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1
Grabitz, Peter. "Inhomogene Cu(In,Ga)Se2-Solarzellen". Aachen Shaker, 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-32469.
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2
Rega, Niklas. "Photolumineszenz epitaktischer Cu(In, Ga)Se2-Schichten". [S.l. : s.n.], 2004. http://www.diss.fu-berlin.de/2004/190/index.html.
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3
Dirnstorfer, Ingo. "Untersuchungen an CuIn(Ga)Se2-Dünnschichten und Solarzellen". [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=958260028.
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4
Grabitz, Peter [Verfasser]. "Inhomogene Cu(In,Ga)Se2 Solarzellen / Peter Grabitz". Aachen : Shaker, 2007. http://d-nb.info/1166511669/34.
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5
Schulmeyer, Thomas. "Mechanismen der Grenzflächenausbildung des Cu(In,Ga)Se2-Systems". [S.l.] : [s.n.], 2005. http://elib.tu-darmstadt.de/diss/000617.
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6
Daume, Felix. "Degradation of Flexible Cu(In,Ga)Se2 Solar Cells". Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-189708.
Testo completoAbstract (sommario):
Untersuchungsgegenstand dieser Arbeit ist die Degradation flexibler Dünnschichtsolarzellen auf Basis von Cu(In,Ga)Se2 Absorbern. Zur beschleunigten Alterung unter Laborbedingungen wurden unverkapselte Solarzellen in Klimaschränken Wärme und Feuchte ausgesetzt. Die Auswirkungen von Wärme und Feuchte auf die Solarzellen wurden zunächst durch Messung von Strom–Spannungs–Kennlinien (IV) und Kapazitäts–Spannungs–Charakteristiken (CV) erschlossen. Mittels in–situ Messungen der IV–Kennlinien der Solarzellen unter Wärme und Feuchte konnte die Degradationskinetik untersucht werden. Es gelang zwei Phasen der Alterung, eine anfängliche Verbesserung und die eigentliche Degradation, zu unterscheiden. Außerdem war es dadurch möglich Degradationsraten zu bestimmen. Die Untersuchung der Stabilität der Flächenkontakte erfolgte im Schichtverbund der Solarzelle und separat. Dann wurde der Einfluss von Natrium, einem Bestandteil der Cu(In,Ga)Se2 Solarzellen, untersucht. Schichtzusammensetzung, Elementprofile und Oberflächenbeschaffenheit wurden mittels Laser–induzierter Plasmaspektroskopie (LIBS), Sekundärionen–Massenspektrometrie (SIMS), Rasterelektronenmikroskopie (SEM) und 3D–Lasermikroskopie gemessen. Die Rolle von Natrium für den Degradationsprozess konnte für zwei unterschiedliche Methoden der Natriumeinbringung in den Absorber (Ko–Verdampfung, Nachbehandlung) beschrieben werden. Schließlich wurde mittels Elektrolumineszenz (EL), Thermographie (DLIT) und der Messung Lichtstrahl–induzierter Ströme (LBIC) die Degradation ortsaufgelöst untersucht und Inhomogenitäten detektiert. Aus spannungsabhängigen Elektrolumineszenzaufnahmen gelang es Serienwiderstandskarten zu errechnen. Die Kombination der genannten Messmethoden erlaubte eine Identifizierung dominanter Degradationsprozesse in den flexiblen Cu(In,Ga)Se2 Solarzellen unter Wärme und Feuchte. Unter anderen wurde die Degradation der Grenzfläche zwischen Absorber und Rückkontakt diskutiert. Die Degradationskinetik konnte beschrieben, Solarzelllebensdauern abgeschätzt, die für die Wärme–Feuchte–Stabilität nachteilige Wirkung von Natrium identifiziert und laterale Inhomogenitäten des Degradationsprozesses aufgezeigt werden. Aus der Diskussion der Ergebnisse wurden Vorschläge zur Verbesserung der Wärme–Feuchte–Stabilität abgeleitet.
7
Schleussner, Sebastian Michael. "ZrN Back-Contact Reflectors and Ga Gradients in Cu(In,Ga)Se2 Solar Cells". Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-151402.
Testo completoAbstract (sommario):
Solar cells constitute the most direct way of converting solar energy to electricity, and thin-film solar-cell technologies have lately been growing in importance, allowing the fabrication of less expensive modules that nonetheless have good power-conversion efficiencies. This thesis focuses on solar cells based on Cu(In,Ga)Se2, which is the thin-film technology that has shown the highest conversion efficiency to date, reaching 20.3 % on the laboratory scale. Solar modules still have some way to go to become entirely competitive with existing energy technologies, and there are two possible paths to this goal: Firstly, reducing their manufacturing costs, for instance by minimizing the material usage per module and/or by increasing the throughput of a given factory; and secondly, increasing the power output per module in other words, the module efficiency. The subject matters of this thesis are related to those two approaches. The first issue investigated is the possibility for reducing the thickness of the Cu(In,Ga)Se2 layer and compensating for lost absorption by using a ZrN back reflector. ZrN layers are fabricated by reactive sputtering and I present a method for tuning the sputtering parameters so as to obtain a back reflector with good optical, electrical and mechanical properties. The reflector layer cannot be used directly in CIGS devices, but relatively good devices can be achieved with a precursor providing a homogeneous supply of Na, the addition of a very thin sacrificial Mo layer that allows the formation of a film of MoSe2 passivating the back contact, and optionally a Ga gradient that further keeps electrons away from the back contact. The second field of study concerns the three-stage CIGS coevaporation process, which is widely used in research labs around the world and has yielded small-area cells with highest efficiencies, but has not yet made it to large scale production. My focus lies on the development and the effect of gradients in the [Ga]/[In+Ga] ratio. On the one hand, I investigate 'intrinsic' gradients (ones that form autonomously during the evaporation), and present a formation model based on the differing diffusivity of Ga and In atoms in CIGS and on the development along the quasi-binary tie line between (In,Ga)2Se3 and Cu2Se. On the other hand, I determine how the process should be designed in order to preserve 'extrinsic' gradients due to interdiffusion. Lastly, I examine the electrical effects of Ga-enhancement at the back and at the front of the absorber and of In-enhancement at the front. Over a wide range, In-rich top layers prove to have no or a weakly beneficial effect, while Ga-rich top regions pose a high risk to have a devastating effect on device performance.
8
Meyer, Thorsten. "Reversible Relaxationsphänomene im elektrischen Transport von Cu(In, Ga)Se2". [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=958349983.
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9
Schlenker, Thomas [Verfasser]. "Growth of Cu(In,Ga)Se2 thin films / Thomas Schlenker". Aachen : Shaker, 2005. http://d-nb.info/1186577509/34.
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10
Chen, Rongzhen. "Exploring the Electronic and Optical Properties of Cu(In,Ga) Se2". Licentiate thesis, KTH, Materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160949.
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11
Reyes, Figueroa Pablo. "Deposition and characterization of CIGS layers by multiple deposition techniques". Thesis, Nantes, 2016. http://www.theses.fr/2016NANT4052/document.
