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Pérez, Boix Pablo. „Organic Photovoltaics: cell processing, device physics and electrical characterization“. Doctoral thesis, Universitat Jaume I, 2012. http://hdl.handle.net/10803/669172.
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Esta tesis tiene como objetivo el estudio de las células solares basadas en materiales orgánicos, lo que nos permitirá tanto acceder a un conocimiento exhaustivo de sus mecanismos de operación como señalar posibles mejoras para el funcionamiento de estos dispositivos. Para ello exploraremos su procesado, la caracterización eléctrica y, especialmente, el modelaje físico de las células de heterounión masiva. La capa activa de éstas está formada por una mezcla de material donador (normalmente un polímero como el P3HT i el PPV) que recolecta la luz, y material aceptor (de forma habitual un derivado del fullereno); siendo en la interface de estos dos materiales se produce la separación de cargas que origina el fotón absorbido. Con electrón y hueco en medios distintos, podemos extraerlos transportándolos hasta sus respectivos contactos. Para entender que provoca estos procesos partimos del confinamiento del campo eléctrico debido al dopaje. Existen distintas evidencias que apuntan a que el polímero que forma la capa activa tiene, debido a la humedad, oxígeno y defectos estructurales derivados del procesado, un dopaje que forma una zona de carga descubierta. Con esto la recombinación se convierte en el mecanismo principal de pérdida energética, determinando la curva de corriente-voltaje, fill factor y, junto a la distribución de estados del material aceptor, el potencial a circuito abierto.
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Yandt, Mark. „Characterization and Performance Analysis of High Efficiency Solar Cells and Concentrating Photovoltaic Systems“. Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20535.
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As part of the SUNRISE project (Semiconductors Using Nanostructures for Record Increases in Solar-cell Efficiency), high efficiency, III-V semiconductor, quantum-dot-enhanced, triple-junction solar cells designed and manufactured by Cyrium Technologies Inc. were integrated into OPEL Solar, MK-I, Fresnel-lens-based, 550x concentrating modules carried on a dual axis tracker.
Over its first year of operation 1.8 MWh of AC electrical energy was exported to the grid. Measurements of the direct and indirect components of the insolation, as well as the spectral irradiance of light incident on the demonstrator in Ottawa, Canada are presented. The system efficiency is measured and compared to that predicted by a system model to identify loss mechanisms so that they can be minimized in future deployments.
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Taylor, Paul Alan. „Proton radiation effects on space solar cell structures and materials“. Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242506.
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Kang, Moon Hee. „Development of high-efficiency silicon solar cells and modeling the impact of system parameters on levelized cost of electricity“. Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47647.
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The objective of this thesis is to develop low-cost high-efficiency crystalline silicon solar cells which are at the right intersection of cost and performance to make photovoltaics (PV) affordable. The goal was addressed by improving the optical and electrical performance of silicon solar cells through process optimization, device modeling, clever cell design, fundamental understanding, and minimization of loss mechanisms. To define the right intersection of cost and performance, analytical models to assess the premium or value associated with efficiency, temperature coefficient, balance of system cost, and solar insolation were developed and detailed cost analysis was performed to quantify the impact of key system and financial parameters in the levelized cost of electricity from PV.
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Weber, Oliver. „Structural chemistry of hybrid halide perovskites for thin film photovoltaics“. Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.761012.
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Hybrid lead halide perovskites, AMX 3 compounds in which A = CH 3 NH 3 (MA), CH(NH 2 ) 2(FA), Cs; M = Pb,Sn; X = I, Br, Cl, display remarkable performance in solution-processed optoelectronic devices, including > 22% efficient thin film photovoltaic cells. These compounds represent the first class of materials discovered to exhibit properties associated with high performance compound semiconductors, while being formed at or near room temperature using simple solution chemistry techniques. This thesis is focused on the synthesis, structural characterisation and phase behaviour of MAPbI 3 , FAPbI 3 , A-site solid solutions and novel organic metal halide framework materials. The complete atomic structure and phase behaviour of methylammonium lead iodide is elucidated for the first time, including hydrogen positions, using high flux, constant wave-length neutron powder diffraction. At 100 K an orthorhombic phase, space group Pnma, is observed, with the methylammonium cations ordered as the C–N bond direction alternates in adjacent inorganic cages. Above 165 K a first order phase transition to tetragonal, I4/mcm, occurs with the unlocking of cation rotation, which is disordered primarily in the ab plane. Above 327 K a cubic phase, space group Pm3m, is formed, with the cations isotropically disordered on the timescale of the crystallographic experiment. The high temperature phase of formamidinium lead iodide, α-FAPbI 3 is shown for the first time to be cubic, (Pm3m), at room temperature using time-of-flight, high resolution neutron powder diffraction. Polymorphism and the low temperature phase behaviour of FAPbI 3 have been further investigated using reactor and spallation neutron sources with high resolution in temperature. A tetragonal phase, P4/mbm, is confirmed in the temperature range 140-285 K.The composition, structural and optical parameters of ’A’ site solid solutions (MA/FA)PbI 3 have been investigated by single crystal X-ray diffraction, UV-vis spectroscopy and 1 H solution NMR. A composition-dependent transition in the crystal class from tetragonal to cubic(or pseudo-cubic) at room temperature is identified and correlated to trends in the optical absorption. Novel hybrid materials with inorganic frameworks of varying dimensionality from 0D to 2D, including imidazolium lead iodide and piperazinium lead iodide, have been synthesised using various templating organic cations and their atomic structures solved by single crystal X-ray diffraction.
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Park, Yoonseok. „Light trapping substrates and electrodes for flexible organic photovoltaics“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-219686.
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Organic solar cells are one of the most promising candidates for future solar power generation. They are thin and lightweight with several additional advantages such as scalability, environmental sustainability and low cost for processing and installation. However, the low charge carrier mobility of the absorbing material for organic solar cells requires thin absorber layers, limiting photon harvesting and the overall power conversion efficiency. Several attempts, e.g., periodically patterned structures and scattering layers have been tried to enhance the absorption of thin-film solar cells as light trapping elements. However, much effort is required to introduce light trapping structures to conventional rigid metal oxide electrodes and glass substrate. For instance, almost 13 hours are required to fabricate micro structures of 1 m2 area on glass, in contrast, 1 minute on PET using a same laser set-up and an additional scattering layers are demanded for providing light trapping effects to solar cells. In the last years, flexibility is emerging as the one of the major advantages of organic solar cells. To realize flexibility of solar cells, the classically used glass substrates and ITO electrodes are too brittle. Therefore, polymer materials are promising candidates to replace them as flexible electrodes and substrates. In this thesis, the highly transparent conducting polymer, PEDOT:PSS and PET equipped with an AlOx encapsulation layer are used as electrode and substrate, respectively. Besides the flexibility, additional light trapping elements, e.g. scattering particles, nano- and microstructures can be easily applied to the polymer materials since they have the potential for easier shaping and processing. In this study, we apply different light trapping and in-coupling approaches to organic solar cells. First, PET substrates are structured with a direct laser interference patterning system, which is a powerful and scalable one-step technique for patterning polymers. Almost 80 % of the light is diffracted by these patterned PET substrates and thereby the light path in the absorption layer is increased. Optical display films, commercially developed to be used as back light units of liquid crystal displays are also examined as light trapping substrates and exhibit similar enhancement as patterned PET. Moreover, since PEDOT:PSS is prepared by a solution-based process, TiO2 nanoparticles are added as light scattering elements to the PEDOT:PSS electrodes. Consequently, those electrodes provide a dual function as electrical contact and light trapping element. Finally, 2- or 3-dimensional nanostructures are printed by a nano-imprinting technique onto the surface of PEDOT:PSS with PDMS stamps. By controlling the temperature and the time of PEDOT:PSS during an annealing step, nanostructures are transferred from PDMS masks to PEDOT:PSS. To evaluate the effects of light trapping for all above mentioned approaches, flexible organic solar cells are produced by vacuum evaporation using blends of DCV5T-Me and C60 as absorber layer. The substrates are optically characterized using UV-vis spectrometer and goniometer measurements. The topography of the samples is measured by atomic force microscopy, scanning microscopy and optical microscopy. Bending tests with various radii are performed to test the flexibility of the substrates. In summary, light trapping effects are successfully implemented in the electrodes and substrates for OPVs, giving efficiency improvements of up to 16 %. The light trapping mechanisms in our approaches are extensively discussed in this thesisOrganische Photovoltaik ist einer der vielversprechendsten Kandidaten für die zukünftige Solarstromgewinnung auf flexiblen Substraten. Um diese Flexibilität zu ermöglichen, sind herkömliche Glassubstrate mit ITO-Elektroden zu spröde. Ein vielversprechender Kandidat, um sowohl flexible Elektroden als auch flexible Substrate herzustellen, sind Polymere, da diese sehr biegsam und leicht zu verarbeiten sind. Deshalb wird in dieser Arbeit das hoch transparente, leitfähige Polymer PEDOT:PSS als Elektrode und PET (mit einer AlOx Verkapselungsschicht) als Substrat untersucht. Aufgrund der guten Prozessierbarkeit der Polymere konnten wir zusätzlich zu den eigentlichen Funktionen des Substrates und der Elektrode noch den Mechanismus des Lichteinfangs hinzufügen. Zusätzlich zu ihrer Flexibilität haben organische Solarzellen noch weitere Vorteile: sie sind dünn, leicht, skalierbar und verursachen vergleichsweise geringe Kosten für Herstellung und Installation. Ein Nachteil organischer Solarzellen ist die vergleichsweise geringe Ladungsträgerbeweglichkeit der Absorbermaterialien, welche oft die Schichtdicke der Absorbermaterialien begrenzt. Dies hat weniger absorbierte Photonen, weniger Stromdichte und somit einen geringeren Wirkungsgrad zur Folge. In den letzten Jahren wurden periodisch strukturierte Substrate und streuende Schichten als Lichteinfangelemente eingesetzt, um den Wirkungsgrad organischer Solarzellen mit dünnen Absorberschichten zu erhöhen. Gestaltungsregeln für solche Lichteinfangelemente sind noch weitestgehend unbekannt. Im Rahmen dieser Arbeit strukturieren wir PET Substrate mit einem direkten Laserinterferenzsystem, welches ein leistungsfähiges, skalierbares Einschrittverfahren zur Polymerstrukturierung ist. Da PEDOT:PSS aus der Lösung prozessiert wird, können wir weiterhin Nanopartikel hinzufügen, die der Elektrode zusätzlich noch lichtstreuende Eigenschaften geben. Außerdem können 2- bzw. 3-dimensionale Nanostrukturen leicht mithilfe einer Stempeltechnik eingeprägt werden. Um die Effekte des Lichteinfangs, welcher durch die oben genannten Methoden erzeugt wird, zu untersuchen, werden flexible organische Solarzellen mittels Vakuumverdampfung prozessiert. DCV5T-Me und C60 bilden dabei die photoaktive Schicht. Somit werden die Licht fangenden Eigenschaften dieser flexiblen Solarzellen ausgenutzt und ausführlich in der Arbeit diskutiert
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Aronsson, Oscar, Daniel Nyqvist und Simon Robertsson. „Solar energy production at Heby Skola : A pilot study of a photovoltaic installation in Sweden“. Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-201894.
