Dissertations / Theses: 'Silicon solar cells'

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Søiland, Anne Karin. "Silicon for Solar Cells." Doctoral thesis, Norwegian University of Science and Technology, Department of Materials Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-565.

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This thesis work consists of two parts, each with a different motivation. Part II is the main part and was partly conducted in industry, at ScanWafer ASA’s plant no.2 in Glomfjord.The large growth in the Photo Voltaic industry necessitates a dedicated feedstock for this industry, a socalled Solar Grade (SoG) feedstock, since the currently used feedstock rejects from the electronic industry can not cover the demand. Part I of this work was motivated by this urge for a SoG- feedstock. It was a cooperation with the Sintef Materials and Chemistry group, where the aim was to study the kinetics of the removal reactions for dissolved carbon and boron in a silicon melt by oxidative gas treatment. The main focus was on carbon, since boron may be removed by other means. A plasma arc was employed in combination with inductive heating. The project was, however, closed after only two experiments. The main observations from these two experiments were a significant boron removal, and the formation of a silica layer on the melt surface when the oxygen content in the gas was increased from 2 to 4 vol%. This silica layer inhibited further reactions.Multi-crystalline (mc) silicon produced by directional solidification constitutes a large part of the solar cell market today. Other techniques are emerging/developing and to keep its position in the market it is important to stay competitive. Therefore increasing the knowledge on the material produced is necessary. Gaining knowledge also on phenomenas occurring during the crystallisation process can give a better process control.Part II of this work was motivated by the industry reporting high inclusion contents in certain areas of the material. The aim of the work was to increase the knowledge of inclusion formation in this system. The experimental work was divided into three different parts;1) Inclusion study2) Extraction of melt samples during crystallisation, these were to be analysed for carbon- and nitrogen. Giving thus information of the contents in the liquid phase during soldification.3) Fourier Transform Infrared Spectroscopy (FTIR)-measurements of the substitutional carbon contents in wafers taken from similar height positions as the melt samples. Giving thus information of the dissolved carbon content in the solid phase.The inclusion study showed that the large inclusions found in this material are β-SiC and β-Si3N4. They appear in particularly high quantities in the top-cuts. The nitrides grow into larger networks, while the carbide particles tend to grow on the nitrides. The latter seem to act as nucleating centers for carbide precipitation. The main part of inclusions in the topcuts lie in the size range from 100- 1000 µm in diameter when measured by the Coulter laser diffraction method.A method for sampling of the melt during crystallisation under reduced pressure was developed, giving thus the possibility of indicating the bulk concentration in the melt of carbon and nitrogen. The initial carbon concentration was measured to ~30 and 40 ppm mass when recycled material was employed in the charge and ~ 20 ppm mass when no recycled material was added. Since the melt temperature at this initial stage is ~1500 °C these carbon levels are below the solubility limit. The carbon profiles increase with increasing fraction solidified. For two profiles there is a tendency of decreasing contents at high fraction solidified.For nitrogen the initial contents were 10, 12 and 44 ppm mass. The nitrogen contents tend to decrease with increasing fraction solidified. The surface temperature also decreases with increasing fraction solidified. Indicating that the melt is saturated with nitrogen already at the initial stage. The proposed mechanism of formation is by dissolution of coating particles, giving a saturated melt, where β-Si3N4 precipitates when cooling. Supporting this mechanism are the findings of smaller nitride particles at low fraction solidified, that the precipitated phase are β-particles, and the decreasing nitrogen contents with increasing fraction solidified.The carbon profile for the solid phase goes through a maximum value appearing at a fraction solidified from 0.4 to 0.7. The profiles flatten out after the peak and attains a value of ~ 8 ppma. This drop in carbon content is associated with a precipitation of silicon carbide. It is suggested that the precipitation of silicon carbide occurs after a build-up of carbon in the solute boundary layer.FTIR-measurements for substitutional carbon and interstitial oxygen were initiated at the institute as a part of the work. A round robin test was conducted, with the Energy Research Centre of the Netherlands (ECN) and the University of Milano-Bicocci (UniMiB) as the participants. The measurements were controlled against Secondary Ion Mass Spectrometer analyses. For oxygen the results showed a good correspondence between the FTIR-measurements and the SIMS. For carbon the SIMS-measurements were significantly lower than the FTIR-measurements. This is probably due to the low resistivity of the samples (~1 Ω cm), giving free carrier absorption and an overestimation of the carbon content.