Testo completoAbstract (sommario):
Technologies les plus prometteuses pour suivre le défi de la production d'énergie. La première partie de cette mémoire aborde les absorbeurs de CISe préparés par co-évaporation (3 étapes) et l'effet de l'oxygène (ainsi que le sodium) dans les absorbeurs et des cellules solaires. La température du substrat de 1ère étape la plus élevé (400°C), conduit à un rendement maximal de 12% (Voc=460mV, Jsc=37mA/cm2, FF=78,3%). L’oxydation des couches précurseurs de In2Se3 a montré que les oxydations prolongées ont donnée lieu à faibles rendements de cellules solaires. Les cellules de CISe sans Na ont été fortement dégradées après l’oxydation, avec une baisse de Voc (-72%) et de FF (- 45%). La deuxième partie de la mémoire traite avec la croissance des couches de CISe par un procédé hybride (pulvérisation pyrolyse suivie par coévaporation). La croissance est basée sur un processus de co-évaporation en 3 étapes, mais en remplaçant la couche de 1ère étape avec un couche In2Se3 pyrolysée. Il a été montré qu’une couche de CISe de haute qualité peut être obtenue. L’optimisation des conditions de croissance du procédé hybride (régime du Cu) a permis des dispositifs avec un rendement de 11,1%. Une amélioration peut être atteinte par la diminution de la recombinaison au niveau du contact arrièreIn photovoltaics, the thin film Cu(In,Ga)Se2 (CIGSe) technology is one of the most promising technology to keep up with today’s energy production challenge. The first part of this work address the CISe absorbers films prepared by the 3-stage co-evaporation process. Also, the effect of the oxygen (along with sodium) in the CISe absorbers and solar cells is investigated. The highest 1st-stage substrate temperature (400 C) leads to the highest efficiency of 12% (Voc=460mV, Jsc=37 mA/cm2, FF=78.3%). Oxidation of the In2Se3 precursors films showed that long time exposures resulted in low solar cell parameters. The CISe cells without sodium are degraded after oxidation, with a drop in Voc (-72%) and FF (-45%). The second part of the work deals with the growth of CISe films by a hybrid process which involves two deposition techniques, namely spray pyrolysis and co-evaporation. The process is based on a 3-stage coevaporation process but replacing the 1st-stage film with an In2Se3 spray pyrolyzed film. It was shown that highquality CISe films can be obtained. Optimization of the hybrid process growth conditions (Cu regime) allowed solar cells with efficiencies of 11.1% (Voc=438mV, Jsc=37 mA/cm2, FF=67.5%). Further improvement could be achieved by the decrease of recombination at the back contact
12
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.
Testo completoAbstract (sommario):
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.
13
Hünig, Ruben [Verfasser], e M. [Akademischer Betreuer] Powalla. "Lichtmanagement in Cu(In,Ga)Se2- Dünnschichtsolarzellen / Ruben Hünig ; Betreuer: M. Powalla". Karlsruhe : KIT-Bibliothek, 2017. http://d-nb.info/1143026926/34.
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14
Turunen, Marcus. "Gas flow sputtering of Cu(In,Ga)Se2 with extra selenium supply". Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-260684.
Testo completoAbstract (sommario):
In this thesis CIGS absorber layers have been deposited by gas flow sputtering with an extra supply of selenium, a method that displays promise for large scale production because of its one-step sputtering route which deposits low energy particles in a high deposition rate. In this thesis a method was developed where selenium was added to the sputtering process inside the sputter chamber in a controllable manner and in larger amount than done in previous projects. A total of five samples were manufactured with altered evaporation temperatures and an extra supply of selenium which then were finalized to solar cells using the standard baseline process of the Ångström solar center. The characteristics of the CIGS layer and solar cells were analyzed by XRF, IV- and QE measurements. A cell with a conversion efficiency of 11.6 %, Jsc of 27.9 mA/cm2, Voc of 0.63 V and fill factor of 66.2 % was obtained on a 0.5 cm2 cell area without an antireflective coating. All samples contained cells with obtained efficiencies above 10 %, but over the whole samples the efficiencies varied considerably. The samples that were deposited with moderately large selenium evaporation provided the highest efficiencies with a relatively good homogeneity over the substrate. Results show a deficiency of copper in the CIGS films compared to the target composition. The copper content was lower than 70 % expressed in Cu/(Ga+In), which probably resulted in a low diffusion length for electrons, leading to limited cell efficiencies. Through the duration of the thesis issues that concerned the power supply- and the controls to the substrate heaters as well as the control of the evaporation temperature during the depositions arose that required problem solving and needs to be resolved for the future progression of this work. The conclusions drawn from this thesis are that it is possible to vary the temperature of the selenium source and thereby control the amount of selenium that evaporates during the deposition process even though there is a lot of additional heating in the sputter chamber from both the substrate heaters and the sputter source which could affect the ability to control the amount of selenium being evaporated. That the most likely reason for the limited efficiencies is due to the low copper content in the CIGS films and that a larger amount of evaporated selenium compared to previous work did not result in higher obtained efficiencies.
15
Simchi, Hamed. "Back surface studies of Cu(In,Ga)Se2 thin film solar cells". Thesis, University of Delaware, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3642359.
Testo completoAbstract (sommario):
Cu(In,Ga)Se2 thin film solar cells have attracted a lot of interest because they have shown the highest achieved efficiency (21%) among thin film photovoltaic materials, long-term stability, and straightforward optical bandgap engineering by changing relative amounts of present elements in the alloy. Still, there are several opportunities to further improve the performance of the Cu(In,Ga)Se2 devices. The interfaces between layers significantly affect the device performance, and knowledge of their chemical and electronic structures is essential in identifying performance limiting factors. The main goal of this research is to understand the characteristics of the Cu(In,Ga)Se2-back contact interface in order to design ohmic back contacts for Cu(In,Ga)Se2-based solar cells with a range of band gaps and device configurations. The focus is on developing either an opaque or transparent ohmic back contact via surface modification or introduction of buffer layers in the back surface.
In this project, candidate back contact materials have been identified based on modeling of band alignments and surface chemical properties of the absorber layer and back contact. For the first time, MoO3 and WO 3 transparent back contacts were successfully developed for Cu(In,Ga)Se 2 solar cells. The structural, optical, and surface properties of MoO 3 and WO3 were optimized by controlling the oxygen partial pressure during reactive sputtering and post-deposition annealing. Valence band edge energies were also obtained by analysis of the XPS spectra and used to characterize the interface band offsets.
As a result, it became possible to illuminate of the device from the back, resulting in a recently developed "backwall superstrate" device structure that outperforms conventional substrate Cu(In,Ga)Se2 devices in the absorber thickness range 0.1-0.5 µm. Further enhancements were achieved by introducing moderate amounts of Ag into the Cu(In,Ga)Se2 lattice during the co-evaporation method resulting in a 9.7% cell (with 0.3 µm thickness) which has the highest efficiency reported for ultrathin CIGS solar cells to date.
In addition, sulfized back contacts including ITO-S and MoS 2 are compared. Interface properties of different contact layers with (Ag,Cu)(In,Ga)Se2 absorber layers with various Ga/(Ga+In) and Ag/(Ag+Cu) ratios are discussed based on the XPS analysis and thermodynamics of reactions.
