. The microstructure and thermal property of Sn-Zn based solders were also studied. The wettability between Sn-Zn based solders and different substrates were investigated with the wetting balance. The adhesive strength between Pb-free solder balls and BGA substrate after reflow process was measured by shear test. The interfacial reaction behavior after dipping and reflow process was investigated by SEM and EPMA. The microstructure of Sn-9Zn alloy consists of ß-Sn matrix and Zn-rich phase. As for Sn-8.55Zn-0.5Ag-0.1Al-0.5Ga alloy, besides the coexistence of ß-Sn matrix and Zn-rich phase, Ag-Zn compound precipitates within the solder matrix. The melting point of Sn-8.55Zn-0.5Ag-0.1Al-0.5Ga alloy was found to be 196.4 ℃. The result of solderability test reveals that the deposition of Sn-Zn based solder on metallized Cu substrate was rough and dull in luster. Sn-8.55Zn-0.5Ag-0.1Al-0.5Ga solder exhibits adequate wettability with the Cu/Ni-P/Au specimen above 250℃. The wetting time is more than 1 sec. Accordingly, the solderability between Sn-8.55Zn-0.5Ag-0.1Al-0.5Ga solder and Au deposited layer needs to be further improved. AuZn3 and Al2Au intermetallic compound(IMC) formed at the interface of Sn-8.55Zn-0.5Ag-0.1Al-0.5Ga solder and Cu/Ni-P/Au after dipping process. After thermal aging, the AuZnx, Al2Au and (Ag.Au)Zn3 formed at the interface. The Ni-P layer does notreact with other element to form IMC. According to the interfacial analysis on the interface between Sn-8.55Zn-0.5Ag-0.1Al-0.5Ga solder and Cu/Au substrate, Al-Au-Zn IMC layer and Cu5Zn8 compound formed at the interface. The shear test data reveals that the adhesive strength of Sn-9Zn solder is higher than that of Sn-8.55Zn-0.5Ag-0.1Al-0.5Ga solder after reflow and longtime thermal aging. The shear strength decreased with increasing aging time. The fracture occurred within the solder balls. In the reflow process, Ag-Zn and Au-Zn compound formed at the interface between Sn-8.55Zn-0.5Ag-0.1Al-0.5Ga solder and BGA substrate. After aged at 150℃ for 1000 hours, Ag-Al-Au and Au-Zn compound formed within solder matrix while Au-Zn and Ni-Zn formed at the substrate side. Al does not react with other element to form IMC.
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Chen, Yu-Cheng, and 陳育徵. "Preparation and properties of nanostructure metal oxide and sulfide (Cu, In, Ni, and Zn) for solar cells." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/9gm6y7.
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博士逢甲大學
電機與通訊工程所
100
In this study, the oxide and sulfide materials of Cu, In, Ni, and Zn are prepared by electrodeposition and annealing methods. For NiSx (x = 2, 1, and 2/3), Ni thin films on ITO glass have been prepared by electrodeposition method. Thin films of NiSx are grown by anneal Ni thin films at different temperatures and sulfur powders. The effects of annealing temperatures and sulfur powders are investigated. For sulfide of copper, copper sulfide (CuS) thin films on ITO glass have been prepared by one-step electrodeposition method. The effect of different electrodeposition current on the structural, morphological, and optical properties of CuS thin films is studied. Moreover, thin films of CuyS (y = 1.75, 1.8, 1.95, and 2.0) are grown by annealing CuS thin films at different temperatures and times. The effects of annealing temperatures and times are investigated. The chalcopyrite CuInS2 thin film is fabricated by sulfured Cu-In alloys. Cu-In alloys are deposited on ITO glass by electrodeposition method. When the Cu-In alloys are fabricated, it is put into a glass tube with the pure sulfur powder together. The structural, morphological, and optical properties of CuInS2 thin films are studied. Indium doped Zinc Oxide (IZO) thin films are deposited by a one-step electrodeposition method on ITO glass from aqueous solution. The aqueous solution of Zn(NO3)2 is fixed at 0.05 M. The effects are studied at different concentration of InCl3, and electrodeposition temperatures and voltages. These materials can be used in solar cells.
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Chang, Wei-En, and 張瑋恩. "Characterization of Electrodes for Cu(In,Ga)Se2-based solar cells." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/22268750716232241790.
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碩士國立東華大學
電機工程學系
97
The electrodes for the Cu(In,Ga)Se2-based solar cells were deposited on the glass substrates by the direct-current magnetron sputtering method in this thesis. The correlations between the sputtering parameters and properties of the deposited films were studied by characterizing the electrical, optical, crystallinity, morphology, and compositional properties. Aluminum-doped zinc oxide films of the front electrodes for the Cu(In,Ga)Se2-based solar cells were deposited on corning 1737 glass substrates with a ZnO/Al2O3 target (Al2O3 2wt.%). The dependences of the carrier concentration, carrier mobility, transmittance, crystallinity, grain size, film stress, surface morphology, and composition of the films on the working voltage, working pressure, substrate temperature, working power, substrate-bias, film thickness, target-substrate distance, and O2/Ar flow ratio were investigated, respectively. The properties of as-deposited aluminum-doped zinc oxide films were analyzed by using the Hall-effect Measurement, UV-VIS Spectrophotometer, X-ray Diffraction, Field Emission Scanning Electron Microscopy, and Energy Dispersive Spectrometer Spectrophotometry. The optimal transparent conductive aluminum-doped zinc oxide films were prepared with a target-substrate distance of 3.5cm, substrate temperature of 200℃, sputtering power of 300W, working pressure of 3m torr, and Ar flux rate of 50 sccm, resulting in the film thickness of 462.5 nm, optical transmittance up to 91.36% in the visible range, and electrical resistivity of down to 7.05 Ω-cm. The back electrodes of molybdenum films were deposited on the soda-lime glass substrates with a molybdenum target (3N5). Both the low resistivity and good adhesion of as-deposited Mo films were obtained by varying the sputtering parameters. The high-quality aluminum-doped zinc oxide and molybdenum films were achieved for the front and back contacts of Cu(In,Ga)Se2-based solar cells, respectively.