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Tarabsheh, Anas al. "Amorphous silicon based solar cells." kostenfrei, 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-29491.

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Al, Tarabsheh Anas. "Amorphous silicon based solar cells." [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-29491.

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Bett, Alexander Jürgen [Verfasser], and Stefan [Akademischer Betreuer] Glunz. "Perovskite silicon tandem solar cells : : two-terminal perovskite silicon tandem solar cells using optimized n-i-p perovskite solar cells." Freiburg : Universität, 2020. http://d-nb.info/1214179703/34.

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Schultz, Oliver. "High-efficiency multicrystalline silicon solar cells." München Verl. Dr. Hut, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=977880567.

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Echeverria, Molina Maria Ines. "Crack Analysis in Silicon Solar Cells." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4311.

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Solar cell business has been very critical and challenging since more efficient and low costs materials are required to decrease the costs and to increase the production yield for the amount of electrical energy converted from the Sun's energy. The silicon-based solar cell has proven to be the most efficient and cost-effective photovoltaic industrial device. However, the production cost of the solar cell increases due to the presence of cracks (internal as well as external) in the silicon wafer. The cracks of the wafer are monitored while fabricating the solar cell but the present monitoring techniques are not sufficient when trying to improve the manufacturing process of the solar cells. Attempts are made to understand the location of the cracks in single crystal and polycrystalline silicon solar cells, and analyze the impact of such cracks in the performance of the cell through Scanning Acoustic Microscopy (SAM) and Photoluminescence (PL) based techniques. The features of the solar cell based on single crystal and polycrystalline silicon through PL and SAM were investigated with focused ion beam (FIB) cross section and scanning electron microscopy (SEM). The results revealed that SAM could be a reliable method for visualization and understanding of cracks in the solar cells. The efficiency of a solar cell was calculated using the current (I) - voltage (V) characteristics before and after cracking of the cell. The efficiency reduction ranging from 3.69% to 14.73% for single crystal, and polycrystalline samples highlighted the importance of the use of crack monitoring techniques as well as imaging techniques. The aims of the research are to improve the manufacturing process of solar cells by locating and understanding the crack in single crystal and polycrystalline silicon based devices.

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Li, Dai-Yin. "Texturization of multicrystalline silicon solar cells." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/64615.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010. Cataloged from PDF version of thesis. Includes bibliographical references (p. 103-111). A significant efficiency gain for crystalline silicon solar cells can be achieved by surface texturization. This research was directed at developing a low-cost, high-throughput and reliable texturing method that can create a honeycomb texture. Two distinct approaches for surface texturization were studied. The first approach was photo-defined etching. For this approach, the research focus was to take advantage of Vall6ra's technique published in 1999, which demonstrated a high-contrast surface texture on p-type silicon created by photo-suppressed etching. Further theoretical consideration, however, led to a conclusion that diffusion of bromine in the electrolyte impacts the resolution achievable with Vallera's technique. Also, diffusion of photocarriers may impose an additional limitation on the resolution. The second approach studied was based on soft lithography. For this approach, a texturization process sequence that created a honeycomb texture with 20 ptm spacing on polished wafers at low cost and high throughput was developed. Novel techniques were incorporated in the process sequence, including surface wettability patterning by microfluidic lithography and selective condensation based on Raoult's law. Microfluidic lithography was used to create a wettability pattern from a 100A oxide layer, and selective condensation based on Raoult's law was used to reliably increase the thickness of the glycerol/water liquid film entrained on hydrophilic oxide islands approximately from 0.2 pm to 2.5 pm . However, there remain several areas that require further development to make the process sequence truly successful, especially when applied to multicrystalline wafers. by Dai-Yin Li. Ph.D.

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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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Zhu, Mingxuan. "Silicon nanowires for hybrid solar cells." Ecole centrale de Marseille, 2013. http://tel.archives-ouvertes.fr/docs/00/94/57/87/PDF/The_manuscript-4.pdf.

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Forster, Maxime. "Compensation engineering for silicon solar cells." Phd thesis, INSA de Lyon, 2012. http://hdl.handle.net/1885/156020.