16
Malmström, Jonas. "On Generation and Recombination in Cu(In,Ga)Se2 Thin-Film Solar Cells". Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5721.
Testo completoAbstract (sommario):
The solar cell technology based on Cu(In,Ga)Se2 (CIGS) thin-films provides a promising route to cost competitive solar electricity. The standard device structure is ZnO:Al/ZnO/CdS/CIGS/Mo films on a glass substrate, where the first three layers are n-type semiconductors with wide bandgaps, forming a pn-junction with the p-type CIGS absorber layer; the Mo layer serves as a back contact. This thesis deals with analysis of the generation and recombination of electron-hole pairs throughout the device. These processes determine the maximum output power: generation limits the current; recombination limits the voltage. The generation is calculated with an optical model based on complex refractive indices determined for the individual layers. The main features of the optical response of the solar cell can be reproduced with a specular model neglecting scattering. A model including ideally Lambertian scattering at the front and back surface of the CIGS absorber layer is introduced to investigate the possibility to maintain a high current generation with thin absorber layers. The result highlights the relatively poor optical performance of the Mo back contact. TiN and ZrN are explored as alternatives, and improved optical performance is experimentally demonstrated for both materials. The recombination analysis emphasizes that, in general, more than one recombination path of comparable magnitude are operative in parallel. For cells with absorber bandgap increasing from 1.0 eV (CuInSe2) to 1.7 eV (CuGaSe2), a relative increase of interface recombination is found. When these cells are subject to accelerated ageing, degradation is smallest for intermediate bandgaps; an explanation involving different sensitivity to decreased absorber band bending and activation of grain boundaries is suggested. The optical gain with ZrN back contacts is counteracted by increased back contact recombination and contact resistance, but an intermediate layer of MoSe2 is shown to alleviate these problems, allowing for an overall improved efficiency.
17
Djessas, Kamal. "Etude des matériaux photovoltai͏̈ques Cu(Ga,In)Se2 massifs et en couches minces". Montpellier 2, 1993. http://www.theses.fr/1993MON20105.
Testo completoAbstract (sommario):
Les materiaux photovoltaiques cuca#xin#1##xse#2 massifs et en couches minces ont ete etudies. Le materiau massif a ete synthetise par refroidissement lent du liquide. Il a ete analyse aux rayons x, a la microsonde electronique pour determiner la composition, et en luminescence pour determiner le gap. A partir du materiau massif, des couches minces ont ete obtenues avec une technique de transport chimique a courte distance. Une etude thermodynamique de la methode a ete realisee, les equations chimiques du transport determinees, et les enthalpies standard de formation de cuinse#2 et cugase#2 calculees. Les couches minces de cuga#xin#1##xse#2 ont ete caracterisees par les rayons x, la microscopie electronique, la microsonde electronique, l'absorption optique et l'effet hall. Ces etudes nous ont permis de determiner les conditions de depot de couches quasi-stchiometriques
18
Abatchou, Trobayasse Adrien Emmanuel. "Photopiles à hétérostructure (In,Se)-Cu(In,Ga)Se2/SnO2 : fabrication et études". Perpignan, 2001. http://www.theses.fr/2001PERP0371.
Testo completoAbstract (sommario):
Ce travail est une étude de l'hétérostructure Zn/(In,Se)-Cu(In,Ga)Se2/SnO2 et des phénomènes impliqués dans la formation de la jonction. La couche de Cu(In,Ga)Se2 est déposée par une méthode faible coût , le transport chimique à courte distance. La couche de (In,Se) est déposée par sublimation à courte distance. Elle est déposée d'abord isolante puis type n+. Une jonction se crée spontanément près du SnO2 pendant le dépôt de cette couche. Les études de morphologie et XRD des différentes couches de la structure sont présentées et discutées. La structure est étudiée, notamment les caractéristiques I(V), la position de la jonction par EBIC, les profils de concentration par SIMS. Les phénomènes impliqués dans la formation de la jonction sont étudiés et nous pensons qu'elle est due à une diffusion du cuivre à travers la couche absorbeur, créant un gradient de concentration dans cette coucheThis work is a study of Zn/(In,Se)-Cu(In,Ga)Se2/SnO2 heterostructures and phenomena implied in the formation of the junction. The Cu(In,Ga)Se2 layer is deposited by a low cost method, the close spaced vapor transport. The (In,Se) layer is deposited by close-space-sublimation. The layer is first deposited insulating, then n+ type conducting. A junction is created spontaneously close to SnO2 during the deposition of the (In,Se) layer. Morphology and XRD studies of the different layers of the structure are shown and discussed. The structure is studied, in particular the characteristics I(V), the position of the junction by EBIC, the concentration profiles by SIMS. The phenomena implied in the formation of the junction are studied and we think that this junction is probably due to a diffusion of copper through the absorber layer, creating a concentration gradient in this layer
19
Ibdah, Abedl Rahman. "Optical Physics of Cu(In,Ga)Se2 Solar Cells and Their Layer Components". University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1464639374.
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20
Szaniawski, Piotr. "From Light to Dark : Electrical Phenomena in Cu(In,Ga)Se2 Solar Cells". Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-319454.
Testo completoAbstract (sommario):
In Cu(In,Ga)Se2 (CIGS) solar cells the CIGS layer serves as the light absorber, growing naturally p-type. Together with an n-type buffer layer they form a p-n heterojunction. Typically, CdS is used as a buffer, although other, less toxic materials are investigated as alternatives. The intrinsic p-type doping of CIGS layers is the result of complex defect physics. Defect formation energies in CIGS are very low or even negative, which results in extremely high defect concentrations. This leads to many unusual electrical phenomena that can be observed in CIGS devices. This thesis mostly focuses on three of these phenomena: light-soaking, light-on-bias, and light-enhanced reverse breakdown. Light-soaking is a treatment that involves illuminating the investigated device for an extended period of time. In most CIGS solar cells it results in an improvement of open-circuit voltage, fill factor, and efficiency that can persist for hours, if not days. The interplay between light-soaking and the remaining two phenomena was studied. It was found that light-soaking has a strong effect on light-on-bias behavior, while the results for light-enhanced breakdown were inconclusive, suggesting little to no impact. Light-on-bias is a treatment which combines simultaneous illumination and application of reverse bias to the studied sample. Illuminating CdS-based samples with red light while applying a reverse bias results in a significant increase in capacitance due to filling of traps. In many cases, this is accompanied by a decrease in device performance under red illumination. Complete recovery is possible by illuminating the treated sample with blue light, which causes hole injection from the CdS buffer. In samples with alternative buffer layers, there is little distinction between red and blue illumination, and the increase in capacitance is milder. At the same time, there is little effect on device performance. Reverse breakdown can occur when a sufficiently large reverse bias is applied to a p-n junction, causing a large reverse current to flow through the device. In CIGS solar cells, the voltage at which breakdown occurs in darkness decreases in the presence of blue illumination. A model explaining the breakdown in darkness was proposed as a part of this thesis. The model assumes that all voltage drops on the buffer layer in darkness and on the CIGS layer under blue illumination. The high electric field in the buffer facilitates Poole-Frenkel conduction and Fowler-Nordheim tunneling between the absorber and the buffer.