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Guo, Yanzhi [Verfasser]. "Synthesis, characterization and catalytic application of Ru/Sn-and Cu/Zn-based nanocomposites / vorgelegt von Yanzhi Guo." 2006. http://d-nb.info/98188833X/34.
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Yu, Chi-Yang, and 游濟陽. "Interfacial Reaction, Microstructure Variation, and Impact Reliability of Sn-based Pb-free Solder Joints with Ni, Cu, and Novel Cu-Zn Under Bump Metallurgy." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/15761939746256173998.
Full textAbstract:
博士國立清華大學
材料科學工程學系
101
In the flip-chip (FC) solder joint, solder alloys usually connect with Ni and Cu based under bump metallurgies (UBMs) at chip-side and substrate-side, respectively. The material selection for solder alloys and UBM material is a critical issue to affect the microstructure, phase formation, and the reliability of the solder joints. In this study, the interfacial reaction, microstructure variation, and impact reliability of Sn-based Pb-free solder joints with Ni, Cu, and novel Cu-Zn UBMs are discussed and categorized into six topics. (1) Microstructural variation and interfacial reaction in Ni/Sn-Ag-Cu/Ni assemblies with and without Ni doping Ni and Cu elements cross-interacted between the Cu and Ni UBMs during thermal aging and affected the interfacial reactions at both Cu and Ni sides. Dual-phased (Cu,Ni)6Sn5 intermetallic compounds (IMCs), which has high and low Ni concentration, formed at the solder/Ni interface. In contrast, thicker low-Ni (Cu,Ni)6Sn5 and thin (Cu,Ni)3Sn layers formed at the Cu side. The Ni doping into solder varied the microstructure of solder alloys and the formation of interfacial IMCs. The re-distribution of Ni and Cu was correlated to the formation mechanism of interfacial (Cu,Ni)6Sn5. (2) Effect of dual-phased (Cu,Ni)6Sn5 IMCs on the impact reliability of Sn-Ag-Cu/Ni solder joints By employing the high-speed shear impact test, the impact fracture morphology reveals that the interface of high-Ni (H)/low-Ni (L) (Cu,Ni)6Sn5 facilitates the crack nucleation within the IMC. It is believed that the crack propagation depends on the fracture toughness of interfacial IMCs. The indentation data shows that bulk H-(Cu,Ni)6Sn5 exhibits distinctly lower fracture toughness than bulk L-(Cu,Ni)6Sn5. In correlating the impact fracture behavior and mechanical properties of two kinds of (Cu,Ni)6Sn5, cracks tend to propagate through H-(Cu,Ni)6Sn5 due to the relatively low fracture toughness of H-(Cu,Ni)6Sn5. (3) Development of a novel Cu-Zn UBM for Pb-free solder joints To suppress the thicker IMCs and voids at the solder/Cu interface, the Cu-Zn alloy was designed for a novel UBM material. The interfacial reactions of Sn/Cu-xZn (x = 0, 15 and 30 at.%) solder joints were investigated. Interestingly, the growth of Cu-Sn IMCs was significantly reduced and no void was found in the Sn/Cu-Zn solder joints after thermal aging. Transmission electron microscopy (TEM) images and the field emission electron probe microanalyzer (FE-EPMA) analysis show that there are two types of Zn-rich phases, i.e. CuZn and Cu-Zn-Sn phases, to form in Sn/Cu-Zn joints. The formation mechanisms of IMCs were probed and proposed with regard to the thermodynamics and kinetics. (4) Liquid-state reaction of Sn-Ag-Cu solders and the novel Cu-Zn UBM During the reflow process, Cu and Zn atoms would dissolve from the Cu-Zn UBM into the molten solders, leading to the variation of the composition in the solders. Then, the composition variation further altered the microstructure of the solders. In comparison with the Sn-Ag-Cu/Cu, it was found that the coarser eutectic region and smaller Cu6Sn5 IMCs inside the solder matrix of Sn-Ag-Cu/Cu-Zn. In addition, the interfacial reaction was also affected by Zn dissolution. In this study, it was demonstrated that the microstructural variation and the phase evolution in the solder joints were controlled by the reflow time and the Zn concentration in the Cu-Zn UBM. (5) Characterization of the Cu6(Sn,Zn)5 intermetallic compound Cu6Sn5 is a dominant IMC at the Sn-based solder/Cu joint interface. The crystal structure of Cu6Sn5 varies with temperature. After reflow at 250 oC, the interfacial Cu6Sn5 revealed hexagonal structure (η-Cu6Sn5). During aging at 150 oC, hexagonal η-Cu6Sn5 would transform into monoclinic η’-Cu6Sn5. According to literature, the phase transformation between η’ and η would induce crack easily propagating through the Cu6Sn5 at the solder joint interface. In the novel solder/Cu-Zn joints, and Zn would dissolve into Cu6Sn5 to form the Cu6(Sn,Zn)5 IMC at the interface. X-ray diffraction and differential scanning calorimetry analyses show that doping small amounts of Zn into Cu6(Sn,Zn)5 can stabilize the hexagonal structure during the thermal aging process. Thermodynamic calculation also demonstrates that Zn can stabilize the hexagonal Cu6(Sn,Zn)5. (6) Application of Cu-Zn UBM on the Ni/Sn-Ag-Cu/Cu-Zn assemblies The feasibility of novel Cu-Zn UBM applied for the Ni/solder/Cu-Zn assemblies was also evaluated. In comparison with the Ni/Sn-Ag-Cu/Cu solder joint, Ni/Sn-Ag-Cu/Cu-Zn solder joints revealed thinner Cu6Sn5-based IMCs at both Ni/Sn-Ag-Cu and Sn-Ag-Cu/Cu-Zn interfaces after aging. (Cu,Ni)6(Sn,Zn)5/(Cu,Ni)6Sn5 dual-phase formed at the Ni side while (Cu,Ni)6(Sn,Zn)5 single-phase at the Cu-Zn side. The interfacial IMCs grew very slowly, and no void formed in these Zn-contained solder joints during thermal aging. Additionally, the dissolved Zn in the solder alloy reduced the elemental cross-interaction between the Ni and Cu-Zn substrates. The noticeable thermal stability of Ni/Sn-Ag-Cu/Cu-Zn solder joints is attributed to the Zn re-distribution retarding the reaction of Ni, Cu and Sn. Phase formation and IMCs suppression mechanisms in Ni/Sn-Ag-Cu/Cu-Zn solder joints were probed and discussed. In summary, novel Cu-Zn UBM shows lots of advantages for soldering, including: (I) reduction of Cu-Sn IMCs, (II) suppression of voids at the interface, (III) formation of the a hexagonal Cu6(Sn,Zn)5, and (IV) retardation of the elemental cross-interaction in the Ni/solder/Cu-Zn assemblies. The Cu-Zn alloys could be a potential UBM material for the advanced electronic packaging.