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Photovoltaic is a renewable energy technology that creates electricity by converting the energy of light. Photovoltaics are usually installed on buildings. In this pilot study, the viability of such an installation on the roof of the school Heby skola is examined with respect to produced electricity, economic potential and environmental impact. This is done with the software Solelekonomi, together with 11-years of solar irradiance data and measurements of the properties of the intended roof, which made it was possible to simulate the production patterns of a photovoltaic system. The simulations were made on two possible system sizes 50 m2 and 200 m2 with respectively 7.75 and 31 kWpeak installed power. Among other things, the results showed that 1.1% and 4.45% of the total electricity consumption could be replaced by the systems. A PV investment was found to be a good option with respect to the sections examined. Furthermore, considering PVinstallations, the school was found to be representative for schools in Sweden, and thus this essay can provide a basis for other PV pilot project on Swedish schools.
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Lee, Jae-Hyeong. „Studies on Coating Process for Organic/Inorganic Thin-Films for Photovoltaics“. Kyoto University, 2014. http://hdl.handle.net/2433/188819.
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Lee, Michael M. „Organic-inorganic hybrid photovoltaics based on organometal halide perovskites“. Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:9384fc54-30de-4f0d-86fc-71c22d350102.
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This thesis details the development of a novel photovoltaic device based on organometal halide perovskites. The initial focus of this thesis begins with the study of lighttrapping strategies in solid-state dye-sensitised solar cells (detailed in chapter 3). While I report enhancement in device performance through the application of near and far-field light-trapping techniques, I find that improvements remain step-wise due to fundamental limitations currently employed in dye-sensitised solar cell technology— notably, the available light-sensitising materials. I found a promising yet under researched family of materials in the methyl ammonium tri-halide plumbate perovskite (detailed in chapter 4). The perovskite light-sensitiser was applied to the traditional mesoscopic sensitised solar cell device architecture as a replacement to conventional dye yielding world-record breaking photo-conversion e!ciencies for solid-state sensitised solar cells as high as 8.5%. The system was further developed leading to the conception of a novel device architecture, termed the mesoporous superstructured solar cell (MSSC), this new architecture replaces the conventional mesoporous titanium dioxide semiconductor with a porous insulating oxide in aluminium oxide, resulting in very low fundamental losses evidenced through high photo-generated open-circuit voltages of over 1.1 V. This development has delivered striking photo-conversion ef- ficiencies of 10.9% (detailed in chapter 6).
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Patrick, Christopher Edward. „Photoemission spectra of nanostructured solar cell interfaces from first principles“. Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:fa2333ea-7016-4d6f-8d55-aee4178482a6.
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Photovoltaic (PV) technologies could provide abundant, clean and secure energy through the conversion of sunlight into electricity, but currently are too expensive to compete with conventional sources of power. Novel PV devices incorporating nanostructured materials, such as the dye-sensitized solar cell (DSC), have been identified as viable, low-cost alternatives to traditional solar cell designs. In spite of technological progress in the field over the last twenty years, the underlying physics governing DSC operation is still not well understood. In this thesis, first-principles (i.e. parameter-free) calculations are performed with the aim of connecting experimentally-measured photoemission data to the underlying atomistic and electronic structure of interfaces found in DSCs. The principal system under study is the interface between anatase titanium dioxide (TiO2) and the "N3" dye molecule, one of the most widely-investigated device designs in DSC research. Atomistic models of the interface are determined within density-functional theory. Core-level spectra of these interface models are then calculated using a ∆SCF approach. Comparison of the calculations to published experimental data finds that intermolecular interactions have a significant effect on the spectra. Next, the electronic structure of bulk TiO2 and of isolated N3 molecules is calculated using the GW approximation and ∆SCF method respectively. For the former, it is shown that including Hubbard U corrections in the initial Hamiltonian reduces the GW gap by 0.4 eV. These calculations are then used to determine the valence photoemission spectrum of the full interface. By including image-charge effects, thermal broadening and configurational disorder, quantitative agreement with experimentally-measured spectra is demonstrated. In addition to the N3/TiO2 system, calculations of the core-level spectra of the interfaces between TiO2 and H2O and bi-isonicotinic acid are also presented. The thesis concludes with a study of the X2Y3/TiO2 interfaces (X=Sb, Bi; Y=S, Se) found in recently-developed semiconductor-sensitized solar cells.
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Magubane, Siphesihle Siphamandla. „Metal assisted chemically etched silicon nanowires for application in a hybrid solar cell“. University of the Western Cape, 2018. http://hdl.handle.net/11394/6733.
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>Magister Scientiae - MScPhotovoltaic (PV) devices based on inorganic-organic hybrid active layers have been extensively studied for over a decade now. However, photoactive hybrid layers of material combinations such as rr-P3HT and SiNWs still require further exploration as candidates for solar cell (SC) fabrication, due to favourable optical absorption and charge carrier mobility associated with them respectively. The ultimate goal of the study is to fabricate ITO/PEDOT:PSS/rr-P3HT:SiNWs/Al SCs with different SiNWs content and investigate the different parameters or factors influencing the performance of these cells. The vertically aligned SiNW arrays on a Si wafer were synthesised via metal assisted chemical etching (MACE) and a method of chemically detaching these wires was developed. The average length and the diameter of the SiNWs obtained were 4.5 μm and 0.2 μm, respectively. Different weight ratios of as-synthesised SiNWs were then incorporated within rr-P3HT to form different hybrid solutions, i.e. rr-P3HT: 0.3 wt% SiNWs, rr-P3HT: 0.7 wt% SiNWs and rr-P3HT: 1.3 wt% SiNWs. In addition, a pure rr- P3HT solution was made for reference purposes. SEM characterisation shows that the SiNWs are randomly distributed across the active area, and that the film becomes progressively inhomogeneous upon addition of SiNWs, whereas the TEM characterisation revealed that there is no chemical interaction between the rr-P3HT and SiNWs. The UV-Vis and PL spectra suggest that there are changes in absorption and emission characteristics upon SiNW incorporation into the rr-P3HT matrix, which may have impacted the charge transfer .The electrical properties of the different hybrid films were probed using Hall Effect measurements, which revealed that the conductivity increases with the increase in the concentration of nanowires (NWs). The increase in conductivity upon the addition of SiNWs in the rr-P3HT matrix was related to an increase of the mobility (μ) of charge carriers in the hybrid films.
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Pachoumi, Olympia. „Metal oxide/organic interface investigations for photovoltaic devices“. Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/246263.
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This thesis outlines investigations of metal oxide/organic interfaces in photo-voltaic devices. It focuses on device instabilities originating from the metal oxide layer surface sensitivity and it presents suggested mechanisms behind these in- stabilities. A simple sol-gel solution deposition technique for the fabrication of stable and highly performing transparent conducting mixed metal oxides (ZnMO) is presented. It is demonstrated that the use of amorphous, mixed metal oxides allows improving the performance and stability of interfacial charge extraction layers for organic solar cells. Two novel ternary metal oxides, zinc-strontrium- oxide (ZnSrO) and zinc-barium-oxide (ZnBaO), were fabricated and their use as electron extraction layers in inverted organic photovoltaics is investigated. We show that using these ternary oxides can lead to superior devices by: prevent- ing a dipole forming between the oxide and the active organic layer in a model ZnMO/P3HT:PCBM OPV as well as lead to improved surface coverage by a self assembled monolayer and promote a significantly improved charge separation efficiency in a ZnMO/P3HT hybrid device. Additionally a spectroscopic technique allowing a versatility of characterisa- tion for long-term stability investigations of organic solar cells is reported. A device instability under broadband light exposure in vacuum conditions for an inverted ZnSrO/PTB7:PC71BM OPV is observed. Direct spectroscopic evidence and electrical characterisation indicate the formation of the PC71BM radical an- ion associated with a loss in device performance. A charge transfer mechanism between a heavily doped oxide layer and the organic layers is suggested and dis- cussed.
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Anselmo, Ana Sofia. „Materials aspects in spin-coated films for polymer photovoltaics“. Doctoral thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-16107.