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This thesis focuses on the effects of dopant compensation on the electrical properties of crystalline silicon relevant to the operation of solar cells. We show that the control of the net dopant density, which is essential to the fabrication of high-efficiency solar cells, is very challenging in ingots crystallized with silicon feedstock containing both boron and phosphorus such as upgraded metallurgical-grade silicon. This is because of the strong segregation of phosphorus which induces large net dopant density variations along directionally solidified silicon crystals. To overcome this issue, we propose to use gallium co-doping during crystallization, and demonstrate its potential to control the net dopant density along p-type and n-type silicon ingots grown with silicon containing boron and phosphorus. The characteristics of the resulting highly-compensated material are identified to be: a strong impact of incomplete ionization of dopants on the majority carrier density, an important reduction of the mobility compared to theoretical models and a recombination lifetime which is determined by the net dopant density and dominated after long-term illumination by the boron-oxygen recombination centre. To allow accurate modelling of upgraded-metallurgical silicon solar cells, we propose a parameterization of these fundamental properties of compensated silicon. We study the light-induced lifetime degradation in p-type and n-type Si with a wide range of dopant concentrations and compensation levels and show that the boron-oxygen defect is a grown-in complex involving substitutional boron and is rendered electrically active upon injection of carriers through a charge-driven reconfiguration of the defect. Finally, we apply gallium co-doping to the crystallization of upgraded-metallurgical silicon and demonstrate that it allows to significantly increase the tolerance to phosphorus without compromising neither the ingot yield nor the solar cells performance before light-induced degradation.

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Forster, Maxime. "Compensation engineering for silicon solar cells." Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00876318.

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This thesis focuses on the effects of dopant compensation on the electrical properties of crystalline silicon relevant to the operation of solar cells. We show that the control of the net dopant density, which is essential to the fabrication of high-efficiency solar cells, is very challenging in ingots crystallized with silicon feedstock containing both boron and phosphorus such as upgraded metallurgical-grade silicon. This is because of the strong segregation of phosphorus which induces large net dopant density variations along directionally solidified silicon crystals. To overcome this issue, we propose to use gallium co-doping during crystallization, and demonstrate its potential to control the net dopant density along p-type and n-type silicon ingots grown with silicon containing boron and phosphorus. The characteristics of the resulting highly-compensated material are identified to be: a strong impact of incomplete ionization of dopants on the majority carrier density, an important reduction of the mobility compared to theoretical models and a recombination lifetime which is determined by the net dopant density and dominated after long-term illumination by the boron-oxygen recombination centre. To allow accurate modelling of upgraded-metallurgical silicon solar cells, we propose a parameterization of these fundamental properties of compensated silicon. We study the light-induced lifetime degradation in p-type and n-type Si with a wide range of dopant concentrations and compensation levels and show that the boron-oxygen defect is a grown-in complex involving substitutional boron and is rendered electrically active upon injection of carriers through a charge-driven reconfiguration of the defect. Finally, we apply gallium co-doping to the crystallization of upgraded-metallurgical silicon and demonstrate that it allows to significantly increase the tolerance to phosphorus without compromising neither the ingot yield nor the solar cells performance before light-induced degradation.

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McCann, Michelle Jane, and michelle mccann@uni-konstanz de. "Aspects of Silicon Solar Cells: Thin-Film Cells and LPCVD Silicon Nitride." The Australian National University. Faculty of Engineering and Information Technology, 2002. http://thesis.anu.edu.au./public/adt-ANU20040903.100315.