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"Buffer layers for Cu(In,Ga)Se2 based thin film solar cell." 2014. http://library.cuhk.edu.hk/record=b6115709.
Full textAbstract:
銅銦鎵硒薄膜太陽能電池是一種清潔、環保的發電技術。 最近，銅銦鎵硒太陽能電池實現了20.9%的光電轉換效率，超出了多晶硅太陽能電池所保持的20.4%的薄膜太陽能電池的最高紀錄。 多種技術改進促成了這項薄膜太陽能電池的新紀錄。 其中一種重要改進是將1 到2 微米厚的硫化鎘硫化鋅混合窗口層替換成薄層硫化鎘和摻鋁氧化鋅透明導電層。基於本實驗室在生長高質量銅銦鎵硒吸收層的先進技術，本工作重點研究了位於吸收層和透明窗口層之間的緩衝層和高阻窗口層。 這兩層的常規結構是由化學水浴法生長的硫化鎘層和本征氧化鋅層組成。 本論文的第一部分是關於這種常規結構的參數優化。 經過優化，本實驗室實現了在小型組件（總面積60 平方釐米）上15.6%的最高轉換效率。
本論文的第二部分關於用化學水浴法生長緩衝層。 我們發展了一種新型生長制備，用於避免氣泡和孔洞在吸收層表面的形成。 表面形貌測試結果顯示，使用此種設備生長的緩衝層能均勻的覆蓋銅銦鎵硒吸收層的表面。 其它硫化鎘的生長參數也根據新設備的特點進行了優化。 優化結果顯示，在空間電荷區的復合對電池轉換效率影響較大，而這種復合損失可以經過調整緩衝層與吸收能之間能帶結構得到減少。 我們研究了另外一種用化學水浴法生長的緩衝層：硫化鋅。 硫化鋅是一種無毒的寬禁帶材料，在短波部分有較少的光吸收。因此，它是一種很好的硫化鎘替代物。 我們研究了在不同生長溫度下的生長動力學機制。 最優的生長溫度是95 攝氏度。 經過生長結束後的退火過程，硫化鋅的禁帶寬度由3.61eV 下降到3.2eV。 再經過在氧氣環境中的退火，禁帶寬度可由3.2eV 繼續下降到2.9eV。 在單結電池中，硫化鋅的最優厚度在43 納米到62 納米之間。 在此厚度範圍中，具有硫化鋅緩衝層的電池實現了相對於具有硫化鎘緩衝層的電池更高的轉換效率。硫化鋅電池實現了與硫化鎘電池相近的開路電壓。 此項改進主要是由於在高溫條件下生長的硫化鋅與銅銦鎵硒層形成了更合適的能帶結構。
本論文的第三部分是關於用共濺射的方法生長鋅鎂氧化物緩衝層。 實驗結果顯示，鋅鎂氧化物的晶體結構和禁帶寬度與鎂含量相關。 當鎂含量小於0.4 時，鋅鎂氧化物具有(002)從優方位的纖鋅礦結構。 晶體質量隨鎂含量的增加而降低，同時，鋅鎂氧化物的禁帶寬度隨鎂含量的增加線性增加。 對於濺射方法生長的緩衝層，吸收層的表面鈍化對提高轉化效率非常重要。
本論文的最後一部分是關於高阻窗口層的研究。 相比於由本征氧化鋅構成的高阻窗口層，由鋅鎂氧化物構成的高阻窗口層能使電池有更優的穩定性。對於單結電池，本層的最優厚度是50 納米。對於小型組件，最優厚度在100 納米左右。 關於鎂的最優組分，結果仍爭議，但可以確定的是由較高濺射功率（大於2.2 瓦每平方釐米）產生的濺射損傷是應當盡量避免的。關於光照產生的亞穩定性的研究表明，亞穩定性強度與濺射環境中的氧氣含量正相關。 相對於無氧氣摻雜的電池，通過將1%的氧氣摻入氬氣濺射環境中，電池效率提高了0.5 個百分點。
Cu(In,Ga)Se2 (CIGS)-based thin film solar cells have been regarded as a promising technology for cheap and environmentally friendly electricity generation. CIGS based solar cell has achieved 20.9% conversion effciency, while the offcial record for multicrystalline Silicon solar cell is 20.4%. A series of improvements have lead to this record for thin film based solar cell. An important improvement originated from the replacement of 1- to 2-um-thick doped (Cd,Zn)S layer by a thin, undoped CdS and a transparent conductive oxide(TCO).
Based on our techniques on growing high quality CIGS absorber layer, this work focuses on further optimization of buffer layer and high resistance window layer located between the CIGS absorber and the TCO window layer. The standard buffer structure includes a chemical-bath-deposited CdS layer and an intrinsic ZnO layer. The first part of this thesis is about optimization of this standard structure carried out in our laboratory. The best conversion effciency achieved on mini-module with total area of 60 cm² is 15.6 %.