21
Frisk, Christopher. "Modeling and electrical characterization of Cu(In,Ga)Se2 and Cu2ZnSnS4 solar cells". Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-320308.
Testo completoAbstract (sommario):
In this thesis, modeling and electrical characterization have been performed on Cu(In,Ga)Se2 (CIGS) and Cu2ZnSnS4 (CZTS) thin film solar cells, with the aim to investigate potential improvements to power conversion efficiency for respective technology. The modeling was primarily done in SCAPS, and current-voltage (J-V), quantum efficiency (QE) and capacitance-voltage (C-V) were the primary characterization methods. In CIGS, models of a 19.2 % efficient reference device were created by fitting simulations of J-V and QE to corresponding experimental data. Within the models, single and double GGI = Ga/(Ga+In) gradients through the absorber layer were optimized yielding up to 2 % absolute increase in efficiency, compared to the reference models. For CIGS solar cells of this performance level, electron diffusion length (Ln) is comparable to absorber thickness. Thus, increasing GGI towards the back contact acts as passivation and constitutes largest part of the efficiency increase. For further efficiency increase, majority bottlenecks to improve are optical losses and electron lifetime in the CIGS. In a CZTS model of a 6.7 % reference device, bandgap (Eg) fluctuations and interface recombination were shown to be the majority limit to open circuit voltage (Voc), and Shockley-Read-Hall (SRH) recombination limiting Ln and thus being the majority limit to short-circuit current and fill-factor. Combined, Eg fluctuations and interface recombination cause about 10 % absolute loss in efficiency, and SRH recombination about 9 % loss, compared to an ideal system. Part of the Voc-deficit originates from a cliff-type conduction band offset (CBO) between CZTS and the standard CdS buffer layer, and the energy of the dominant recombination path (EA) is around 1 eV, well below Eg for CZTS. However, it was shown that the CBO could be adjusted and improved with Zn1-xSnxOy buffer layers. Best results gave EA = 1.36 eV, close to Eg = 1.3-1.35 eV for CZTS as given by photoluminescence, and the Voc-deficit decreased almost 100 mV. Experimentally by varying the absorber layer thickness in CZTS devices, the efficiency saturated at <1 μm, due to short Ln, expected to be 250-500 nm, and narrow depletion width, commonly of the order 100 nm in in-house CZTS. Doping concentration (NA) determines depletion width, but is critical to device performance in general. To better estimate NA with C-V, ZnS and CZTS sandwich structures were created, and in conjunction with simulations it was seen that the capacitance extracted from CZTS is heavily frequency dependent. Moreover, it was shown that C-V characterization of full solar cells may underestimate NA greatly, meaning that the simple sandwich structure might be preferable in this type of analysis. Finally, a model of the Cu2ZnSn(S,Se)4 was created to study the effect of S/(S+Se) gradients, in a similar manner to the GGI gradients in CIGS. With lower Eg and higher mobility for pure selenides, compared to pure sulfides, it was seen that increasing S/(S+Se) towards the back contact improves efficiency with about 1 % absolute, compared to the best ungraded model where S/(S+Se) = 0.25. Minimizing Eg fluctuation in CZTS in conjunction with suitable buffer layers, and improving Ln in all sulfo-selenides, are needed to bring these technologies into the commercial realm.
22
Witte, Wolfram [Verfasser]. "Mikroskopische Inhomogenitäten und opto-elektronische Eigenschaften von Cu(In,Ga)Se2-Schichten / Wolfram Witte". Aachen : Shaker, 2011. http://d-nb.info/1075437709/34.
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23
Engelhardt, Frank. "Defektspektroskopie an Solarzellen und Schottky-Kontakten auf Basis des Halbleiters Cu(In, Ga)Se2". [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=958422869.
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Köntges, Marc. "Beleuchtungsabhängiger Ladungstransport durch tiefe kompensierende Störstellen in CdTe- und Cu(In, Ga)Se2-Solarzellen". [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966035062.
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Bhatt, Rita. "Growth and Characterization of ZnO for the Front Contact of Cu(In,Ga)Se2". Scholar Commons, 2000. http://scholarcommons.usf.edu/etd/3840.
Testo completoAbstract (sommario):
ZnO window layers for CIGS solar cells are grown with a DC sputtering technique instead of a conventional RF sputtering technique. Transparent window layers and buffer layers are sputtered from the Zn target in the presence of Oxygen. The window layer is doped with Aluminum in order to achieve high electrical conductivity and thermal stability. The effect of different sputtering parameters on the electrical and optical properties of the films is elaborately studied. Sets of annealing experiments are also performed. Combinations of different deposition parameters are examined to design the optimum fabrication conditions. We are able to deposit 85% transparent, Al doped ZnO films having 002-axis orientation and 4e-4 ohm-cm resistivity, which is successfully, used on CIGS solar cells. Resistivity of undoped ZnO buffer layers is varied form 10-2 ohm-cm to unmeasurable by varying the sputtering parameters. The performance of a reactively sputtered window layer and a buffer layer have matched the performance of the RF sputtered ZnO on CIGS solar cells. There has been considerable effort to eliminate Chemical Bath Deposition of the CdS buffer layer from CIS solar cell fabrication. The performance of an undoped DC sputtered ZnO layer is examined on Cd free CIGS solar cells. The ZnO buffer layer is directly sputtered on an underlying CIGS material. The performance of Cd free solar cells is highly susceptible to the presence of Oxygen in the sputtering ambient of the buffer layer deposition [6]. As Oxygen is a growth component in reactive sputtering, the growth mechanisms of the DC-sputtered buffer layer are studied to improve the understanding. The performance of all reactively sputtered ZnO devices matched the values reported in the literature and the results for DC sputtered ZnO on Cd-free solar cells were encouraging.
26
Ahmad, E. "Growth and characterisation of Cu(In,Ga)Se2 thin films for solar cell applications". Thesis, University of Salford, 1995. http://usir.salford.ac.uk/2173/.