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Polymer-based photovoltaics have the potential to contribute to boosting photovoltaic energy conversion overall. Besides allowing large-area inexpensive processing, polymeric materials have the added benefit of opening new market applications for photovoltaics due to their low-weight and interesting mechanical properties. The energy conversion efficiency values of polymer photovoltaics have reached new record values over the past years. It is however crucial that stability issues are addressed together with efficiency optimization. Understanding fundamental materials aspects is key in both areas. In the work presented in this thesis, the morphology of polymer:fullerene films and its influence on device performance was studied, as well as the effect of light exposure on the surface of fullerene films. Several polyfluorene copolymers were used for the morphology studies, where the effects of changing spin-coating solvent and of side chain engineering were investigated with dynamic secondary ion mass spectrometry (dSIMS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Polymer-enriched surfaces were found in all blend films, even in the cases with homogeneous distributions in the bulk. Side chain engineering of the polymer led to gradual changes in the compositional variations perpendicular to the surface, and to slight variations in the photocurrent. The electronic structure of the fullerene derivative PCBM was studied in detail and the spectroscopic fingerprint of the materials was analysed by comparison with theoretically simulated spectra. Photo-stability studies done in air showed that the surface of fullerene films underwent severe damages at the molecular level, which is evident from changes in the valence band and X-ray absorption spectra. These changes were explained by transitions from sp2-type to sp3 hybridization of the carbon atoms in the cage that resulted in the destruction of the fullerene cage.
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Tan, Xinxuan. „Applications of Multichannel Spectroscopic Ellipsometry for CdTe Photovoltaics: From Window Layers to Back Contacts“. University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1513371404463035.
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Avachat, Upendra Sureshchandra. „DEVELOPMENT OF TRANSPARENT AND CONDUCTING BACK CONTACTS ON CdS/CdTe SOLAR CELLS FOR PHOTOELECTROCHEMICAL APPLICATION“. Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2889.
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The development of devices with high efficiencies can only be attained by tandem structures which are important to the advancement of thin-film photoelectrochemical (PEC) and photovoltaic (PV) technologies. FSEC PV Materials Lab has developed a PEC cell using multiple bandgap tandem of thin film PV cells and a photocatalyst for hydrogen production by water splitting. CdS/CdTe solar cell, a promising candidate for low-cost, thin-film PV cell is used as one of the thin film solar cells in a PEC cell. This research work focuses on developing various back contacts with good transparency in the infrared region (~750 - 1150 nm) for a CdS/CdTe solar cell. CdS/CdTe solar cells were prepared with three different configurations, Glass/SnO2:F/CdS/CdTe/ZnTe:Cu/ITO/Ni-Al (series 1), Glass/SnO2:F/CdS/CdTe/Cu2Te/ITO/Ni-Al (series 2), Glass/SnO2:F/CdS/CdTe/Br-Me etching/Cu/ITO/Ni-Al (series 3). The back contact preparation process for a CdS/CdTe solar cell involves the deposition of a primary p-type back contact interface layer followed by the deposition of transparent and conducting ITO and a Ni-Al outer metallization layer. Back contact interface layers were initially optimized on glass substrates. A ZnTe:Cu layer for a series 1 cell was deposited using hot wall vacuum evaporation (HWVE). Cu2Te and Cu thin films for series 2 and series 3 cells were deposited by vacuum evaporation. HWVE technique produced highly stoichiometric ZnTe:Cu thin films with cubic phase having {111} texture orientation. All the back contact interface layers demonstrated better transparency in the infrared region on glass substrate. Formation of crystalline phase and texture orientation were studied using X-ray diffraction (XRD). The composition was analyzed by electron probe microanalysis (EPMA). Transparency measurements were carried out by optical transmission spectroscopy. Thickness measurements were carried out using a DEKTAK surface profile measuring system. Finally, completed solar cells for all the series were characterized for current-voltage (I-V) measurements using the I-V measurement setup developed at the FSEC PV Materials Lab. The PV parameters for the best series 1 cell measured at an irradiance of 1000 W/m2 were: open circuit voltage, Voc = 630 mV, short circuit current, Isc = 7.68 mA/ cm2, fill factor, FF = 37.91 %, efficiency, ç = 3.06 %. The PV parameters for the best series 2 cell measured were: Voc = 690 mV, Isc = 8.7 mA/ cm2, FF = 45.19 %, ç = 4.8 %. The PV parameters for the best series 3 cell measured were: Voc = 550 mV, Isc = 9.70 mA/ cm2, FF = 42.25 %, ç = 5.63 %. The loss in efficiency was attributed to the possible formation of a non-ohmic contact at the interface of CdTe and back contact interface layer. Decrease in the fill factor was attributed to high series resistance in the device.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
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Uhrich, Christian. „Strategien zur Optimierung organischer Solarzellen: Dotierte Transportschichten und neuartige Oligothiophene mit reduzierter Bandlücke“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1209113927393-76737.
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Organische Solarzellen besitzen das Potential für leichte und zugleich flexible photovoltaische Anwendungen, die kostengünstig hergestellt werden können und damit einen Beitrag zur Verminderung der Emission von Kohlendioxid, Methan und Stickoxiden leisten können. Zur Herstellung von organischen Solarzellen werden nur geringe Mengen der organischen Materialien benötigt und die Prozessierung findet bei vergleichsweise geringen Temperaturen statt, was die Abscheidung auf z. B. Plastikfolie ermöglicht. Man unterscheidet drei Arten von organischen Solarzellen. Erstens, Solarzellen bestehend aus kleinen Molekülen, die im Vakuum durch Sublimation auf das Substrat abgeschieden werden. Zweitens, Polymersolarzellen, deren Schichten aus Lösung meist durch „spin-coating“ oder Druckverfahren präpariert werden. Und drittens, „dye-sensitized“ Solarzellen (auch Grätzel-Zellen), die aus einer porösen Schicht Titandioxid und einem flüssigen Elektrolyten für den Ladungsträgertransport bestehen. Diese Arbeit beschäftigt sich ausschließlich mit organischen Solarzellen aus kleinen Molekülen. Die höchsten erreichten Wirkungsgrade organischer Solarzellen aus kleinen Molekülen liegen derzeit bei etwa 5 % . Um die Effizienzen von Solarzellen aus kleinen Molekülen zu steigern, ist es einerseits notwendig das Verständnis der physikalischen und chemischen Prozesse innerhalb der Bauelemente genauer beschreiben zu können, andererseits werden neue Materialien mit optimierten Eigenschaften für die organische Photovoltaik benötigt. In dieser Arbeit wurden zwei Strategien zur Optimierung organischer Solarzellen verfolgt: • Durch die Optimierung des Versatzes der Energieniveaus der organischen Materialien konnte die Leerlaufspannung in einem Modellsystem maximiert werden. An diesem Modellsystem wurden der Ursprung der Leerlaufspannung und die Rekombinationsdynamik von photogenerierten Ladungsträgern untersucht. Bezüglich der Leerlaufspannung zeigen Solarzellen, deren photoaktive Materialien in einer Mischschicht vorliegen, im Vergleich zu Solarzellen, die eine photoaktive Doppelschicht beinhalten, fundamentale Unterschiede . • Des Weiteren wurden neue Thiophenderivate untersucht, die als aktive Materialien in organischen Solarzellen eingesetzt wurden. Durch elektronenziehende Endgruppen wurde das Ionisationspotential der Thiophenderivate abgesenkt und die optische Bandlücke verringert. Das Thiophenderivat DCV3T fungiert in Kombination mit herkömmlichen Donator-Materialien als Akzeptor. In Mischschichten aus DCV3T und C60 kommt es durch einen Hin- und Rücktransfer der Anregungsenergie zwischen den Materialien statt der Generation von freien Ladungsträgern zu einer Erhöhung der Triplett-Exzitonendichte auf DCV3T . Diese Exzitonen besitzen auf Grund der hohen Lebensdauer von Triplett-Exzitonen das Potential für eine erhöhte Exzitonendiffusionslänge, die in einem neuen Solarzellenkonzept ausgenutzt werden konnteOrganic solar cells have the potential for light weight and flexible applications. They can be manufactured cost-effectively and can thus contribute to the reduction of the emission of carbon dioxide, methane and nitric oxides. In order to manufacture organic solar cells, only small amounts of organic materials are required. They can be processed at comparably low temperatures. Therefore, the fabrication on substrates like plastic foil is possible. Three different types of organic solar cells exist. The first kinds are solar cells prepared from small molecules that are manufactured via sublimation of the material in a vacuum. The second kind are polymer solar cells manufactured from solution by spin coating techniques or ink jet printing. And thirdly, dye sensitized solar cells - also known as Grätzel cells - consisting of a porous layer of titanium dioxide and most commonly a liquid electrolyte for the charge transport. This work deals exclusively with small molecule solar cells. The highest power conversion efficiencies reached by small molecule organic photovoltaics are now in the range of 5 %. In order to increase the efficiencies of solar cells prepared from small molecules, two major aspects must be developed. The understanding of the physical processes within the organic devices must be improved. And secondly, new materials are required with physical properties optimized for organic photovoltaics. In this work, I followed two strategies for optimizing organic solar cells: • By optimizing the offset of energy levels between donor and acceptor material, the open circuit voltage could be increased. In the investigated model system, the origin of the open circuit voltage and the recombination dynamics of photo generated charge carriers were analyzed. Concerning the open circuit voltage, solar cells consisting of a donor acceptor double layer structure, show fundamental differences to solar cells consisting of a donor acceptor blend. • Furthermore, new thiophene derivatives used as photoactive materials were investigated. By the attachment of electron withdrawing end groups, the ionization potential of the oligothiophenes is increased and the optical band gap is reduced at the same time. The investigated thiophene derivative DCV3T acts as an acceptor in combination with the commonly used donor-materials. A back- and forth-transfer of excitation energy is observed in blends of DCV3T and fullerene C60. In these blends, excitons are not separated into free charge carriers. This back and forth transfer leads to an enhancement of the density of triplet excitons on DCV3T. These excitons have a potentially high diffusion length due to the long lifetime of triplet excitons. This effect was utilized in the organic solar cells
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Ruankham, Pipat. „Studies on Morphological Effects and Surface Modification of Nanostructured Zinc Oxide for Hybrid Organic/Inorganic Photovoltaics“. Kyoto University, 2014. http://hdl.handle.net/2433/188820.