The second part is about the fabrication of alternative buffer layers by chemical bath deposition. New deposition equipment has been invented to eliminate stationary bubbles and uncovered pinholes on absorber surface in the deposition of CBD CdS. Surface morphology studies shown that the buffer layer grown by this equipment has uniform coverage on the CIGS surface. Other deposition parameters in the chemical bath deposition of CdS buffer layer have been systematically studied employing this new equipment. Our results suggest that the detrimental effect of recombination in SCR region can be mitigated by proper band alignment in the buffer/absorber interface.
Another buffer layer grown by CBD method is ZnS. Because the wider bandgap and less light absorption in short wavelength range, ZnS is a good candidate to replace the toxic CdS buffer layer. The growth kinetics under different deposition temperature have been studied. The optimal temperature profile has been achieved by setting temperature at 95°C. The results of post annealing after deposition indicate that the bandgap energy of CBD ZnS decreases from 3.61 eV to 3.2 eV by annealing in vacuum. A further decrease from 3.2 eV to 2.9 eV could be caused by annealing with oxygen gas. The optimum thickness of ZnS used in single solar cells is between 43nm and 62nm. In this range, devices with CBD-ZnS buffer layer have achieved higher conversion effciency than CBD-CdS buffer layer solar cell. The open circuit voltage for ZnS-buffer devices has approached the value with CdS-buffer. The improvement is mainly due to proper band alignment of ZnS/CIGS interface achieved under high deposition temperature of CBD process.
The third part of this thesis is to study how to deposit (Zn,Mg)O buffer layers by co-sputtering method. It was found that the crystalline structure and optical bandgap of sputtered (Zn,Mg)O varies with Mg concentration. (Zn,Mg)O thin films with Mg concentration less than 0.4 have preferential orientation with a wurtzite phase (002). The crystal quality decreases with increasing Mg concentration and the band gap of the (Zn,Mg)O films has a linear relationship with the Mg concentration in this range. An interesting finding to emerge from this study is that oxygen passivation of absorber surface is critical to improve device performance with (Zn,Mg)O buffer layer deposited by sputtering method.
The last chapter assesses the effect of replacing high resistance window layer with (Zn,Mg)O in devices with CBD-ZnS buffer layer. Compared to devices with i-ZnO (high-resistance window) HRW layer, better device stability has been confirmed on solar cells with (Zn,Mg)O HRW layer. For single cells, the optimum thickness of HRW layer is about 50 nm, and the optimum thickness for mini-modules is around 100nm. Although no conclusion can be drawn with the optimum Mg concentration, the sputtering damage caused by sputtering power density higher than 2.2 W/cm² should be avoided. It was also shown that the metastability effect activated by illumination has positive correlation with the number of energetic oxygen ions in sputtering process. Compared to devices without oxygen doping, a higher effciency (increase of 0.5 % unit) has been achieved by the oxygen/argon doping ratio of 1 %.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Zhu, Jiakuan = 基於銅銦鎵硒薄膜太陽能電池的緩衝層結構研究 / 朱家寬.
Thesis (Ph.D.) Chinese University of Hong Kong, 2014.
Includes bibliographical references (leaves 121-134).
Abstracts also in Chinese.
Zhu, Jiakuan = Ji yu tong yin jia xi bo mo tai yang neng dian chi de huan chong ceng jie gou yan jiu / Zhu Jiakuan.
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Chetty, Raju. "Thermoelectric Propeties of Cu Based Chalcogenide Compounds." Thesis, 2014. http://hdl.handle.net/2005/2912.
Full textAbstract:
Thermoelectric (TE) materials directly convert heat energy into electrical energy. The conversion efficiency of the TE devices depends on the performance of the materials. The conversion efficiency of available thermoelectric materials and devices is low. Therefore, the development of new materials for improving thermoelectric device performance is a highly essential. As the performance of the TE materials depends on TE figure of merit [zT=S2P T ] which consist of three material properties such as Seebeck coefficient (S), electrical resistivity ( ) and thermal conductivity ( ). Thermoelectric figure of merit can be improved by either increase of power factor or decreasing of thermal conductivity or by both. In the present thesis, Cu based chalcogenide compounds are chosen for the study of thermoelectric properties because of their complex crystal structure, which leads to lower values of thermal conductivity. Also, the power factor of these materials can be tuned by the partial substitution doping. In the present thesis, Cu based chalcogenide compounds quaternary chalcogenide compound (Cu2ZnSnSe4), ternary compounds (Cu2SnSe3 and Cu2GeSe3) and tetrahedrite materials (Cu12Sb4S13) have been prepared by solid state synthesis. The prepared compounds are characterized by XRD for the phase identification, Raman Spectroscopy used as complementary technique for XRD, SEM for surface morphology and EPMA for the phase purity and elemental composition analysis respectively. For the evaluation of zT, thermoelectric properties of all the samples have been studied by measuring Seebeck coefficient, resistivity and thermal diffusivity. In the chapter 1, a brief introduction about thermoelectricity and its effects is discussed. Thermoelectric materials parameters such as electrical resistivity, Seebeck coefficient and thermal conductivity for different class of materials are mentioned. The selection of thermoelectric materials and the motivation for choosing the Cu based chalcogenide compounds for thermoelectric applications are discussed.
In chapter 2, the details of the experiments carried out for Cu based chalcogenide compounds are presented.
In chapter 3, the effect on thermoelectric properties by the cation substitution on quaternary chalcogenide compound Cu2+xZnSn1 xSe4 (0, 0.025, 0.05, 0.075, 0.1, 0.125, and 0.15) is studied. The electrical resistivity of all the samples decreases with an increase in Cu content except for Cu21ZnSn09Se4, most likely due to a higher content of the ZnSe. All the samples showed positive Seebeck coefficients indicating that holes are the majority charge carriers. The thermal conductivity of doped samples was higher as compared to Cu2ZnSnSe4 and this may be due to the larger electronic contribution and the presence of the ZnSe phase in the doped samples. The maximum zT = 0.23 at 673 K is obtained for Cu205ZnSn095Se4.