Testo completoAbstract (sommario):
The development of low cost, efficient photovoltaic devices is a major technological challenge which demands suitable materials and fabrication processes. Thin film polycrystalline heterojunction solar cells appear to be most appropriate with respect to cost and ease of manufacture, and it is anticipated that the next generation of photovoltaic devices will be based entirely on thin film technologies. Copper based ternary and multinary compounds are well established as exceptional semiconductors with potential applications in the fields of solar cells for both terrestrial and space applications, infra-red detectors, light emitting diodes etc. The chalcopyrite forms of these compounds have large absorption coefficients and exhibit superior radiation resistance. Among these compounds, CuInSe2 (CIS) and CuIn1-xGaSe2 (CIGS) have raised the most interest and recent thin film heterojunction photovoltaic devices based on these materials have achieved efficiencies of the order 15.5% and 16.9% respectively. The higher efficiencies realised in CIGS based devices is due to the fact that the band gap of the material can be adjusted to wards the optimum value (1.45eV) by the partial substitution of gallium for indium. In this work, thin films of both CIS and CIGS were deposited onto glass substrates by flash evaporation of the respective pre-reacted source materials. The substrate temperature was varied between room temperature and 200 degrees C. Two types of evaporation sources, a flat tungsten strip and a molybdenum twin chimney were used. The effect of the growth conditions on the film properties was observed. The structural, compositional and electro-optical properties were studied using a variety of analytical techniques including x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis with x-ray (EDAX), x-ray fluorescence (XRF), Rutherford backscattering spectroscopy (RBS), four point and thennal probe techniques, photoconductivity (PC) and photoacoustic spectroscopy (PAS). The as-grown films were found to have a columnar structure and a strong preferred orientation with the <112> plane parallel to the substrate. Results from EDAX, XRF and RBS indicated that the as-grown films were slightly deficient in selenium, otherwise the composition was comparable with that of the starting polycrystalline material. Electrical measurements revealed both n- and p-type conductivities with resistivity values in the range 10-2 to 106 gcm. The as-grown films were subsequently processed under several sets of conditions including vacuum, selenium, inert and forming gas ambients at different temperature and times. A two stage post-deposition heat treatment of the films was developed to improve the composition and crystal structure and to optimise the electro-optical properties. It was observed that the first annealing stage (in a selenium ambient) produced an excellent improvement in the composition of the film. An increase in the film grain size (to > 2pm) was observed when the films were subsequently annealed in a forming gas ambient. Significant improvements were also observed in the optical properties. The as-grown and annealed films were analysed using the PAS technique which revealed the existence of several donor and acceptor states originating from intrinsic defect levels. The results were compared with those obtained from single crystals. Photoconductivity measurements were also performed on the as-grown thin films.
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Rolihlahla, Bangile Noel. "Electrochemistry and photophysics of carbon nanodots-decorated nigs(Ni(In, Ga)Se2) quantum dots". university of western cape, 2020. http://hdl.handle.net/11394/7309.
Testo completoAbstract (sommario):
>Magister Scientiae - MScCurrently, non-renewable sources are mostly used to meet the ever-growing demand for energy. However, these sources are not sustainable. In addition to these energy sources being not sustainable, they are bad for the environment although the energy supply sectors highly depend on them. To address such issues the use of renewable energy sources has been proven to be beneficial for the supply of energy for the global population and its energy needs. Advantageous over non-renewable sources, renewable energy plays a crucial role in minimizing the use of fossil fuel and reduces greenhouse gases. Minimizing use of fossil fuels and greenhouse gases is important, because it helps in the fight against climate change. The use of renewable energy sources can also lead to less air pollution and improved air quality. Although solar energy is the most abundant source of renewable energy that can be converted into electrical energy using various techniques, there are some limitations. Among these techniques are photovoltaic cells which are challenged by low efficiencies and high costs of material fabrication. Hence, current research and innovations are sought towards the reduction of costs and increasing the efficiency of the renewable energy conversion devices.
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Sterner, Jan. "ALD Buffer Layer Growth and Interface Formation on Cu(In,Ga)Se2 Solar Cell Absorbers". Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4009.
Testo completoAbstract (sommario):
Cu(In,Ga)Se2 (CIGS) thin film solar cells contain a thin layer of CdS. To avoid toxic heavy-metal-containing waste in the module production the development of a cadmium-free buffer layer is desirable. This thesis considers alternative Cd-free buffer materials deposited by Atomic Layer Deposition (ALD). Conditions of the CIGS surface necessary for ALD growth are investigated and the heterojunction interface is characterized by band alignment studies of ZnO/CIGS and In2S3/CIGS interfaces. The thesis also includes investigations on the surface modification of the CIGS absorber by sulfurization. According to ALD theory the growth process is limited by surface saturated reactions. The ALD growth on CIGS substrates shows nucleation failure and generally suffers from surface contaminations of the CIGS layer. The grade of growth disturbance varies for different ALD precursors. The presence of surface contaminants is related to the substrate age and sodium content. Improved growth behavior is demonstrated by different pretreatment procedures. The alignment of the energy bands in the buffer/absorber interface is an important parameter for minimization of the losses in a solar cell. The valence band and conduction band offsets was determined by in situ X-ray and UV photoelectron spectroscopy during layer by layer formation of buffer material. The conduction band offset (ΔEc) should be small but positive for optimal solar cell electrical performance according to theory. The conduction band offset was determined for the ALD ZnO/CIGS interface (ΔEc = -0.2 eV) and the ALD In2S3/CIGS interface (ΔEc = -0.25 eV). A high temperature process for bandgap grading and a low temperature process for surface passivation by post deposition sulfurization in H2S were investigated. It is concluded that the high temperature sulfurization of CuIn(1-x)GaxSe2 leads to phase separation when x>0. The low temperature process did not result in enhanced device performance.
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Schöldström, Jens. "Thermal Radiation from Co-evaporated Cu(In,Ga)Se2 : End point detection and process control". Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-170437.
Testo completoAbstract (sommario):
The use of solar cells for energy production has indeed a bright future. Reduction of cost for fabrication along with increased efficiency are key features for a market boom, both achieved as a result of increased knowledge of the technology. Especially the thin film solar cell technology with absorbers made of Cu(In,Ga)Se2 (CIGS) is promising since it has proven high power conversion efficiency in combination with a true potential for low cost fabrication. In this thesis different recipes for fabrication of the Cu(In,Ga)Se2 absorber layer have been studied. The deposition technique used has been co-evaporation from elemental sources. For all depositions the substrate has been heated to a constant temperature of 500 ºC in order for the growing absorber to form a chalcopyrite phase, necessary for the photovoltaic functionality. The selenium has been evaporated such to always be in excess during depositions whereas the metal ratio Cu/(In+Ga) has been varied according to different recipes but always to be less than one at the end of the process. In the work emphasis has been on the radiative properties of the CIGS film during growth. The substrate heater has been temperature controlled to maintain the constant set temperature of the substrate, regardless of varying emitted power caused by changing surface emissivity. Depending on the growth conditions the emissivity of the growing film is changing, leading to a readable variation in the electrical power to the substrate heater. Since the thermal radiation from the substrate during growth has been of central focus, this has been studied in detail. For this reason the substrate has been treated as an optical stack composed of glass/Mo/Cu(In,Ga)Se2/CuxSe which determine the thermally radiated power by its emissivity. An optical model has been adopted to simulate the emissivity of the stack. In order to use the model, the optical constants for Cu(In,Ga)Se2 and CuxSe have been derived for the wavelength interval 2 μm to 20 μm. The simulation of the emissivity of the stack during CIGS growth agreed well with what has been seen for actual growth. Features of the OP-signal could hereby be explained as a result of film thickness of Cu(In,Ga)Se2 and CuxSe respectively. This is an important knowledge for an efficient fabrication in large scale.
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Hedlund, Daniel. "Ammonia free CdS buffer layerfor Cu(In,Ga)Se2 solar cells by chemical bath deposition". Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-206786.