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Robertson, Kyle. „Optoelectronic Device Modeling of GaAs Nanowire Solar Cells“. Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39710.
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Nanowire solar cells have great potential as candidates for high efficiency, next-generation solar cell devices. To realize their potential, accurate and efficient modeling techniques en- compassing both optical and electrical phenomena must be developed. In this work, a coupled optical and electronic model of GaAs nanowire solar cells was developed, with the goal of building a platform for automated, algorithmic device optimization.
Significant work was done on the optical portion of model, with the goal of reducing run- times and improving the level of automation. Enhancements were made to an open-source implementation of the Rigorous Coupled Wave Analysis method for solving Maxwell’s equations, to make it more accurate for modeling nanowire solar cells. Its accuracy and efficiency were thoroughly investigated, and with the enhancements presented here it was shown to be an effective technique for rapid optical modeling of nanowire devices. Purely optical optimizations of a sample AlInP-passivated GaAs nanowire on a GaAs substrate were performed to demonstrate the efficacy of the technique using a Nelder-Mead simplex optimization of device geometry.
The optical model was then coupled into a finite volume method based electrical model implemented in TCAD Sentaurus, to compute device efficiencies and ultimately optimize electrical device performance. As a first step, an algorithmic optimization of a p-i-n nanowire solar cell consisting of an AlInP-passivated GaAs nanowire on a Si substrate was performed using the generation rates computed by the enhanced RCWA implementation. The overall geometry was fixed to the result of the optical optimization, and only internal electrical parameters were optimized. The results showed that significant performance improvements can be obtained with the right choice of doping levels and doping region configurations, even without optimizing the global device geometry.
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Flimel, Karol. „Využití nanomateriálů pro organickou elektroniku a fotovoltaiku“. Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2011. http://www.nusl.cz/ntk/nusl-216677.
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The study of the new materials potentially usable for organic photovoltaic and electronics are getting very important from the point of ecological and financial view. Organic electronic devices are getting more and more popular and it is only up to us to search for the new ones that are able to improve their physical properties. The aim of this thesis is to search for materials like have been mentioned above which have very good semiconducting properties. Solutions of pure materials and its mixtures with different concentrations of fullerene have been investigated by ultra-violet spectroscopy, classical fluorescence and time resolved spectrometry. Mainly, were studied the influence of the central atom and side substituents for the optical and electronical properties of our materials of interest. With adding fullerene was observed quenching phenomena of the fluorescence, because all these new materials show usually high photoluminescence. Based on the given results, the most suitable materials had been chosen to provide trial of making organic solar cell, and therefore investigated by the mean of electric measurements (direct current).
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Sankaranarayanan, Harish. „Fabrication of CIGS absorber layers using a two-step process for thin film solar cell applications“. [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000366.
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Bhandari, Khagendra P. „Characterization and Application of Colloidal Nanocrystalline Materials for Advanced Photovoltaics“. University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1430327894.
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Nemitz, Ian R. „Synthesis of Nanoscale Semiconductor Heterostructures for Photovoltaic Applications“. Bowling Green State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1277087935.
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Marčík, Silvestr. „Detekce defektů solárních článků pomocí systému využívajcího elektroluminiscenci“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-318496.
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The master thesis focuses primarily on issues of photovoltaic cells in terms of their defects. The introductory part deals with the history of photovoltaics, their introduction into practice and finally an explanation of the photoelectric effect itself. The thesis also describes photovoltaic cells themselves. It explains their principle, advantages, disadvantages and the creation of photovoltaic systems. A substantial part of the work is focused on the topic of detection of defects using luminescent methods. Subsequently, it describes procedural defects arising from the improper handling of already manufactured products. The final part deals with the main topic of the work, which is a detection using luminescence methods and it also mentions the non-luminescence method LBIC. The practical part of the master thesis contains the analysis of the current solution and of the subsequent proposal of solution using a low cost camera. It describes how to modify the camera, verify its spectral sensitivity using a spectrometer and measure the sensitivity of the CMOS sensor. The conclusion is focused on verifying the functionality of the proposed solution on different sources of infrared radiation and photovoltaic panels themselves.
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Kim, Vincent Oteyi. „Ultrafast spectroscopy of organic semiconductors : singlet fission and nonfullerene acceptors for organic photovoltaics“. Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/283561.
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In this dissertation, we investigate two emerging strategies for enhancing the performance of organic photovoltaics. The first takes advantage of a process called singlet exciton fission, and the second embodies an exodus from the fullerene electron acceptors prominent in organic solar cells. Indeed, this versatile class of tunable small molecules are aptly termed nonfullerene acceptors. However, both strategies would benefit from a greater understanding of underlying principles. Singlet exciton fission is a photon-multiplying process in which a singlet exciton from a high-energy absorbed photon splits into two triplet excitons. The process could significantly reduce energy lost to heat in photovoltaic devices, but its mechanisms are still misunderstood. One model involves direct coupling between the singlet and triplet states, and another model involves an intermediate charge transfer state. Transient absorption spectroscopy allowed us to examine singlet fission in films of pentacene, fluorinated pentacene, and coevaporated blends of various mixing ratios. We directly observe an intermolecular charge transfer state during singlet fission in solid films of coevaporated pentacene and peruoropentacene, which supports the model of charge transfer state-mediated singlet fission. Furthermore, we successfully induced singlet fission in one blend by directly exciting the charge transfer state below the bandgap. We use various types of steady state and time-resolved spectroscopy to characterize two types of nonfullerene electron acceptors. The first type is a group of tetraazabenzodiuoranthene diimide (BFI) dimers and a BFI monomer. The BFI dimers were designed to have twisted, nonplanar 3-dimensional structures and have helped achieve power conversion efficiencies of over 8% in organic solar cells. The other type of nonfullerene acceptor is a calamitic small molecule, and we consider the BAF-4CN electron acceptor, which has also been used in a solar cell whose efficiency exceeded 8%. Spectroscopic studies give insight into the performances of these nonfullerene devices in relation to fullerene-derivative counterparts. We find that the nonfullerene blends suffer from more geminate charge recombination. However, despite this drawback, in some cases, slower rates of nongeminate recombination may lead to successful power conversion efficiencies in nonfullerene solar cells.
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Sreng, Mengkoing. „Development of in-situ photoluminescence characterization tools for the study of semiconductors for photovoltaics application“. Thesis, Institut polytechnique de Paris, 2019. http://www.theses.fr/2019IPPAX003.