In chapter 4, the effect of multi{substitution of Cu21ZnSn1 xInxSe4 (0, 0.05, 0.075, and 0.1) on transport properties were studied. The Rietveld powder X-ray diffraction data accompanied by electron probe microanalysis (EPMA) and Raman spectra of all the samples con firmed the formation of a tetragonal kesterite structure. The electrical resistivity of all the samples exhibits metallic-like behavior. The positive values of the Seebeck coefficient and the Hall coefficient reveal that holes are the majority charge carriers. The co-doping of copper and indium leads to a significant increase of the electrical resistivity and the Seebeck coefficient as a function of temperature above 650 K. The thermal conductivity of all the samples decreases with increasing temperature. Lattice thermal conductivity is not significantly modified as the doping content may infer negligible mass fluctuation scattering for copper zinc and indium tin substitution. Even though, the power factors (S2 ) of indium-doped samples Cu21ZnSn1 xInxSe4 (x=0.05, 0.075) are almost the same, the maximum zT=0.45 at 773 K was obtained for Cu21Zn09Sn0925In0075Se4 due to its smaller value of thermal conductivity.
In chapter 5, thermoelectric properties of Zn doped ternary compounds Cu2ZnxSn1 xSe3 (x = 0, 0.025, 0.05, 0.075) were studied. The undoped com\pound showed a monoclinic crystal structure as a major phase, while the doped compounds showed a cubic crystal structure confirmed by powder XRD (X-Ray Diffraction). The electrical resistivity decreased up to the samples with Zn content x=0.05 in Cu2ZnxSn1 xSe3, and slightly increased in the sample Cu2Zn0075Sn0925Se3 . This behavior is consistent with the changes in the carrier concentration confirmed by room temperature Hall coefficient data. Temperature dependent electrical resistivity of all samples showed heavily doped semiconductor behavior. All the samples exhibit positive Seebeck coefficient (S) and Hall coefficient indicating that the majority of the carriers are holes. A linear increase in Seebeck coefficient with increase in temperature indicates the degenerate semiconductor behavior. The total thermal conductivity of the doped samples increased with a higher amount of doping, due to the increase in the carrier contribution. The total and lattice thermal conductivity of all samples decreased with increasing of temperature, which points toward the dominance of phonon scattering at high temperatures. The maximum zT = 0.34 at 723 K is obtained for the sample Cu2SnSe3 due to a low thermal conductivity compared to the doped samples.
In chapter 6, thermoelectric properties of Cu2Ge1 xInxSe3 (x = 0, 0.05, 0.1, 0.15) compounds is studied. The powder X-ray diffraction pattern of the undoped sample revealed an orthorhombic phase. The increase in doping content led to the appearance of additional peaks related to cubic and tetragonal phases along with the orthorhombic phase. This may be due to the substitutional disorder created by indium doping. The electrical resistivity ( ) systematically decreased with an increase in doping content, but increased with the temperature indicating a heavily doped semiconductor behavior. A positive Seebeck coefficient (S) of all samples in the entire temperature range reveal holes as predominant charge carriers. Positive Hall coefficient data for the compounds Cu2Ge1 xInxSe3 (x= 0, 0.1) at room temperature (RT) con rm the sign of Seebeck coefficient. The trend of as a function of doping content for the samples Cu2Ge1 xInxSe3 with x = 0 and 0.1 agrees with the measured charge carrier density calculated from Hall data. The total thermal conductivity increased with rising doping content, attributed to an increase in carrier thermal conductivity. The thermal conductivity decreases with increasing temperature, which indicates the dominance of Umklapp phonon scattering at elevated temperatures. The maximum thermoelectric figure of merit (zT) = 0.23 at 723 K was obtained for Cu2In01Ge09Se3.
In chapter 7, thermoelectric properties of Cu12 xMn1 xSb4S13 (x = 0, 0.5, 1.0, 1.5, 2.0) samples were studied. The Rietveld powder XRD pattern and Electron Probe Micro Analysis revealed that all the Mn substituted samples showed a single tetrahedrite phase. The electrical resistivity increased with increasing Mn due to substitution of Mn2+ on the Cu1+ site. The positive Seebeck coefficient for all samples indicates that the dominant carriers are holes. Even though the thermal conductivity decreased as a function of increasing Mn, the thermoelectric figure of merit (zT) decreased, because the decrease of the power factor is stronger than the decrease of the thermal conductivity. The maximum zT = 0.76 at 623 K is obtained for Cu12Sb4S13.
In chapter 8, the summary and conclusion of the present work is presented.
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Chen, Wei-Chao, and 陳韋兆. "Optoelectronic Devices Based on Earth Abundant Element (C, Cu, Zn, Sn, S, Se) by Solution and Vacuum Processes." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/07148918736038028015.