Testo completoAbstract (sommario):
The buffer layer in Cu(In,Ga)Se2 solar cells can improve cell performance. In this work we make CdS buffer layer by chemical bath deposition (CBD) without ammonia. CBD without ammonia were sought out since ammonia is a volatile compound. Different recipes for making CdS were tested; only one of the tested recipes actually produced something that is worth further investigating. This recipe used sodium citrate, an innocuous compound instead of ammonia. The best performance was 0.15 % off from the reference.This is almost as good as the used baseline process. However the worst almost completely killed the solar cells. Cell performance dropped by more than absolute 10 %. This demonstrates that chemical bath deposition can have profound effects on the solar cell performance. When trying to improve the best cells only detrimental effects showed up. This might show that, a part in the recipe used, NaOH has detrimental effects on solar cells. Ammonia free chemical bath deposition is possible, however so far it has not produced as good results as the reference. The difference is however very small, which makes it worth further investigating with moreand better solar cell material.
31
Scheit, Christian [Verfasser]. "Experimentelle Untersuchungen zur Kontaktierung flexibler Cu(In,Ga)Se2-Dünnschichtsolarzellen mittels polymerer Dickschichttechnik / Christian Scheit". München : Verlag Dr. Hut, 2013. http://d-nb.info/104389246X/34.
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Weinert, Kristin. "Einfluss von Protonen- und Elektronenbestrahlungen auf die photovoltaischen Parameter von Cu(In, Ga)Se2-Solarzellen". [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11244198.
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Reinhard, Manuel [Verfasser]. "Hybride Dünnschichtphotovoltaik auf der Basis von Cu(In,Ga)Se2 und organischen Halbleitern / Manuel Reinhard". Karlsruhe : KIT Scientific Publishing, 2013. http://www.ksp.kit.edu.
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Pan, Jie. "Material property study on dye sensitized solar cells and cu(ga,in)se2 solar cells". Oxford, Ohio : Miami University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1240594917.
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Lorthioir, Justine. "Architecture alternative de modules photovoltaïques à base de couches minces de Cu(In,Ga)Se2". Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4079.
Testo completoAbstract (sommario):
Un des principaux freins au développement industriel de la filière photovoltaïque à base de couches minces de Cu(In,Ga)Se2 (CIGSe) est son manque de maturité technologique, alors que les rendements atteints des cellules n’ont jamais été aussi élevés, à savoir 23,3% à l’échelle du laboratoire. Ce travail de thèse propose de lever un des verrous technologiques identifié à savoir un écart important entre les performances des cellules et celles des modules. Ces pertes sont inhérentes à l’interconnexion monolithique (réalisée à l’aide des gravures P1, P2 et P3 de manière standard) qui induit (i) une réduction de la surface active des panneaux, (ii) des pertes optiques ainsi que (iii) des pertes résistives. Afin de réaliser des mini-modules à hauts rendements, une architecture alternative a été étudiée et comparée à la structure conventionnelle. Dans cette structure, les grilles métalliques utilisées pour le contact avant du dispositif servent également à connecter de manière monolithique les cellules adjacentes. Ces travaux ont permis de prouver de manière théorique et expérimentale que cette architecture permettait d’obtenir des résultats bien plus intéressants que le design standard. Un des avantages mis en évidence est la réduction de l’épaisseur de la couche fenêtre permettant ainsi la diminution des pertes optiques et résistives. Seulement, une différence subsiste : le module présente une tension de circuit ouvert plus faible que la cellule photovoltaïque. Cette différence peut être due à la croissance de l’absorbeur de Cu(In,Ga)Se2 sur verre qui est découvert lors de la gravure P1. Celle-ci engendrerait des propriétés de CIGSe différentes tant au niveau de sa morphologie, de sa composition que de sa structure cristalline. Enfin, les meilleurs résultats obtenus montrent un rendement de 17,2% pour le module alternatif (avec un facteur de forme de 81%), contre 16,4% (avec un facteur de forme de 75%) pour la cellule. Ce résultat prometteur ouvre de nouvelles voies pour réduire l'écart observé entre les cellules en laboratoire et les modules industrielsOne of the main drawbacks to industrially develop the CIGSe thin-film solar cells in the photovoltaic market is the lack of technological maturity, since the CIGSe lab-scale conversion efficiency has never been higher (23.3%). In this thesis, we address the key problem of the performance gap between the cells and the modules. These losses are due to the monolithic interconnection (carried out using the standard engravings P1, P2 and P3) which induces (i) a reduction of the active surface of the panels, (ii) optical losses as well as (iii) resistive losses. In order to create high-efficiency minimodules, an alternative architecture has been studied and compared to the conventional structure. In this structure, the metal grids, normally used for the front contact, are also used to monolithically connect the adjacent cells. Our work confirms experimentally and theoretically that these alternative modules lead to better photovoltaic performances that the modules with the standard design. One of the advantages highlighted in this thesis, is the reduction of the window layer thickness which enables to further decrease the optical and resistive losses. The only remaining difference between the photovoltaic cell and the module is the lower open circuit voltage of the module. This difference may be due to the fact that a part of the CIGSe layer grows on glass which is uncovered during the P1 etching. This leads to a different CIGSe morphology, composition and crystal structure. Finally, our results show a 17.2% best lab-scale conversion efficiency for the alternative module (with a fill factor of 81%), against 16.4% for the cells (with a fill factor of 75%). These very promising results open new horizons and ways to further improve the observed performance gap between the solar cells made at the laboratory and the industrial modules
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Clolus, Elisabeth. "Étude photoélectrochimique de couches minces semiconductrices polycristallines de Cu(In,Ga)Se2 en milieu aqueux". Paris 6, 2003. http://www.theses.fr/2003PA066061.
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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.
Testo completoAbstract (sommario):
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
38
Pan, Jie. "MATERIAL PROPERTY STUDY ON DYE SENSITIZED SOLAR CELLS AND CU(GA,IN)SE2 SOLAR CELLS". Miami University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=miami1240594917.
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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.
Testo completoAbstract (sommario):
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
40
Ribeaucourt, Lydie. "Electrodépôt et sélénisation d'alliages Cu-In-Ga en vue de la synthèse de couches minces de Cu(In,Ga)Se2 pour cellules solaires". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://pastel.archives-ouvertes.fr/pastel-00649779.