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Au cours des dernières décennies, le rendement des cellules photovoltaïques a été considérablement amélioré, atteignant presque la limite théorique de Shockley-Queisser. À ce stade, une compréhension profonde des propriétés des matériaux et de leur évolution au cours des processus de fabrication des cellules solaires devient de plus en plus cruciale pour améliorer encore le rendement de la conversion des cellules. Pour cette raison, ma thèse a été axée sur le développement des outils de caractérisation in-situ, qui permettent d'étudier les propriétés des matériaux en temps réel pendant les processus. Les outils ont été développés sur la base de techniques de photoluminescence, dans lesquelles l'échantillon (matériaux semi-conducteurs) est optiquement excité et émet simultanément des photons avec une énergie approximativement égale à la bande interdite des matériaux. Dans cette thèse, trois outils de caractérisation in situ seront présentés.La SSPL in-situ, basée sur la technique de photoluminescence à l'état d'équilibre, est développée pour étudier les propriétés des matériaux semi-conducteurs au cours des processus en mesurant directement l'intensité du signal PL. Après la mise à niveau du système d'acquisition optique, l'outil a été utilisé pour étudier l'évolution des propriétés de surface de silicium cristallin, passivée par l'oxyde d'aluminium (Al2O3) développé par ALD et de silicium amorphe hydrogéné (a-Si:H) développé par PECVD, sous exposition au plasma Ar/H2 dans différentes conditions. À partir de ces expériences, les différences comportement entre l’échantillon passivé par Al2O3 et l’échantillon passivé par a-Si:H ont été observées et discutées. De plus, grâce à l'expérience d'exposition au plasma à travers une fenêtre optique (MgF2), la cause de la dégradation de la passivation de surface induite par le plasma était déterminée. Enfin et surtout, la relation entre la dynamique de la dégradation induite par le plasma et les paramètres du plasma (par exemple, puissance RF appliquée, pression de la chambre et température) a également été étudiée.Pour aller plus loin, le MPL in-situ, basé sur la technique de photoluminescence modulée, est conçu pour étudier quantitativement les propriétés des matériaux semi-conducteurs. Cet outil de caractérisation utilise un laser à modulation d'intensité pour exciter l'échantillon, afin de pouvoir mesurer la durée de vie des porteurs minoritaires. Après la conceptualisation et la fabrication d'un nouveau système d'acquisition optique, l'étalonnage du système et l'optimisation des paramètres MPL ont été réalisés. En outre, une méthode de caractérisation a également été développée, de sorte que le MPL in situ est capable de mesurer la durée de vie des porteurs minoritaires à une densité de porteurs minoritaires souhaité (par exemple, 10^15 cm^-3 pour une cellule solaire à une jonction non concentrée). Après de nombreux travaux, l'outil est maintenant fonctionnel et a été utilisé pour mesurer la durée de vie des porteurs minoritaires de silicium cristallin pendant le dépôt de la couche de passivation a-Si:H, le traitement thermique et le dépôt de nitrure de silicium (a-SiNx:H). Les résultats expérimentaux montrent que la température à laquelle les processus ont été conduits joue un rôle majeur dans l'activation et la modification des propriétés de passivation de surface fournies par Al2O3.Enfin, alors que la tendance à la cellule solaire tandem augmente rapidement, un autre outil de caractérisation in-situ, appelé PLt in-situ (photoluminescence in-situ pour cellule solaire tandem), a été développé. Cet outil de caractérisation résulte d'une combinaison de technique de steady-state photoluminescence et de photoluminescence modulée. Il a été conçu pour étudier en temps réel les propriétés des deux sous-cellules, indépendamment et simultanément. Le PLt in-situ peut être un outil de caractérisation potentiel pour la recherche sur les cellules solaires tandem à haute efficacitéDuring the last few decades, the conversion efficiency of photovoltaic solar cell has been significantly improved, almost reaching the Shockley-Queisser theoretical limit. At this point, a profound understanding of material properties and its evolution during the solar cell fabrication processes become increasingly crucial to further improve the cell conversion efficiency. For this reason, my doctoral studies have been focused on the development of in-situ characterization tools, which allows the studies of material properties in real time during the processes. The tools were developed based on photoluminescence techniques, in which the sample (semiconductor materials) is optically excited and simultaneously emits photons with energy approximately equal to the band gap of materials. In this thesis, three in-situ characterization tools will be presented.In-situ SSPL, based on steady-state photoluminescence technique, is developed to study the properties of semiconductor materials during the processes by directly measuring the steady-state PL intensity. After the upgrade of optical acquisition system, the tool has been used extensively to study the evolution of surface properties of crystalline silicon wafer, passivated by aluminum oxide (Al2O3) grown by atomic layer deposition (ALD) and hydrogenated amorphous silicon (a-Si:H) grown by plasma-enhanced chemical vapor deposition (PECVD), under Ar/H2 plasma exposure at different conditions. From these experiments, the behavioral differences between Al2O3-passivated sample and a-Si:H-passivated sample was observed and discussed. In addition, thanks to the plasma exposure experiment through a magnesium fluoride optical window (MgF2), the root cause of plasma-induced degradation of surface passivation was pin-pointed. Last but not least, the relationship between the dynamic of plasma-induced degradation and the plasma parameters (e.g. applied RF power, chamber pressure, and temperature) was also studied.To go one step further, in-situ MPL, based on modulated photoluminescence technique, is built to quantitatively study the properties of semiconductor materials. This characterization tool employs an intensity-modulated laser to excite the sample, so the minority carrier lifetime can be measured. After the conceptualization and fabrication of a new optical acquisition system, the system calibration and the optimization of MPL parameters were conducted. Furthermore, a characterization method was also developed, so the in-situ MPL is able to measure the minority carrier lifetime at a defined minority carrier density (e.g. 1015 cm-3 for non-concentrated single junction solar cell). After a lot of work, the tool is now fully functional and has been used to measure the minority carrier lifetime of crystalline silicon wafer during the de position of a-Si:H passivation layer, the thermal treatment, and the deposition of hydrogenated amorphous silicon nitride (a-SiNx:H) anti-reflection coating. The experimental results show that the temperature at which the processes were conducted plays a major role in activation and modification of surface passivation properties provided by Al2O3.Finally, as the tendency toward tandem solar cell has been continuously growing, another in-situ characterization tool, known as in-situ PLt (in-situ photoluminescence for tandem solar cell), was built. This characterization tool results from a combination of steady-state photoluminescence and modulated photoluminescence technique and was designed to study in real time the properties of both sub-cells independently and simultaneously. The in-situ PLt can be a potential characterization tool for the research toward high efficiency tandem solar cell
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De, Vecchi Sylvain. „Développement de cellules photovoltaïques à hétérojonction de silicium et contacts interdigités en face arrière“. Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0050/document.
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Cette thèse est axée sur la fabrication et l’optimisation d’une nouvelle structure permettant théoriquement d’améliorer les performances des cellules à base de silicium cristallin. Cette nouvelle architecture de cellule utilise la technologie des hétérojonctions de silicium a-Si:H/ c-Si (Si-HJ) appliquée sur des structures à contacts interdigités en face arrière (IBC). Le potentiel de rendement des cellules IBC Si-HJ est supérieur à 25%, mais leur fabrication nécessite une localisation des couches de a-Si:H de dopage différent et de leurs métallisations. L’intégration de ces étapes dans un procédé simplifié utilisant des techniques industrielles (PECVD, pulvérisation, sérigraphie et laser) a été étudiée. De plus, une structure obtenue sans séparation entre le BSF et l’émetteur est présentée, permettant de réduire le nombre d’étapes de fabrication. Les avantages ainsi que les limites liés à cette architecture simplifiée ont été illustrés du point de vue expérimental et par simulation. Dans le cadre de ces travaux, le rendement maximum atteint sur les dispositifs IBC Si-HJ simplifiés de 25cm² est de 19% (substrats de type n), ce qui constitue le 3e meilleur résultat au niveau mondial. Les performances des cellules restent encore limitées par l’absorption des couches de a-Si:H utilisées pour la passivation de la face avant, et par la conductivité des couches dopées en face arrière. De nombreuses pistes d’amélioration sont explorées dans cette étude. Un procédé de métallisation innovant a également été élaboré pour le passage sur des substrats de grande taille (150cm²). Il permet de limiter les pertes résistives tout en offrant de la flexibilité au niveau de la géométrie des contacts. La mise en module de cellules ayant ce design de métallisation a ensuite été étudiée, et un module de 4 cellules IBC Si-HJ a pu être fabriquéThis thesis studies the fabrication and the optimization of a new structure to enhance the efficiency of crystalline silicon based solar cells. This new cell design uses a-Si:H/c-Si heterojunction (Si-HJ) technology applied on interdigitated back contact structures (IBC). With IBC Si-HJ solar cells, the efficiency potential is theoretically higher than 25%. Their fabrication requires to pattern doped a-Si:H and the associated metallization on the same side. The implementation of those process steps has been carefully studied. All processes used in this study are potentially industrial (PECVD, sputtering, screen-printing, and laser) and the obtained structure without buffer layer between the BSF and the emitter allows to reduce fabrication steps. Issues linked to this design have been investigated. Within the frame of this work, the maximum efficiency reached on reduced size devices (25cm²) with n-type substrate and is 19% which is the 3rd best result worldwide. The cell performances are still limited by the absorption of front surface passivating layer (a-Si:H) and by the low doped layer conductivity. Several optimization ways are explored in this study. An innovative metallization process is then elaborated to allow large area solar cell fabrication while limiting resistive losses and offering more flexibility on metallized pattern. The interconnection and the encapsulation of cells with this metallization design have been illustrated and a module with 4 cells has been fabricated
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Lundin, Johan. „EROI of crystalline silicon photovoltaics : Variations under different assumptions regarding manufacturing energy inputs and energy output“. Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-199639.
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Installed photovoltaic nameplate power have been growing rapidly around the worldin the last few years. But how much energy is returned to society (i.e. net energy) by this technology, and which factors contribute the most to the amount of energy returned? The objective of this thesis was to examine the importance of certain inputs and outputs along the solar panel production chain and their effect on the energy return on (energy) investment (EROI) for crystalline wafer-based photovoltaics. A process-chain model was built using publicly available life-cycle inventory (LCI) datasets. This model has been kept simple in order to ensure transparency. Univariate sensitivity analysis for processes and multivariate case studies was then applied to the model. The results show that photovoltaic EROI values are very sensitive to assumptions regarding location and efficiency. The ability of solar panels to deliver net energy in northern regions of the earth is questionable. Solar cell wafer thickness have a large impact on EROI, with thinner wafers requiring less silicon material. Finding an alternative route for production of solar-grade silicon is also found to be of great importance, as is introduction of kerf loss recycling. Equal system sizes have been found to yield an primary EROI between approximately 5.5-19 depending on location and assumptions. This indicates that a generalized absolute EROI for photovoltaics may be of little use for decision-makers. Using the net energy cliff concept in relation to primary EROI found in this thesis shows that primary EROI rarely decreases to less than the threshold of 8:1 in univariate cases. Crystalline photovoltaics under similar system boundaries as those in the thesis model does not necessarily constrain economic growth on an energetic basis.
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Yandt, Mark. „Characterization Techniques and Optimization Principles for Multi-Junction Solar Cells and Maximum Long Term Performance of CPV Systems“. Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35870.
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Two related bodies of work are presented, both of which aim to further the rapid development of next generation concentrating photovoltaic systems using high efficiency multi junction solar cells. They are complementary since the characterization of commercial devices and the systematic application of design principles for future designs must progress in parallel in order to accelerate iterative improvements.
First addressed, is the field characterization of state of the art concentrating photovoltaic systems. Performance modeling and root cause analysis of deviations from the modeling results are critical for bringing reliable high value products to the market. Two complementary tools are presented that facilitate acceleration of the development cycle. The “Dynamic real-time I V Curve Measurement System…” provides a live picture of the current-voltage characteristics of a CPV module. This provides the user with an intuitive understanding of how module performance responds under perturbation. The “Shutter technique for noninvasive individual cell characterization in sealed concentrating photovoltaic modules,” allows the user to probe individual cell characteristics within a sealed module. This facilitates non-invasive characterization of modules that are in situ. Together, these tools were used to diagnose the wide spread failure of epoxy connections between the carrier and the emitter of bypass diodes installed in sealed commercial modules.