Full textAbstract:
博士國立清華大學
工程與系統科學系
104
This dissertation presents investigations of the design and synthesis of optoelectronic materials with earth abundant element as well as novel experimental design methodologies. First, we developed three different processes to synthesize quaternary chalcogenide compound for solar cell application, including CZTS colloidal nanoparticles (NPs) by microwave assisted heating process, multi-step selenization process, and fast ramping annealing processes. In microwave heating process, we utilize oleylamine (OLA) and trioctylphosphine oxide (TOPO) as the reaction solvents. With appropriate ratio of two complementary solvents, this microwave heating method can shorten the reaction time from 200 min to 10 min with high quality of CZTS NPs. Our results proved that the crystalline CZTS NPs with appropriate stoichiometry and reasonable energy band gap (~1.5 eV) could be achieved. Meanwhile, we also proposed a multi-step selenization process for the Cu-Zn/Sn metallic stacked precursor to prepare Cu2ZnSnSe4 (CZTSe) absorber. Then the reaction in fixed Se vapour pressure in a series of increasing temperatures was studied. By precisely controlling the nucleation temperatures from 150 oC to 500 oC during 4-step selenization, the homogeneity and crystal quality of CZTSe can be achieved, and the binary phase can be totally ruled out. Finally, stoichiometry with less impurity CZTSe thin film formed at the optimum annealing conditions 500 oC for 10 min: lower or higher temperature lead to insufficient crystallization or undesirable phase segregation. A device efficiency of 5.8 % for the CZTSe solar cell have been achieved with an open circuit voltage of 370 mV, short circuit current of 31.99 mA/cm2, and a fill factor of 48.3%. In the third part, we synthesized high quality CZTSSe with fast ramping heating process with multi-stacking metallic layers. We demonstrated that precursor deposition numbers and inter-diffusion issue have a significant effect on the quality of thin film and device performance. The device prepared with conventional 3 layers stacked, with excessive Cu-rich secondary phase iv formation at the back contact region, results in poor performance of devices due to the poor interdiffusion of precursors. By using the modified 9 layer stacked precursor and fast ramping heating process the device efficiency can be improved from 4.8 to 7.7% with open circuit voltage enhancement from 0.44V to 0.5V due to a compact, smooth microstructure, and the suppression of Cu-rich bi-layer formation. Finally, we introduced a new method to fabricate SWNTs network films with high transparent, high electrical conductivity, and uniform in large (10 cm*10 cm) scale by ultrasonic spray. Due to van der Waals' force within individual SWNTs, dispersion of SWNTs in solvent is a challenging issue; therefore, in order to facilitate SWNTs dissolution in solvent, we functionalize surface of SNWTs with conductive polymer. As SWNTs dissolved, we centrifuged the solution, making the bundle SWNTs, amorphous carbon, and well-dispersed SWNTs to be separated. Finally, dispersive SWNTs solution is ultrasonically sprayed, permitting accurate quantity of SWNTs to be deposited onto substrate with large area uniformity, forming ultra-high smoother, high transmission, and high conductivity transparent conductive film. Hopefully, the optical and electrical transport properties of the SWNTs will be appropriate candidate for multiple-junction solar cells, thermo-photovoltaics, and other applications benefiting from a p-type transparent conductor application due to high near-infrared transmission.
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Akhavan, Vahid Atar. "Photovoltaic devices based on Cu(In1-xGax)Se2 nanocrystal inks." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-08-4285.
Full textAbstract:
Thin film copper indium gallium selenide (CIGS) solar cells have exhibited single junction power conversion efficiencies above 20% and have been commercialized. The large scale production of CIGS solar cells, however, is hampered by the relatively high cost and poor stoichiometric control of coevaporating tertiary and quaternary semiconductors in high vacuum. To reduce the overall cost of production, CIGS nanocrystals with predetermined stoichiometry and crystal phase were synthesized in solution.
Colloidal nanocrystals of CIGS provide a novel route for production of electronic devices. Colloidal nanocrystals combine the well understood device physics of inorganic crystalline semiconductors with the solution processability of amorphous organic semiconductors. This approach reduces the overall cost of CIGS manufacturing and can be used to fabricate solar cells on flexible and light-weight plastic substrates.
As deposited CIGS nanocrystal solar cells were fabricated by ambient spray-deposition. Devices with efficiencies of 3.1% under AM1.5 illumination were fabricated. Examining the external and internal quantum efficiency spectrums of the devices reveal that in nanocrystal devices only the space charge region is actively contributing to the extracted photocurrent. The device efficiency of the as-deposited nanocrystal films is presently limited by the small crystalline grains (≈ 15 nm) in the absorber layer and the relatively large interparticle spacing due to the organic capping ligands on the nanocrystal surfaces. Small grains and large interparticle spacing limits high density extraction of electrons and holes from the nanocrystal film. A Mott-Schottky estimation of the space charge region reveals that only 50 nm depth of the nanocrystalline absorber is effectively contributing to the photogenerated current.
One strategy to improve charge collection involves increased space charge region for extraction by vertical stacking of diodes. A much longer absorption path for the photons exists in the space charge region with the stacked devices, increasing the probability that the incident radiation is absorbed and then extracted. This method enables an increase in the collected short circuit current. The overall device efficiency, however, suffers with the increased series resistance and shunt conductance of the device. Growth of nanocrystal grains was deemed necessary to achieve power conversion efficiencies comparable to vapor deposited CIGS films.
Simple thermal treatment of the nanocrystal layers did not contribute to the growth of the crystalline grain size. At the same time, because of the loss of selenium and increased trap density in the absorber layer, there was a measurable decrease in device efficiency with thermal processing.
For increased grain size, the thermal treatment of the absorber layer took place in presence of compensating amounts of selenium vapor. The process of selenization, as it is called, took place at 500°C in a graphite box and led to an increase of the grain size from 15 nm to several microns in diameter. Devices with the increased grain size yielded efficiencies up to 5.1% under AM1.5 radiation. Mott-Schottky analysis of the selenized films revealed a reduction in doping density and a comparable increase in the space-charge region depth with the increased grain size. The increased collection combined with the much higher carrier mobility in the larger grains led to achieved Jsc values greater than 20 mA/cm2.
Light beam induced current microscopy (LBIC) maps of the devices with selenized absorber layers revealed significant heterogeneity in photogenerated current. Distribution of current hotspots in the film corresponded with highly selenized regions of the absorber films. In an effort to improve the overall device efficiency, improvements in the selenization process are necessary. It was determined that the selenization procedure is dependent on the selenization temperature and processing environment. Meanwhile, the reactor geometry and nanocrystal inks composition played important roles in determining selenized film morphology and the resulting device efficiency. Further work is necessary to optimize all the parameters to improve device efficiency even further.text
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Ntholeng, Nthabiseng. "Synthesis and characterization of Cu-based telluride semiconductor materials for application in photovoltaic cells." Thesis, 2017. http://hdl.handle.net/10539/23532.