Testo completoAbstract (sommario):
Les cellules solaires à base de couches minces de Cu(In,Ga)Se2 (CIGS), préparées par co-évaporation, atteignent des rendements de conversion jusqu'à 20%. Le développement de méthodes de synthèse telles que l'électrodépôt devrait permettre d'abaisser les coûts de production. Ce travail présente une étude de l'électrodépôt d'alliages Cu-In-Ga en milieu acide aqueux sur substrat de verre recouvert de molybdène. La sélénisation thermique entre 400°C et 600°C permet de former le CIGS. Après une étude bibliographique sur les méthodes de synthèse de CIGS (chapitre 1), les techniques expérimentales utilisées sont décrites dans le chapitre 2. Le chapitre 3 est consacré à l'étude des conditions d'électrodépôt des alliages Cu-In-Ga, à partir d'une analyse de chimie des solutions, puis d'études dédiées dans les électrolytes élémentaires, binaires et ternaires par voltampérométrie. L'analyse chimique et structurale des dépôts permet de corréler le comportement électrochimique avec la présence de phases particulières, notamment Cu2In, CuIn, In ou CuGa2. Les paramètres contrôlant la composition, la teneur en oxygène, ainsi que la structure des alliages Cu-In-Ga sont déterminés. Le chapitre 4 décrit les traitements thermiques mis au point permettant d'obtenir des absorbeurs compacts de composition souhaitée. La spectroscopie Raman est utilisée pour distinguer les phases : la ségrégation du Ga vers la couche de molybdène est ainsi mise en évidence. Des cellules solaires du type Mo/CIGS/CdS/ZnO sont réalisées, et des rendements de conversion photovoltaïque de 9,8 % sont obtenus, avec présence de phases secondaires appauvries en cuivre dans le matériau.
41
Pettersson, Jonas. "Modelling Band Gap Gradients and Cd-free Buffer Layers in Cu(In,Ga)Se2 Solar Cells". Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-168618.
Testo completoAbstract (sommario):
A deeper understanding of Cu(In,Ga)Se2 (CIGS) solar cells is important for the further improvement of these devices. This thesis is focused on the use of electrical modelling as a tool for pursuing this aim. Finished devices and individual layers are characterized and the acquired data are used as input in the simulations. Band gap gradients are accounted for when modelling the devices. The thesis is divided into two main parts. One part that treats the influence of cadmium free buffer layers, mainly atomic layer deposited (Zn,Mg)O, on devices and another part in which the result of CIGS absorber layer modifications is studied. Recombination analysis indicates that interface recombination is limitting the open circuit voltage (Voc) in cells with ZnO buffer layers. This recombination path becomes less important when magnesium is introduced into the ZnO giving a positive conduction band offset (CBO) towards the CIGS absorber layer. Light induced persistent photoconductivity (PPC) is demonstrated in (Zn,Mg)O thin films. Device modelling shows that the measured PPC, coupled with a high density of acceptors in the buffer-absorber interface region, can explain light induced metastable efficiency improvement in CIGS solar cells with (Zn,Mg)O buffer layers. It is shown that a thin indium rich layer closest to the buffer does not give any significant impact on the performance of devices dominated by recombination in the CIGS layer. In our cells with CdS buffer the diffusion length in the CIGS layer is the main limitting factor. A thinner CIGS layer improves Voc by reducing recombination. However, for thin enough absorber layers Voc deteriorates due to recombination at the back contact. Interface recombination is a problem in thin devices with Zn(O,S) buffer layers. This recombination path is overshadowed in cells of standard thickness by recombination in the CIGS bulk. Thin cells with Zn(O,S) buffer layers have a higher efficiency than CdS cells with the same absorber thickness.
42
Lauth, Jannika [Verfasser], e Horst [Akademischer Betreuer] Weller. "Towards Functional Optoelectronic Nanocrystal Solids : CuIn(Ga)Se2, InxSey and GaAs / Jannika Lauth. Betreuer: Horst Weller". Hamburg : Staats- und Universitätsbibliothek Hamburg, 2014. http://d-nb.info/1048626369/34.
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Lindahl, Johan. "Atomic layer deposition of zinc tin oxide buffer layers for Cu(In,Ga)Se2 solar cells". Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-260882.
Testo completoAbstract (sommario):
The aim of this thesis is to provide an in-depth investigation of zinc tin oxide, Zn1-xSnxOy or ZTO, grown by atomic layer deposition (ALD) as a buffer layer in Cu(In,Ga)Se2 (CIGS) solar cells. The thesis analyzes how changes in the ALD process influence the material properties of ZTO, and how these in turn affect the performance of CIGS solar cells. It is shown that ZTO grows uniformly and conformably on CIGS and that the interface between ZTO and CIGS is sharp with little or no interdiffusion between the layers. The band gap and conduction band energy level of ZTO are dependent both on the [Sn]/([Zn]+[Sn]) composition and on the deposition temperature. The influence by changes in composition is non-trivial, and the highest band gap and conduction band energy level are obtained at a [Sn]/([Zn]+[Sn]) composition of 0.2 at 120 °C. An increase in optical band gap is observed at decreasing deposition temperatures and is associated with quantum confinement effects caused by a decrease in crystallite size. The ability to change the conduction band energy level of ZTO enables the formation of suitable conduction band offsets between ZTO and CIGS with varying Ga-content. It is found that 15 nm thin ZTO buffer layers are sufficient to fabricate CIGS solar cells with conversion efficiencies up to 18.2 %. The JSC is in general 2 mA/cm2 higher, and the VOC 30 mV lower, for cells with the ZTO buffer layer as compared to cells with the traditional CdS buffer layer. In the end comparable efficiencies are obtained for the two different buffer layers. The gain in JSC for the ZTO buffer layer is associated with lower parasitic absorption in the UV-blue region of the solar spectrum and it is shown that the JSC can be increased further by making changes to the other layers in the traditional CdS/i-ZnO/ZnO:Al window layer structure. The ZTO is highly resistive, and it is found that the shunt preventing i-ZnO layer can be omitted, which further increases the JSC. Moreover, an additional increase in JSC is obtained by replacing the sputtered ZnO:Al front contact with In2O3 deposited by ALD. The large gain in JSC for the ZTO/In2O3 window layer stack compensates for the lower VOC related to the ZTO buffer layer, and it is demonstrated that the ZTO/In2O3 window layer structure yields 0.6 % (absolute) higher conversion efficiency than the CdS/i-ZnO/ZnO:Al window layer structure.
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Simsek, Sanli Ekin. "Investigation of Microstructural Defects in Cu(In,Ga)Se2 Thin Films by Scanning Transmission Electron Microscopy". Phd thesis, TUprints, 2019. https://tuprints.ulb.tu-darmstadt.de/8849/1/Simsek_Sanli_Dissertation_2018.pdf.
Testo completoAbstract (sommario):
Polycrystalline Cu(In,Ga)Se2 (CIGS) based thin-film solar cells achieve power-conversion efficiencies of almost 23% on the laboratory scale, one of the highest among thin-film solar cells. The aim of further CIGS research and development is to reach conversion efficiencies of 25%, which is currently the efficiency of the best single-crystalline Si based solar cells. To reach this goal, the factors limiting efficiency, e.g. non-radiative recombination of charge carriers, should be minimized. Such recombination processes may occur at line or planar defects present in the CIGS absorbers (among other interfaces, such as absorber and buffer layer). In the present study, the structure and composition of several defects as well as their evolution during the growth were investigated for an enhanced understanding.
Highest efficiencies in CIGS solar cells are achieved, when the absorber is fabricated with a three-stage co-evaporation process. During the second stage of this process, Cu and Se are evaporated on the initially formed (In,Ga)2Se3 layer. The composition of the absorber becomes Cu-rich ([Cu]/([In] + [Ga]) > 1) during this stage. The change in composition leads to recrystallization, i.e. grain growth and defect annihilation, thus enabling higher conversion efficiencies. Therefore, it is crucial to investigate the recrystallization and the evolution of the microstructure at the second-stage of the CIGS growth. In the literature, two methods were suggested for this purpose: i) investigating the microstructural evolution of diffusion couples during a heating study; ii) ex-situ comparison of a growth-interrupted and a growth-finished sample.