Next, the optimization principals that are used to choose energy yield maximizing bandgap combinations for multi-junction solar cells are investigated. It is well understood that, due to differences in the solar resource in different geographical locations, this is fundamentally a local optimization problem. However, until now, a robust methodology for determining the influences of geography and atmospheric content on the ideal design point has not been developed. This analysis is presented and the influence of changing environment on the representative spectra that are used to optimize bandgap combinations is demonstrated. Calculations are confirmed with ground measurements in Ottawa, Canada and the global trends are refined for this particular location. Further, as cell designers begin to take advantage of more flexible manufacturing processes, it is critical to know if and how optimization criteria must change for solar cells with more junctions. This analysis is expanded to account for the differences between cells with up to 8 subcell bandgaps.
A number of software tools were also developed for the Sunlab during this work. A multi-junction solar cell model calibration tool was developed to determine the parameters that describe each subcell. The tool fits a two diode model to temperature dependent measurements of each subcell and provides the fitting parameters so that the performance of multi-junction solar cells composed of those subcells can be modeled for real world conditions before they are put on-sun. A multi-junction bandgap optimization tool was developed to more quickly and robustly determine the ideal bandgap combinations for a set of input spectra. The optimization process outputs the current results during iteration so that they may be visualized. Finally, software tools that compute annual energy yield for input multi-junction cell parameters were developed. Both a brute force tool that computes energy harvested at each time step, and an accelerated tool that first bins time steps into discrete bins were developed. These tools will continue to be used by members of the Sunlab.
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Hub, Michal. „Návrh fotovoltaické elektrárny s bateriovým úložištěm pro rodinný dům“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442441.
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This diploma thesis deals with the design of a photovoltaic power plant with a battery storage for a family house. In the theoretical part at first the principle of photovoltaic cells is analysed together with the various types used in this branch. Furthermore, the thesis deals with the description of photovoltaic systems and its individual parts consisting of inverters and accumulators. This thesis analyses the object for the installation of a photovoltaic power plant, including legislative and subsidy conditions. In the final part, itself system is analysed with a price proposal.
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Andersson, August. „Electrical performance study of organic photovoltaics for indoor applications : with potential in Internet of Things devices“. Thesis, Karlstads universitet, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-78104.
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The evolution of the internet of things (IoT) opens the market opportunity for organic photovoltaic cells, especially for indoor applications where the lifetime of the organic cells is longer than outdoor. For example, IoT requires off-grid energy sources for many devices with low power consumption. In this work, new materials were tested as candidate components in the active layer of printed organic photovoltaics by fabrication of devices. The initial electrical performance of these devices and their stability over time were investigated by measurements of the current-voltage characteristics. Three selected active layers were further investigated with atomic force microscopy (AFM) measurements. The current-voltage measurements showed that the addition of a solvent additive to the active layer ink affects the initial electrical performance as well as the stability of the devices. The AFM measurements showed that the surface topography of the active layer was affected by the sort of solvent additive that was used. Three new electron acceptor material and two solvent additives showed promising electrical performance and stability.
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Gonzalez, Maria. „Electronic Defects of III-V Compound Semiconductor Materials Grown on Metamorphic SiGe Substrates for Photovoltaic Applications“. The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250703650.
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Vauche, Laura. „Process development and scale-up for low-cost high-efficiency kesterite thin film photovoltaics“. Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4355/document.
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Dans un contexte général d’augmentation de la demande énergétique et de préoccupation croissante face au réchauffement climatique et à la limitation des ressources naturelles, l’utilisation d’énergie solaire devrait augmenter. L’avenir des différentes technologies photovoltaïques dépend évidemment de leur rendement de conversion photovoltaïque et de leur coût mais aussi de la disponibilité des ressources. Les couches minces de kesterite, Cu2ZnSnS4 (CZTS), Cu2ZnSnSe4 (CZTSe) ou Cu2ZnSn(S,Se)4 (CZTSSe), composées d’éléments abondants dans la croûte terrestre se positionnent en candidat prometteur pour la conversion d’énergie solaire à grande échelle.Dans cette thèse, l’électro-dépôt, un procédé compatible avec des exigences industrielles de production, est utilisé pour déposer un précurseur de cuivre, étain et zinc sur des substrats de 15 × 15 cm2, de composition et épaissseur contrôlables. Ce précurseur est ensuite converti en semiconducteur par traitement thermique en présence de soufre ou de sélénium. Les couches ainsi formées de Cu-Zn-Sn-S ou Cu-Zn-Sn-Se, doivent être uniformes et présenter les propriétés appropriées (phases, composition, morphologie) pour la fabrication de cellules solaires à haut rendement. Le procédé de fabrication de la cellule solaire complète, notamment les étapes qui interviennent dans la formation de la jonction p-n (décapage chimique et dépôt de couche tampon) est également optimisé pour maximiser les rendements. A l’issue de ces optimisations, un rendement de 9.1% est obtenu pour une cellule solaire CZTSe, un nouveau record pour les cellules solaires à base de kesterite fabriquées par électro-dépôtFacing growing energy demand and increasing concerns about climate change and finite energy sources, solar energy use should increase. The future of the different photovoltaic technologies obviously depends on their power conversion efficiency and cost (summarized by the ratio cost per watt), but also on the elements availability. Thin films of earth-abundant kesterite, Cu2ZnSnS4 (CZTS), Cu2ZnSnSe4 (CZTSe) or Cu2ZnSn(S,Se)4 (CZTSSe), which can be manufactured with low-cost processes, are promising candidates for solar energy conversion at large scale.In this thesis, a copper tin and zinc precursor of controllable composition and thickness is electrodeposited on 15 × 15 cm2 substrates. Electrodeposition is a process compatible with high throughput low-cost and safety industry requirements. The precursor is converted into a semiconductor by thermal treatments in presence of sulfur or selenium. The resulting Cu-Zn-Sn-S or Cu-Zn-Sn-Se layers should be uniform and have adequate properties (phases, composition and morphology) to produce high efficient solar cells. Full device processing, including the pn junction formation steps (wet chemical etching and buffer layer deposition) is also investigated in order to maximize device efficiency. The best CZTSe solar cell exhibits a 9.1% powerconversion efficiency, setting a new record for kesterite solar cells produced by electrodeposition
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Lepík, Pavel. „Inovace systému pro detekci defektů solárních článků pomocí elektroluminiscence“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-318492.
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This master thesis analyses the existing methods both practically and theoretically used to detect defected surface area in solar cells. Various methods were used but by using an upgraded CMOS camera without IR filter to implement the electroluminescence method, this has proven to have a very crucial impact on the results. Given the overall results and the acquired information, a procedure with a simple parameter can be setup to carry out the measurements. In addition to this a catalog was formed showing the defects occurring in mono and polycrystalline solar cells.
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Stranks, Samuel David. „Investigating carbon nanotube - polymer blends for organic solar cell applications“. Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:3a65d509-1610-4517-b10d-c90d832134c3.
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This thesis describes studies on nanohybrid systems consisting of single-walled carbon nanotubes (SWNTs) with monolayer coatings of semiconducting polymers. Steady-state and time-resolved optical and high-resolution microscopy experiments were used to investigate the blends. These materials show promise for use in organic photovoltaics (OPVs) owing to the high carrier mobilities and large aspect ratios of SWNTs, the controllable solubilisation of tubes with various polymers and the broad light-harvesting abilities of organic polymers. Chapters 1 and 2 introduce the theory and background behind the work and present a literature review of previous work utilising carbon nanotubes in OPV devices, revealing poor performances to date. The experimental methods used during the thesis are detailed in Chapter 3 and the solution processing techniques used to prepare the polymer–nanotube blend samples are described in Chapter 4. Chapter 5 describes a study on a nanotube blend with a thiophene polymer, a system previously unsuccessfully implemented into OPV devices. Ultrafast spectroscopic measurements showed that electrons can transfer on a 400 fs time scale from the polymer to nanotubes and the conditions to allow long-lived free charges to be produced were found. The study is extended in Chapter 6 to show that nanostructures consisting of a nanotube coated in one polymer can then be coated by a second polymer and that these nano-engineered structures could be implemented into OPV devices. The use of a competition binding process to isolate purely semiconducting nanotubes dispersed with any desired polymer is then described in Chapter 7. Finally, Chapter 8 introduces systems consisting of chains of porphyrin units, nature’s light-harvesting systems, bound to nanotubes and the blends were found to exhibit the required electronic alignment for use in OPVs. The work described in this thesis provides an explanation for the poor device behaviour of nanotube–polymer blends to date and, in particular, demonstrates several nanohybrid systems that show particular promise for improved OPV applications.
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Gabr, Ahmed. „Modelling and Characterization of Down-Conversion and Down-Shifting Processes for Photovoltaic Applications“. Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35048.
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Down-conversion (DC) and down-shifting (DS) layers are optical layers mounted on the top surface of a solar cell that can potentially increase the solar cell efficiency. The effect of DC and DS layers to enhance the performance of single-junction solar cells has been studied by means of simulation and experimental work. In this thesis a model is developed to study the effects of DC and DS layers by modifying the incident spectrum. The effect of the layers on ideal cells as well as commercial grade silicon and CIGS solar cells that are modeled in a device simulator is examined.
Silicon nanocrystals (Si-nC) embedded in a silicon dioxide matrix to act as a DS layer were fabricated and characterized at McMaster University as part of this project. The measured optical properties as well as the photoluminescence measurements are used as input parameters to the optical model. The enhancement due to the Si-nC when coupled to silicon and CIGS solar cells is explored. Beside the DC and DS effects, there is also disturbance to the surface reflections due to the addition of a new layer to the top surface and is referred to as antireflection coating (ARC) effect. For the simulated silicon solar cell under the standard AM1.5G spectrum (1000W/m2), a maximum increase in Jsc of 8.4% is achieved for a perfect DS layer as compared to a reference cell, where 7.2% is due to ARC effect and only 1.2% is due to DS effect. On the other hand, there is an increase in Jsc of 19.5% for the CIGS solar cell when coupled to a perfect DS layer. The DS effect is dominant with 18%, while the ARC effect contributes only 1.5% to the total Jsc enhancement.