Full textAbstract:
Submitted to the Faculty of Science, School of Chemistry at University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 05 June 2017.The colloidal method has extensively been used to synthesize ternary and quaternary copper sulfides and selenides. Although tellurides form part of the chalcogenides, little has been reported on them particularly the synthesis of these nanostructures. Achieving high-quality nanocrystals through colloidal synthesis requires thorough monitoring of parameters such as time, solvent, precursor as they affect nucleation and growth of the nanocrystals. Herein, we report on the colloidal synthesis of ternary CuInTe2 and quaternary CuIn1-xGaxTe2 nanostructured semiconductor materials. A typical synthesis of CuInTe2 entailed varying reaction temperature. At temperatures below 250 °C, no formation of CuInTe2 was seen. At 250 °C formation of CuInTe2 could be observed with the formation of binary impurities. A change in the sequence in which precursors were added at 250 °C yielded pure CuInTe2. Applying different surfactants aided in achieving differently structured morphologies of CuInTe2 nanocrystals. Morphology varied from rods, cubes, nanosheets etc. Different morphologies resulted in different optical properties with the high optical band gap of 1.22 eV measured for 1D rods. Different precursors were employed in the synthesis of quaternary CuIn1-xGaxTe2. Precursor 2 (entailed the use of Cu (acac)2, In (acac)3 and Ga(acac)3) yielded pure CuIn1-xGaxTe2 phase with no formation of impurities. Variation in reaction time influenced the optical properties of the quaternary CuIn1-xGaxTe2 with high band gap obtained at low reaction time (30 min). A change in Ga and In concentration resulted in reduced lattice parameters a and c with lowest values obtained with the highest Ga concentration. However, achieving the intended concentration proved challenging due to the loss of the material during synthesis. Increasing the Ga concentration resulted in a high optical band gap. Conducting the reaction with Hexadecylamine (HDA) resulted in a relatively high optical band though the formation of impurities was evident. The obtained band gap can be attributed to small sized particles as evident from TEM results. Heterojunction ZnO/CIT and ZnO/CIGT solar cell devices were fabricated through a simple solution approach. The performance of ZnO/CIGT device was superior to that of ZnO/CIT in which efficiency increased from 0.26-0.78%. In the ZnO/CIT device, high Voc of 880 mV was recorded while 573.66 mV was measured for ZnO/CIGT device. Chemical and thermal treatments were performed on the ZnO/CIGT devices. The efficiency increased from 0.78 1.25% when the device was chemically treated with a short-chain EDT ligand. A high conversion efficiency of 2.14% was recorded for devices annealed at 300 °C. High annealing temperatures resulted in poor device performance with the lowest efficiency of 0.089% obtained at annealing temperatures of 500 °C attributed to the leaching out of In and Ga into the ZnO layer.
LG2017
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"Design of rapid thermal processing system for Cu(In,Ga)Se₂-based solar cells." 2009. http://library.cuhk.edu.hk/record=b5894108.
Full textAbstract:
Yang, Shihang = 銅銦鎵硒太陽能電池中白光退火系統的設計 / 楊世航.Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.
Includes bibliographical references (p. 87-91).
Abstract also in Chinese.
Yang, Shihang = Tong yin jia xi tai yang neng dian chi zhong bai guang tui huo xi tong de she ji / Yang Shihang.
Chapter 1 --- Introduction to Photovoltaics --- p.1
Chapter 1.1 --- "Developments, markets and forecasts" --- p.1
Chapter 1.2 --- The physics of solar cells --- p.2
Chapter 1.2.1 --- Light Absorption --- p.2
Chapter 1.2.2 --- Charge Carrier Separation --- p.6
Chapter 1.2.3 --- Solar Cell I-V Characteristics --- p.7
Chapter 1.3 --- Classifications of Solar Cells --- p.10
Chapter 1.3.1 --- Crystalline silicon solar cell --- p.10
Chapter 1.3.2 --- Thin film solar cells --- p.12
Chapter 1.3.3 --- Organic and polymer solar cells --- p.12
Chapter 1.4 --- "Cu(In,Ga)Se2 Solar Cells" --- p.13
Chapter 1.4.1 --- State of the art --- p.13
Chapter 1.4.2 --- Material properties --- p.14
Chapter 1.4.3 --- Basic processing steps --- p.15
Chapter 2 --- Equipment design --- p.24
Chapter 2.1 --- System design concepts --- p.24
Chapter 2.2 --- Sample transfer chamber --- p.26
Chapter 2.3 --- Co-evaporation chamber --- p.28
Chapter 2.3.1 --- Load-lock chamber --- p.28
Chapter 2.3.2 --- Co-evaporation chamber --- p.31
Chapter 2.4 --- Sputtering chambers --- p.34
Chapter 2.4.1 --- Mo sputtering chamber --- p.34
Chapter 2.4.2 --- Three targets sputtering chamber --- p.36
Chapter 2.5 --- Other chambers --- p.38
Chapter 3 --- Design of Rapid Thermal Processing System --- p.42
Chapter 3.1 --- Introduction to RTP --- p.42
Chapter 3.1.1 --- History and current status of RTP --- p.42
Chapter 3.1.2 --- Advantages of RTP system compared to conventional furnaces --- p.45
Chapter 3.2 --- Computational simulation for RTP system design --- p.47
Chapter 3.2.1 --- Introduction to Ansys Fluent --- p.47
Chapter 3.2.2 --- Model setup steps --- p.54
Chapter 3.2.3 --- Physical principles --- p.57
Chapter 3.2.4 --- Models setup and comparisons --- p.62
Chapter 3.3 --- Rapid thermal processing system --- p.76
Chapter 3.3.1 --- Se deposition chamber --- p.76
Chapter 3.3.2 --- Quartz chamber --- p.78
Chapter 3.3.3 --- Lamp frame --- p.79
Chapter 4 --- Conclusions --- p.83
Chapter 4.1 --- RTP heater design --- p.83
Chapter 4.2 --- Future prospect --- p.83
Bibliography --- p.87
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LIU, YING-CHEN, and 劉瀅溱. "Efficiency Enhancement of Ink-based Cu(In,Ga)Se2 Solar Cells via Indium Incorporation." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/72767116371821321664.