In the first part of this study, a Cu-poor ([Cu]/([In] < 1) CuInSe2 (CIS) precursor layer with a Cu2-xSe capping layer was prepared and heated in a scanning transmission electron microscope (STEM) to mimic the recrystallization. During the Cu diffusion from the Cu-rich Cu2-xSe phase into the Cu-poor CIS phase, the growth of defect-free grains towards the grains with closely-spaced planar defects (PDs) was monitored by low-angle annular dark-field (LAADF) imaging, whereas elemental depth profiles were analyzed by energy-dispersive X-ray spectroscopy (EDXS) before and after heating. The substantial impact of the Cu excess on the recrystallization was also indicated by an in-situ heating experiment of a Cu-poor CIS film without a Cu2-xSe layer on top, in which neither grain growth nor defect annihilation was detected. Monitoring of the recrystallization within the CIS absorber layers was performed for the first time by means of STEM and provided direct evidence for the currently accepted theory of the grain growth mechanism.
In the second part, a CIGS absorber grown via co-evaporation was analyzed. During the growth, one piece of the sample was removed before the recrystallization at the second stage. For the remaining piece, the three-stage process was completed. The defect concentrations as well as the in-depth elemental analysis were performed by STEM-LAADF imaging and EDXS, respectively. Similar to the in-situ heating results, much larger grains with reduced linear/planar defect concentrations were detected in the absorber layer for which the growth had been completed. Although most of the structural defects were annihilated after the recrystallization, few structural defects were detected by LAADF imaging after the recrystallization, and even after the completion of the three-stage growth process.
Further analyses were performed via aberration-corrected, high-resolution STEM (HR-STEM) in combination with electron energy-loss spectroscopy (EELS) to elucidate the nature of individual microstructural defects from various stages of the growth. HR-STEM and EELS results revealed the structure and chemistry of defects that were present in both growth-interrupted and growth-finished samples: Σ3-twin boundaries and stacking faults with stoichiometric elemental distribution; grain boundaries, tilt boundaries and dislocations with cation redistribution, i.e. Cu enrichment and In depletion. Stoichiometric inversion boundaries, Cu enriched ‘complex’ PDs and an extrinsic Frank partial dislocation were detected only in the growth-interrupted Cu-poor samples, whereas a ‘Cu2-xSe secondary phase’ was detected only in the growth-finished absorber layer.
The present work provided direct insight into the recrystallization of CIGS absorbers and evolution of structural defects, as well as a thorough investigation of individual defects in CIGS absorbers.
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Sköld, Markus. "Influence of Na doping on tunnelling rear contact passivation in Cu(In,Ga)Se2 solar cells". Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-311149.
Testo completoAbstract (sommario):
In this thesis Cu(In,Ga)Se2 (CIGS) solar cells with different sodiumdoping of the CIGS absorber and varying Al2O3 rear surface passivationlayer thickness have been manufactured and electrically characterised. Baseline samples and samples without passivation were used asreferences for the passivated samples. For the passivated samplesbetween 1 and 7 nm of Al2O3 were deposited by ALD. The electricalcharacterisation included current-voltage (IV, JV), quantum efficiency (QE, EQE), capacitance-voltage (CV) and temperature dependent currentvoltage (IVT, JVT) measurements. The results show that it is indeed possible to use a tunnel current toconstruct an electrical contact, but that the electrical contact isvery sensitive to sodium doping. The samples with post-depositiontreatment and without Na start to block the tunnel current when thepassivation layer reaches a thickness of about 2 nm, while no blocking of the tunnel current could be observed for the samples with Na pre-deposition. The samples with pre-deposition treatment showed acontinued increase in efficiency all the way to a passivation layerthickness of about 7 nm. When trying to construct samples with eventhicker passivation layer the CIGS started to peel off. For thisreason the optimal thickness for the pre-deposition treated samplescould not be found. The samples with the highest efficiency was thesamples with pre-deposition treatment and thick passivation layer. Those samples showed an increase of 3 percent (absolute) compared tothe unpassivated sample with the same deposition treatment and 1.6 percent higher efficiency compared to the baseline sample. Concluding that tunnelling passivation layer is comparable to the passivationlayer with point contact methods.
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Lundberg, Olle. "Band Gap Profiling and High Speed Deposition of Cu(In,Ga)Se2 for Thin Film Solar Cells". Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3757.
Testo completoAbstract (sommario):
The Cu(In,Ga)Se2-based thin film solar cell is a promising candidate for becoming one of the more important solar cell technologies in the near future. In order to realize such a development a significant reduced production cost of the Cu(In,Ga)Se2 (CIGS) layer is needed. This work shows a possible way towards such a reduction by increasing the deposition rate and decreasing the CIGS thickness with almost maintained device efficiency. Obtaining an improved device performance in CIGS-based solar cells by using an in-depth variation of the band gap has earlier been investigated without any clear conclusions. In this work an extensive experimental study of the beneficial effect of band gap profiling has been performed and firmly based conclusions have been made. For standard CIGS devices the band gap profiling can result in an improved efficiency of around 0.4 % units. This gain is related to improved field-assisted carrier collection. For reduced CIGS thicknesses the importance of a band gap profiling is enhanced, and at a CIGS thickness of 0.5 μm an efficiency gain of 2.5 % units is obtained, resulting in a 13.4 % efficient device. The main reason for the gain is passivation of the back contact, which becomes increasingly detrimental for the device performance as the CIGS thickness is reduced. With an optimized band gap profile the CIGS thickness can be reduced 3-4 times, with almost solely absorption related losses. The potential for increasing the deposition rate of co-evaporated CIGS layers is shown to be large. An increase of up to 10 times compared to commonly used deposition rates is possible with only minor losses in efficiency. By using band gap profiled thin CIGS layers deposited at high rates, the production from a single evaporation system can be increased up 30 times. Such an increase will lead to the needed reduction of the production cost of the complete solar cell module.
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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.
Testo completoAbstract (sommario):
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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Zhang, Zhenhao [Verfasser]. "Nanoscale investigation of potential distribution in operating Cu(In,Ga)Se2 thin-film solar cells / Zhenhao Zhang". Karlsruhe : KIT Scientific Publishing, 2013. http://www.ksp.kit.edu.
Testo completo
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Mönig, Harry [Verfasser]. "Hochenergie-Photoelektronenspektroskopie und winkelabhängige Röntgenemissionsspektroskopie zur tiefenabhängigen Untersuchung von polykristallinen Cu(In,Ga)Se2-Schichten / Harry Mönig". Berlin : Freie Universität Berlin, 2009. http://d-nb.info/1027498302/34.
Testo completo
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Hsu, Hwai Ren, e 徐懷仁. "Epitaxy Growth Cu(In,Ga)Se2 Heterojunction structrue". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/56112362527071510829.
Testo completo