Accurately characterizing DS layers coupled to solar cell requires knowledge of optical properties of the complete structure. Internal quantum efficiency is an important tool for characterizing DS systems, nevertheless, it is rarely reported. In addition, the ARC effect is not experimentally decoupled from the DS effect. In this work, a straightforward method for calculating the active layer contribution that minimizes error by subtracting optically-modeled electrode absorption from experimentally measured total absorption.
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Ro, Kyoungsoo. „Two-Loop Controller for Maximizing Performance of a Grid-Connected Photovoltaic-Fuel Cell Hybrid Power Plant“. Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30378.
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The study started with the requirement that a photovoltaic (PV) power source should be integrated with other supplementary power sources whether it operates in a stand-alone or grid-connected mode. First, fuel cells for a backup of varying PV power were compared in detail with batteries and were found to have more operational benefits. Next, maximizing performance of a grid-connected PV-fuel cell hybrid system by use of a two-loop controller was discussed. One loop is a neural network controller for maximum power point tracking, which extracts maximum available solar power from PV arrays under varying conditions of insolation, temperature, and system load. A real/reactive power controller (RRPC) is the other loop.
The RRPC meets the system's requirement for real and reactive powers by controlling incoming fuel to fuel cell stacks as well as switching control signals to a power conditioning subsystem. The RRPC is able to achieve more versatile control of real/reactive powers than the conventional power sources since the hybrid power plant does not contain any rotating mass. Results of time-domain simulations prove not only effectiveness of the proposed computer models of the two-loop controller, but also their applicability for use in transient stability analysis of the hybrid power plant. Finally, environmental evaluation of the proposed hybrid plant was made in terms of plant's land requirement and lifetime CO2 emissions, and then compared with that of the conventional fossil-fuel power generating forms.Ph. D.
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Carlin, Andrew Michael. „Materials Integration and Metamorphic Substrate Engineering from Si to GaAs to InP for Advanced III-V/Si Photovoltaics“. The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354648645.
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Ranjan, Vikash. „Enhancement of the Deposition Processes of Cu(In,Ga)Se2 and CdS Thin Films via In-situ and Ex-situ Measurements for Solar Cell Application“. University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1300213130.
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Kaderka, Tomasz. „Automatické měřicí pracoviště U-I charakteristik solárních článků“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219206.
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The theoretical part is to outline the possibilities of solar energy conversion, learn about the issues solar cells and describe the history of photovoltaics and photovoltaic energy conversion. Then describe principle of the measurement VA characteristics of photovoltaic cells. This issue is not as easy as it seems at first sight, because the solar cell isn’t a linear component, which is very easy to measure. Analysis of VA characteristic of photovoltaic cells affects parameters such as: light intensity, temperature, serial and parallel resistance, the slope of the light source, and more. The practical part deals with creating a workplace for automatic measurement of VA characteristics of photovoltaic cells in the LabVIEW. Challenge is to create a functional program, which automatically measures the VA characteristics not only in the lighted cells, but also in the shaded cell (diode mode). The program calculates the power and important parameters, such as short-circuit current, open circuit voltage, maximum power, current and voltage at maximum power article. The program allows you to export the measured values to a text file. In the last chapter of this work is made control measurements of three samples of monocrystal photovoltaic cell by the measuring workplace. The measurement is compared with the reference device Solar Cell Tester.
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Horváth, Radovan. „Návrh skladby zdrojů pro síťovou nezávislost“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-254307.
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The aim of this diploma thesis is the development of research on the topic of the draft mix for network independence. Next is the outline the various design solutions of the battery systems for accumulation electric energy and balance model energy supply system for the selected object. The practical part of diploma thesis deals with necessary resources and the size of batteries for autonomous operation during the summer months and also implements technical and economic studies aimed at finding cost-effective solutions. The work is divided into 6 chapters that contain 16 tables and 18 figures. Diploma thesis brings an option to configure a photovoltaic system and also describes the features, functions and the choice between the most used technologies. Evaluation of results of theoretical methods are described in the final part.
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Osorio, Ruy Sebastian Bonilla. „Surface passivation for silicon solar cells“. Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:46ebd390-8c47-4e4b-8c26-e843e8c12cc4.
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Passivation of silicon surfaces remains a critical factor in achieving high conversion efficiency in solar cells, particularly in future generations of rear contact cells -the best performing cell geometry to date. In this thesis, passivation is characterised as either intrinsic or extrinsic, depending on the origin of the chemical and field effect passivation components in dielectric layers. Extrinsic passivation, obtained after film deposition or growth, has been shown to improve significantly the passivation quality of dielectric films. Record passivation has been achieved leading to surface recombination velocities below 1.5 cm/s for 1 Ωcm n-type silicon covered with thermal oxide, and 0.15 cm/s in the same material covered with a thermal SiO2/PECVD SiNx double layer. Extrinsic field effect passivation, achieved by means of corona charge and/or ionic species, has been shown to decrease by 3 to 10 times the amount of carrier recombination at a silicon surface. A new parametrisation of interface charge, and electron and hole recombination velocities in a Shockley-Read-Hall extended formalism has been used to model accurately silicon surface recombination without the need to incorporate a term relating to space-charge or surface damage recombination. Such a term is unrealistic in the case of an oxide/silicon interface. A new method to produce extrinsic field effect passivation has been developed in which charge is introduced into dielectric films at high temperature and then permanently quenched in place by cooling to room temperature. This approach was investigated using charge due to one or more of the following species: ions produced by corona discharge, Na+, K+, Cs+, Mg2+ and Ca2+. It was implemented on both single SiO2 and double SiO2/SiNx dielectric layers which were then measured for periods of up to two years. The decay of the passivation was very slow and time constants of the order of 10,000 days were inferred for two systems: 1) corona-charge-embedded into oxide grown on textured FZ-Si, and 2) potassium ions driven into an oxide on planar FZ-Si. The extrinsic field effect passivation methods developed in this work allow more flexibility in the combined optimisation of the optical properties and the chemical passivation properties of dielectric films on semiconductors. Increases in cell Voc, Jsc and η parameters have been observed in simulations and obtained experimentally when extrinsic field effect passivation is applied to the front surface of silicon solar cells. The extrinsic passivation reported here thus represents a major advancement in controlled and stable passivation of silicon surfaces, and shows great potential as a scalable and cost effective passivation technology for solar cells.
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Leal, Ronan. „Epitaxial growth of silicon by PECVD from SiF4/H2/Ar gas mixtures for photovoltaics“. Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX038.
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Cette thèse de doctorat évalue le potentiel de la croissance épitaxiale à basse température (200-300°C) par dépôt chimique en phase vapeur assisté par plasma à partir de SiF4/H2/Ar pour la formation de l’émetteur dans des cellules solaires de type nPERT. La première partie concerne l’identification et l’optimisation des conditions de dépôt pour réaliser des couches épitaxiées faiblement contraintes avec une interface epi/wafer de bonne qualité. La perte d’épitaxie a également été étudiée et nous avons mis en évidence que la formation de macles au cours de la croissance était responsable de la dégradation de la cristallinité. Ensuite, l’étude des mécanismes de croissance a été menée et l’analyse des phases initiales de croissance a permis d’identifier un mode de croissance de type Volmer-Weber.Les conditions de dépôt ont ensuite été transférées à un réacteur PECVD semi-industriel de 6 pouces. Les problèmes d’homogénéité et de vitesse de croissance ont été abordés par le design d’une nouvelle « shower head » grâce aux simulations d’écoulement du gaz. Des couches épitaxiées dopées bore avec un dopage de type p de 4.1019 cm-3 et une efficacité de dopage jusqu’à 70% ont ainsi été fabriquées à seulement 300°C. La vitesse de croissance dans ces conditions atteint 1.1 Å/s, i.e. 15 fois plus rapide que les premiers résultats obtenus. Enfin, la passivation des couches épitaxiées a été étudiée et un temps de vie de 160 μs a été obtenu sur des couches intrinsèques de 200 nm d’épaisseur passivées avec 10 nm d’oxyde d’aluminiumThis doctoral work aimed to assess the potential of low-temperature (200-300°C) epitaxy by plasma-enhanced chemical vapor deposition (PECVD) using SiF4/H2/Ar gas mixtures for the emitter formation in nPERT solar cells. The first part of this PhD thesis concerned the identification and the optimization of the process conditions to perform lowly strained intrinsic epi-layers with a smooth epi/wafer interface. We also investigated the causes of epitaxy breakdown and found out that a twinning-induced mechanism was responsible. Subsequently we focused on the growth mechanisms by studying the initial stages of growth and a Volmer-Weber growth mode has been highlighted. Finally, the process conditions for intrinsic epitaxy were transferred from a researchPECVD reactor to a 6 inch semi-industrial one. Inhomogeneity and growth rate issues have been tackled by fluid dynamics simulations resulting in the design of a new shower head. Boron-doped epi-layers grown at 300°C with an as-deposited hole concentration of 4.1019 cm-3 and a doping efficiency up to 70 % have been achieved keeping a low mosaicity and a low variation of the lattice parameter. The growth rate in these conditions reached 1.1 Å/s, i.e 15 times higher than what obtained at the beginning of this PhD for boron-doped epi-layers. Finally, the passivation of epitaxial layers has been investigated and lifetimes up to 160 μs for a 200 nm thick intrinsic layer passivated with
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Nylund, Sophie, und Zahra Barbari. „Study of defects in PV modules : UV fluorescence and Thermographic photography for Photovoltaics (PV) Field Application“. Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-44120.