Full text
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Teixeira, Jennifer Cláudia Passos. "Optoelectronic study of Thin Film Solar Cells Based on Chalcogenide." Doctoral thesis, 2019. http://hdl.handle.net/10773/27750.
Full textAbstract:
In this thesis, we studied the role of the defects on the optoelectronic properties of two semiconductors with high potential for photovoltaic application, Cu2ZnSnS4 (CZTS) and Cu(In, Ga)Se2 (CIGS). Both materials are highly doped and strongly compensated, and their optoelectronic properties are governed by a highly complex electronic energy levels structure. In order to further understand the impact of these complex structures on the performance of the devices, several studies were carried out using mainly the photoluminescence technique, and complemented with other optical, morphological, structural, and electrical analyses. For CZTS based solar cells, three series of samples that include studies on the impact of: i) the time of maximum temperature of the sulphurization; ii) the sulphurization method; and iii) the postdeposition annealing on the optoelectronic properties of the CZTS layer, were studied. For CIGS based solar cells, three major topics were addressed: i) solar cells with conventional architecture, ii) solar cells that explore new architectures; and iii) theoretical and experimental study of the influence of defects on the devices performance. The influence of fluctuating potential was shown, and fully explain CZTS and CIGS characteristic luminescence. The optical studies carried in CZTS based solar cells, reveal several issues related to nonradiative recombination or recombination involving deep defects that were closely linked to a poor performance of the studied devices. For different series of CIGS based solar cells, an overall correlation of the influence of the fluctuating potentials with the performance of the devices were obtained. The CIGS related optical results revealed two main recombination deexcitation channels compatible with a shallow donors cluster and the VCu acceptor defect. From
theoretical and experimental analyses of CIGS based solar cells, we obtained a higher degree of correlation of electrostatic fluctuating potentials with the open circuit voltage losses of the devices, in comparison with bandgap fluctuations. Finally, we demonstrate the influence of fluctuating potentials in CIGS technology at room temperature. In this thesis, we showed that the optoelectronic properties of CZTS and CIGS are consistent with the existence of the fluctuating potentials, being its impact as a limitative factor on the studied solar cells performance significantly different in the two studied technologies. CZTS based solar cells present serious recombination issues that are significantly more critical for the performance of the device, then the existence of fluctuating potentials. For CIGS based solar cells, the influence of the
fluctuating potentials and the performance of the devices are remarkably correlated.Nesta tese, foi estudado o papel dos defeitos nas propriedades optoelectrónicas de dois materiais com grande potencial para aplicações fotovoltaicas, Cu2ZnSnS4 (CZTS) e Cu(In, Ga)Se2 (CIGS). Ambos os materiais são fortemente dopados e compensados, sendo que as suas propriedades optoelectrónicas são governadas pelas suas estruturas de níveis eletrónicos complexas. No sentido de melhor compreender o impacto da estrutura eletrónica no desempenho das células solares, diferentes estudos foram realizados utilizando principalmente a técnica de fotoluminescência, complementada com análise morfológica, estrutural e elétrica. Para as células solares baseadas em CZTS, foram estudadas três séries de amostras para as quais o impacto i) do tempo da temperatura máxima de sulfurização, ii) do método de sulfurização, iii) do tratamento térmico após a deposição, foi avaliado nas propriedades optoelectrónicas da camada CZTS. Para o CIGS, três tópicos principais foram abordados, i) células solares com arquitetura convencional, ii) células solares para as quais se exploram novas arquiteturas, iii) influência dos defeitos no desempenho das células solares a partir da comparação de modelos teóricos com resultados experimentais. A influência das flutuações de potencial foi evidenciada, sendo que a luminescência obtida, tanto envolvendo o CZTS como o CIGS, foi completamente explicada a partir de modelos de recombinação que envolvem a presença destas flutuações. Os estudos óticos desenvolvidos no âmbito das células solares de CZTS revelaram um grande impacto de mecanismos não radiativos e de recombinação envolvendo defeitos profundos que se relacionam com um fraco desempenho dos dispositivos estudados. Para diferentes séries de amostras de células solares baseadas em CIGS foi obtida uma correlação entre a influência das flutuações de potencial e desempenho dos dispositivos estudados. Os resultados óticos obtidos para CIGS revelaram dois mecanismos principais de desexcitação dos canais radiativos envolvendo aglomerados de dadores pouco profundos e o defeito aceitador VCu. A partir das análises teórica e experimental de células solares de CIGS, obtevese uma maior correlação entre a influência das flutuações de potencial electroestáticas com as perdas de tensão de circuito aberto, do que aquela observada para as flutuações de hiato. Finalmente, foi demonstrada a influência das flutuações de potencial na tecnologia CIGS à temperatura ambiente. Nesta tese, foi mostrado que as propriedades optoelectrónicas do CZTS e CIGS são consistentes com a existência de flutuações de potencial, sendo que o seu impacto no desempenho das células solares é significativamente diferente em cada uma das tecnologias. Enquanto no CZTS os mecanismos de recombinação aparecem como um problema com um impacto no desempenho das células solares mais significativo que as flutuações de potencial, no CIGS uma correlação entre a influência das flutuações de potencial e o desempenho das células solares é notória.
The author acknowledge the financial support of the project UID/CTM/50025/2019, and IF/00133/2015/CP1325/CT0001 from the FCT.
Programa Doutoral em Física