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This thesis discusses the growth of thin-film silicon layers suitable for solar cells using liquid phase epitaxy and the behaviour of oxide LPCVD silicon nitride stacks on silicon in a high temperature ambient.¶ The work on thin film cells is focussed on the characteristics of layers grown using liquid phase epitaxy. The morphology resulting from different seeding patterns, the transfer of dislocations to the epitaxial layer and the lifetime of layers grown using oxide compared with carbonised photoresist barrier layers are discussed. The second half of this work discusses boron doping of epitaxial layers. Simultaneous layer growth and boron doping is demonstrated, and shown to produce a 35um thick layer with a back surface field approximately 3.5um thick.¶ If an oxide/nitride stack is formed in the early stages of cell processing, then characteristics of the nitride may enable increased processing flexibility and hence the realisation of novel cell structures. An oxide/nitride stack on silicon also behaves as a good anti- reflection coating. The effects of a nitride deposited using low pressure chemical vapour deposition on the underlying wafer are discussed. With a thin oxide layer between the silicon and the silicon nitride, deposition is shown not to significantly alter effective life-times.¶ Heating an oxide/nitride stack on silicon is shown to result in a large drop in effective Lifetimes. As long as at least a thin oxide is present, it is shown that a high temperature nitrogen anneal results in a reduction in surface passivation, but does not significantly affect bulk lifetime. The reduction in surface passivation is shown to be due to a loss of hydrogen from the silicon/silicon oxide interface and is characterised by an increase in Joe. Higher temperatures, thinner oxides, thinner nitrides and longer anneal times are all shown to result in high Joe values. A hydrogen loss model is introduced to explain the observations.¶ Various methods of hydrogen re-introduction and hence Joe recovery are then discussed with an emphasis on high temperature forming gas anneals. The time necessary for successful Joe recovery is shown to be primarily dependent on the nitride thickness and on the temperature of the nitrogen anneal. With a high temperature forming gas anneal, Joe recovery after nitrogen anneals at both 900 and 1000oC and with an optimised anti-reflection coating is demonstrated for chemically polished wafers.¶ Finally the effects of oxide/nitride stacks and high temperature anneals in both nitrogen and forming gas are discussed for a variety of wafers. The optimal emitter sheet resistance is shown to be independent of nitrogen anneal temperature. With textured wafers, recovery of Joe values after a high temperature nitrogen anneal is demonstrated for wafers with a thick oxide, but not for wafers with a thin oxide. This is shown to be due to a lack of surface passivation at the silicon/oxide interface.

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Chen, Wan Lam Florence Photovoltaics &amp Renewable Energy Engineering Faculty of Engineering UNSW. "PECVD silicon nitride for n-type silicon solar cells." Publisher:University of New South Wales. Photovoltaics & Renewable Energy Engineering, 2008. http://handle.unsw.edu.au/1959.4/41277.

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The cost of crystalline silicon solar cells must be reduced in order for photovoltaics to be widely accepted as an economically viable means of electricity generation and be used on a larger scale across the world. There are several ways to achieve cost reduction, such as using thinner silicon substrates, lowering the thermal budget of the processes, and improving the efficiency of solar cells. This thesis examines the use of plasma enhanced chemical vapour deposited silicon nitride to address the criteria of cost reduction for n-type crystalline silicon solar cells. It focuses on the surface passivation quality of silicon nitride on n-type silicon, and injection-level dependent lifetime data is used extensively in this thesis to evaluate the surface passivation quality of the silicon nitride films. The thesis covers several aspects, spanning from characterisation and modelling, to process development, to device integration. The thesis begins with a review on the advantages of using n-type silicon for solar cells applications, with some recent efficiency results on n-type silicon solar cells and a review on various interdigitated backside contact structures, and key results of surface passivation for n-type silicon solar cells. It then presents an analysis of the influence of various parasitic effects on lifetime data, highlighting how these parasitic effects could affect the results of experiments that use lifetime data extensively. A plasma enhanced chemical vapour deposition process for depositing silicon nitride films is developed to passivate both diffused and non-diffused surfaces for n-type silicon solar cells application. Photoluminescence imaging, lifetime measurements, and optical microscopy are used to assess the quality of the silicon nitride films. An open circuit voltage of 719 mV is measured on an n-type, 1 Ω.cm, FZ, voltage test structure that has direct passivation by silicon nitride. Dark saturation current densities of 5 to 15 fA/cm2 are achieved on SiN-passivated boron emitters that have sheet resistances ranging from 60 to 240 Ω/□ after thermal annealing. Using the process developed, a more profound study on surface passivation by silicon nitride is conducted, where the relationship between the surface passivation quality and the film composition is investigated. It is demonstrated that the silicon-nitrogen bond density is an important parameter to achieve good surface pas-sivation and thermal stability. With the developed process and deeper understanding on the surface passivation of silicon nitride, attempts of integrating the process into the fab-rication of all-SiN passivated n-type IBC solar cells and laser doped n-type IBC solar cells are presented. Some of the limitations, inter-relationships, requirements, and challenges of novel integration of SiN into these solar cell devices are identified. Finally, a novel metallisation scheme that takes advantages of the different etching and electroless plating properties of different PECVD SiN films is described, and a preliminary evalua-tion is presented. This metallisation scheme increases the metal finger width without increasing the metal contact area with the underlying silicon, and also enables optimal distance between point contacts for point contact solar cells. It is concluded in this thesis that plasma enhanced chemical vapour deposited silicon nitride is well-suited for n-type silicon solar cells.