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For a PV plant it is of fundamental importance that the operation of the PV modules is free from faults or at least that the faults can be detected early, to ensure efficient electricity production. Some defects such as cracks can be seen in visible light while microcracks and damage to the silicon material can only be seen through special lighting. This study focuses on the most common defects in photovoltaic (PV) systems. Compare the infrared (IR) technology with the new ultraviolet (UV) fluorescence image technique for PV characterization, based on their accuracy and uncertainty factors under an experimental field investigation. In this study, first a literature study was conducted to the most common defects in PV system and their impact on electricity generation. Then a simulation model of a PV system was created in PVsyst and exported to Microsoft Excel which was used to evaluate how different defects at different stages of the PV cell's life cycle impact electricity generation, performance parameters and economic exchange. Furthermore, experiments with UV and IR was implemented at a PV system located in Dalarna and some PV modules at MDH. It was conducted that occurrence of snail tracks, delamination and hot spots in combination with bypass failures and non-functioning cell will affect the economic profitability in the long run and the payback time will increase since their impacts on electricity generation and performance parameters are huge. The worst case is when PV modules are affected by the fault in bypass diode and non-functioning cell which result to a payback time longer than the module's lifetime and huge amount electricity losses in different bypass diodes configurations. Since UV and IR are two different methods that are performed in two different ways, different errors occurred during the measurements. The biggest external factor was the weather that determined if the experiment could be implemented. The IR method gave decent results and was quicker to use, but the UV method highlighted some defect which could not be seen with the IR technology.
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Sun, Leizhi. „Improved Thin Film Solar Cells Made by Vapor Deposition of Earth-Abundant Tin(II) Sulfide“. Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11539.
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Tin(II) sulfide (SnS) is an earth-abundant, inexpensive, and non-toxic absorber material for thin film solar cells. SnS films are deposited by atomic layer deposition (ALD) through the reaction of a tin precursor, bis(N,N'-diisopropylacetamidinato)tin(II), and hydrogen sulfide. The SnS films demonstrate excellent surface morphology, crystal structure, phase purity, stoichiometry, elemental purity, and optical and electrical properties.Engineering and Applied Sciences
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Mohammadi, Farid. „A Meta-Analysis on Solar Cell Technologies“. Thesis, Mittuniversitetet, Avdelningen för elektronikkonstruktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-32584.
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The objective of this study is analysing the characteristics of five different solar cell technologies regarding their efficiency, fill factor, cost and environmental impacts and comparing their improvement records over years considering their efficiency. The five solar cell technologies of interest are amorphous silicon, monocrystalline silicon, polycrystalline silicon, cupper indium gallium selenide thin film and cadmium telluride thin film. The structure and manufacturing process of each of cell technologies were discussed. The study was conducted by the aid of available scientific reports regarding the electrical characteristics of different solar cell technologies. The extracted information regarding efficiency rate and fill factor was analysed using graphs and significant findings are discussed. The five technologies are also compared regarding their cost and ease of fabrication and their impacts on environment and recycling challenges. The result of this study is suggesting the most promising technology that may be the optimal option for further investment and research.
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Al, Kadi Jazairli Mohamad. „Growth of Zinc Oxide Nanoparticles on Top of Polymers and Organic Small Molecules as a Transparent Cathode in Tandem Photovoltaic Device“. Thesis, Linköping University, Department of Science and Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11391.
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Organic solar cells have caught considerable attention in the past few years due to their potential for providing environmentally safe, flexible, lightweight, inexpensive, and roll-to-roll feasible production solar cells. However, the efficiency achieved in current organic solar cells is quite low, yet quick and successive improvements render it as a promising alternative. A hopeful approach to improve the efficiency is by exploiting the tandem concept which consists of stacking two or more organic solar cells in series.
One important constituent in tandem solar cells is the middle electrode layer which is transparent and functions as a cathode for the first cell and an anode for the second cell. Most studies done so far have employed noble metals such as gold or silver as the middle electrode layer; however, they suffered from several shortcomings especially with respect to reproducibility.
This thesis focuses on studying a new trend which employs an oxide material based on nano-particles as a transparent cathode (such as Zinc-oxide-nano-particles) along with a transparent anode so as to replace the middle electrode.
Thus, this work presents a study on solution processable zinc oxide (ZnO) nanostructures, their proper handling techniques, and their potential as a middle electrode material in Tandem solar cells in many different configurations involving both polymer and small molecule materials. Moreover, the ZnO-np potential as a candidate for acceptor material is also investigated.
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Kirsanova, Maria. „Engineering of Semiconductor Nanocomposites for Harvesting and Routing of Optical Energy“. Bowling Green State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1308104239.
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Saliba, Michael. „Plasmonic nanostructures and film crystallization in perovskite solar cells“. Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:fdb36a9e-ddf5-4d27-a8dc-23fffe32a2c5.
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The aim of this thesis is to develop a deeper understanding and the technology in the nascent field of solid-state organic-inorganic perovskite solar cells. In recent years, perovskite materials have emerged as a low-cost, thin-film technology with efficiencies exceeding 16% challenging the quasi-paradigm that high efficiency photovoltaics must come at high costs. This thesis investigates perovskite solar cells in more detail with a focus on incorporating plasmonic nanostructures and perovskite film formation. Chapter 1 motivates the present work further followed by Chapter 2 which offers a brief background for solar cell fabrication and characterisation, perovskites in general, perovskite solar cells in specific, and plasmonics. Chapter 3 presents the field of plasmonics including simulation methods for various core-shell nanostructures such as gold-silica and silver-titania nanoparticles. The following Chapters 4 and 5 analyze plasmonic core-shell metal-dielectric nanoparticles embedded in perovskite solar cells. It is shown that using gold@silica or silver@titania NPs results in enhanced photocurrent and thus increased efficiency. After photoluminescence studies, this effect was attributed to an unexpected phenomenon in solar cells in which a lowered exciton binding energy generates a higher fraction of free charge. Embedding thermally unstable silver NPs required a low-temperature fabrication method which would not melt the Ag NPs. This work offers a new general direction for temperature sensitive elements. In Chapters 6 and 7, perovskite film formation is studied. Chapter 6 shows the existence of a previously unknown crystalline precursor state and an improved surface coverage by introducing a ramped annealing procedure. Based on this, Chapter 7 investigates different perovskite annealing protocols. The main finding was that an additional 130°C flash annealing step changed the film crystallinity dramatically and yielded a higher orientation of the perovskite crystals. The according solar cells showed an increased photocurrent attributed to a decrease in charge carrier recombination at the grain boundaries. Chapter 8 presents on-going work showing noteworthy first results for silica scaffolds, and layered, 2D perovskite structures for application in solar cells.
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Hansson, Rickard. „Morphology and material stability in polymer solar cells“. Licentiate thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-37843.
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Polymer solar cells are promising in that they are inexpensive to produce, and due to their mechanical flexibility have the potential for use in applications not possible for more traditional types of solar cells. The performance of polymer solar cells depends strongly on the distribution of electron donor and acceptor material in the active layer. Understanding the connection between morphology and performance as well as how to control the morphology, is therefore of great importance. Furthermore, improving the lifetime of polymer solar cells has become at least as important as improving the efficiency. In this thesis, the relation between morphology and solar cell performance is studied, and the material stability for blend films of the thiophene-quinoxaline copolymer TQ1 and the fullerene derivatives PCBM and PC70BM. Atomic force microscopy (AFM) and scanning transmission X-ray microscopy (STXM) are used to investigate the lateral morphology, secondary ion mass spectrometry (SIMS) to measure the vertical morphology and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to determine the surface composition. Lateral phase-separated domains are observed whose size is correlated to the solar cell performance, while the observed TQ1 surface enrichment does not affect the performance. Changes to the unoccupied molecular orbitals as a result of illumination in ambient air are observed by NEXAFS spectroscopy for PCBM, but not for TQ1. The NEXAFS spectrum of PCBM in a blend with TQ1 changes more than that of pristine PCBM. Solar cells in which the active layer has been illuminated in air prior to the deposition of the top electrode exhibit greatly reduced electrical performance. The valence band and absorption spectrum of TQ1 is affected by illumination in air, but the effects are not large enough to account for losses in solar cell performance, which are mainly attributed to PCBM degradation at the active layer surface.The performance of polymer solar cells depends strongly on the distribution of electron donor and acceptor material in the active layer. Understanding the connection between morphology and performance as well as how to control the morphology, is therefore of great importance. Furthermore, improving the lifetime has become at least as important as improving the efficiency for polymer solar cells to become a viable technology. In this work, the relation between morphology and solar cell performance is studied as well as the material stability for polymer:fullerene blend films. A combination of microscopic and spectroscopic methods is used to investigate the lateral and vertical morphology as well as the surface composition. Lateral phase-separated domains are observed whose size is correlated to the solar cell performance, while the observed surface enrichment of polymer does not affect the performance. Changes to the unoccupied molecular states as a result of illumination in ambient air are observed for the fullerene, but not for the polymer, and fullerenes in a blend change more than pristine fullerenes. Solar cells in which the active layer has been illuminated exhibit greatly reduced electrical performance, mainly attributed to fullerene degradation at the active layer surface.
Paper 2 ingick som manuskript i avhandlingen. Nu publicerad.
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Hřešil, Tomáš. „Analýza chlazení koncentrátorového fotovoltaického článku“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220330.
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This project solves the problem of cooling the photovoltaic cell. Solar cell was modeled according to a real model in SolidWorks, and subsequently created the model was simulated in SolidWorks Flow Simulation and Ansys Fluent. The use of both systems allow a comparison of their possibilities in the field of heat transfer and their suitability for the case. The conclusion summarizes the first results and outline further developments cooling design to optimize the performance of the solar cell.