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Slade, Alexander Mason Electrical Engineering UNSW. "Boron tribromide sourced boron diffusions for silicon solar cells." Awarded by:University of New South Wales. Electrical Engineering, 2005. http://handle.unsw.edu.au/1959.4/21850.

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This thesis undertakes the development, characterization and optimization of boron diffusion for silicon solar cells. Heavy diffusions (sheet resistance < 40 Ohm/square) to form a back surface field, and light diffusions (sheet resistance > 100 Ohm/square) to form oxide-passivated emitters were developed. Test structures and solar cells were fabricated to assess uniformity, lifetime and recombination effects due to the light and heavy boron diffusions. It was found that the growth of a thin ~200 ??, thermal oxide, during stabilization ??? immediately prior to the boron diffusion - was required to maintain high lifetime and reduce surface recombination (reducing the emitter saturation current density) for all boron diffusions. The heavy boron diffusion process was incorporated into the single side buried contact solar cell processing sequence. The solar cells fabricated had both boron diffused and Al/Si alloyed P+ regions for comparison. This research conclusively showed that boron diffused solar cells had significantly higher open circuit voltage compared to Al/Si alloyed devices. Fabrication of n-type solar cells, and their subsequent characterization by overlayed secondary electron image and the electron beam induced current map showed that the Al/Si alloy varied in depth from 5 to 25 micrometers deep. Methodology and characterization for light, oxide-passivated boron diffusions are also presented. This study yielded boron diffused emitters (sheet resistance > 100 Ohm/square) with low emitter saturation current. It was observed that this was possible only when the thermal oxidation after the boron diffusion was minimal, less than 1,000 ??. This was due to the segregation effect of boron with oxide, decreasing the surface concentration that in turn decreased the electric field repulsion of electrons from the surface. Device modelling of n-type solar cells is presented where the parameters of the modelling include the results of the light, oxide-passivated boron diffusions. This modelling shows n-type-base material with light oxide-passivated boron diffusion has higher potential conversion efficiency than forming a solar cell from phosphorous diffused p-type material.

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Kaminski, Piotr M. "Remote plasma sputtering for silicon solar cells." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13058.

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The global energy market is continuously changing due to changes in demand and fuel availability. Amongst the technologies considered as capable of fulfilling these future energy requirements, Photovoltaics (PV) are one of the most promising. Currently the majority of the PV market is fulfilled by crystalline Silicon (c-Si) solar cell technology, the so called 1st generation PV. Although c-Si technology is well established there is still a lot to be done to fully exploit its potential. The cost of the devices, and their efficiencies, must be improved to allow PV to become the energy source of the future. The surface of the c-Si device is one of the most important parts of the solar cell as the surface defines the electrical and the optical properties of the device. The surface is responsible for light reflection and charge carrier recombination. The standard surface finish is a thin film layer of silicon nitride deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD). In this thesis an alternative technique of coating preparation is presented. The HiTUS sputtering tool, utilising a remote plasma source, was used to deposit the surface coating. The remote plasma source is unique for solar cells application. Sputtering is a versatile process allowing growth of different films by simply changing the target and/or the deposition atmosphere. Apart from silicon nitride, alternative materials to it were also investigated including: aluminium nitride (this was the first use of the material in solar cells) silicon carbide, and silicon carbonitride. All the materials were successfully used to prepare solar cells apart from the silicon carbide, which was not used due to too high a refractive index. Screen printed solar cells with a silicon nitride coating deposited in HiTUS were prepared with an efficiency of 15.14%. The coating was deposited without the use of silane, a hazardous precursor used in the PECVD process, and without substrate heating. The elimination of both offers potential processing advantages. By applying substrate heating it was found possible to improve the surface passivation and thus improve the spectral response of the solar cell for short wavelengths. These results show that HiTUS can deposit good quality ARC for silicon solar cells. It offers optical improvement of the ARC s properties, compared to an industrial standard, by using the DL-ARC high/low refractive index coating. This coating, unlike the silicon nitride silica stack, is applicable to encapsulated cells. The surface passivation levels obtained allowed a good blue current response.

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Madhavan, Atul. "Alternative designs for nanocrystalline silicon solar cells." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3403005.

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Nordmark, Heidi. "Microstructure studies of silicon for solar cells." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5384.

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Reuter, Michael [Verfasser]. "Thin Crystalline Silicon Solar Cells / Michael Reuter." München : Verlag Dr. Hut, 2011. http://d-nb.info/1012432041/34.

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Inns, Daniel Photovoltaics &amp Renewable Energy Engineering Faculty of Engineering UNSW. "ALICIA polycrystalline silicon thin-film solar cells." Publisher:University of New South Wales. Photovoltaics & Renewable Energy Engineering, 2007. http://handle.unsw.edu.au/1959.4/43600.

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Thin-film silicon photovoltaics are seen as a good possibility for reducing the cost of solar electricity. The focus of this thesis is the ALICIA cell, a thin-film polycrystalline silicon solar cell made on a glass superstrate. The name ALICIA comes from the fabrication steps - ALuminium Induced Crystallisation, Ion Assisted deposition. The concept is to form a high-quality crystalline silicon layer on glass by Aluminium Induced Crystallisation (AIC). This is then the template from which to epitaxially grow the solar cell structure by Ion Assisted Deposition (IAD). IAD allows high-rate silicon epitaxy at low temperatures compatible with glass. In thin-film solar cells, light trapping is critical to increase the absorption of the solar spectrum. ALICIA cells have been fabricated on textured glass sheets, increasing light absorption due to their anti-reflection nature and light trapping properties. A 1.8 μm thick textured ALICIA cell absorbs 55% of the AM1.5G spectrum without a back-surface reflector, or 76% with an optimal reflector. Experimentally, Pigmented Diffuse Reflectors (PDRs) have been shown to be the best reflector. These highly reflective and optically diffuse materials increase the light-trapping potential and hence the short-circuit currents of ALICIA cells. In textured cells, the current increased by almost 30% compared to using a simple aluminium reflector. Current densities up to 13.7 mA/cm2 were achieved by application of a PDR to the best ALICIA cells. The electronic quality of the absorber layer of ALICIA cells is strongly determined by the epitaxy process. Very high-rate epitaxial growth decreases the crystalline quality of the epitaxial layer, but nevertheless increases the short-circuit current density of the solar cells. This indicates that the diffusion length in the absorber layer of the ALICIA cell is primarily limited by contamination, not crystal quality. Further gains in current density can therefore be achieved by increasing the deposition rate of the absorber layer, or by improving the vacuum quality. Large-area ALICIA cells were then fabricated, and series resistance reduced by using an interdigitated metallisation scheme. The best measured efficiency was 2.65%, with considerable efficiency gains still possible from optimisation of the epitaxial growth and metallisation processes.

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Stüwe, David [Verfasser], and Jan G. [Akademischer Betreuer] Korvink. "Inkjet processes for crystalline silicon solar cells." Freiburg : Universität, 2015. http://d-nb.info/1122646984/34.

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Shariff, A. "Computer simulation of amorphous silicon solar cells." Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638814.

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A detailed numerical model of the electronic properties of hydrogenated amorphous silicon has been developed and shown to be a useful tool for the analysis of the performance and optimization of the design of solar cells. The method of simulation involves solving Poissons's equation, and the electron and hole continuity equations, in conjunction with the transport equations for the electrons and holes. From the solutions of these equations we obtained the electrostatic potential, the electron and hole concentrations and the current densities. A set of realistic material parameters has been used. We have modelled the density of states to consist of two exponential band tails and the dangling bonds. Recombination in both the band tails and the dangling bonds has been taken into consideration in the model. We investigated the effect of the cell performance on varying dangling bond densities (1016cm-3-1017cm-3) for various cell thicknesses of p-i-n hydrogenated amorphous silicon solar cells, for incident blue and red light. Our results agree well with experiments for solar cells in the undegraded state. However for the degraded state the fill factors appear to be higher than the experimental values. This might be because we have only assumed a single level dangling bond density in our model. It is suggested that future work might undertake the incorporation of the spatial dependence of the dangling bond density in the model.

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Tsuda, Shinya. "TOWARDS HIGH EFFICIENCY AMORPHOUS SILICON SOLAR CELLS." Kyoto University, 1988. http://hdl.handle.net/2433/162221.

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Davidson, Lauren Michel. "Strategies for high efficiency silicon solar cells." Thesis, University of Iowa, 2017. https://ir.uiowa.edu/etd/5452.

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The fabrication of low cost, high efficiency solar cells is imperative in competing with existing energy technologies. Many research groups have explored using III-V materials and thin-film technologies to create high efficiency cells; however, the materials and manufacturing processes are very costly as compared to monocrystalline silicon (Si) solar cells. Since commercial Si solar cells typically have efficiencies in the range of 17-19%, techniques such as surface texturing, depositing a surface-passivating film, and creating multi-junction Si cells are used to improve the efficiency without significantly increasing the manufacturing costs. This research focused on two of these techniques: (1) a tandem junction solar cell comprised of a thin-film perovskite top cell and a wafer-based Si bottom cell, and (2) Si solar cells with single- and double-layer silicon nitride (SiNx) anti-reflection coatings (ARC). The perovskite/Si tandem junction cell was modeled using a Matlab analytical program. The model took in material properties such as doping concentrations, diffusion coefficients, and band gap energy and calculated the photocurrents, voltages, and efficiencies of the cells individually and in the tandem configuration. A planar Si bottom cell, a cell with a SiNx coating, or a nanostructured black silicon (bSi) cell can be modeled in either an n-terminal or series-connected configuration with the perovskite top cell. By optimizing the bottom and top cell parameters, a tandem cell with an efficiency of 31.78% was reached. Next, planar Si solar cells were fabricated, and the effects of single- and double-layer SiNx films deposited on the cells were explored. Silicon nitride was sputtered onto planar Si samples, and the refractive index and thicknesses of the films were measured using ellipsometry. A range of refractive indices can be reached by adjusting the gas flow rate ratios of nitrogen (N2) and argon (Ar) in the system. The refractive index and thickness of the film affect where the minimum of the reflection curve is located. For Si, the optimum refractive index of a single-layer passivation film is 1.85 with a thickness of 80nm so that the minimum reflection is at 600nm, which is where the photon flux is maximized. However, using a double-layer film of SiNx, the Si solar cell performance is further improved due to surface passivation and lowered surface reflectivity. A bottom layer film with a higher refractive index passivates the Si cell and reduces surface reflectivity, while the top layer film with a smaller refractive index further reduces the surface reflectivity. The refractive indices and thicknesses of the double-layer films were varied, and current-voltage (IV) and external quantum efficiency (EQE) measurements were taken. The double-layer films resulted in an absolute value increase in efficiency of up to 1.8%.

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Cai, Li. "Improved understanding and control of the properties of PECVD silicon nitride and its applications in multicrystalline silicon solar cells." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/15468.

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Schumacher, Jürgen Otto. "Numerical simulation of silicon solar cells with novel cell structures." [S.l. : s.n.], 2000. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9170598.

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Lu, Meijun. "Silicon heterojunction solar cell and crystallization of amorphous silicon." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 295 p, 2009. http://proquest.umi.com/pqdweb?did=1654494651&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Brody, Jed. "Doping dependence of surface and bulk passivation of multicrystalline silicon solar cells." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180041/unrestricted/brody%5Fjed%5F200312%5Fphd.pdf.

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Jain, Nikhil. "Design of III-V Multijunction Solar Cells on Silicon Substrate." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/33048.

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With looming energy crisis across the globe, achieving high efficiency and low cost solar cells have long been the key objective for photovoltaic researchers. III-V compound semiconductor based multijunction solar cells have been the dominant choice for space power due to their superior performance compared to any other existing solar cell technologies. In spite of unmatched performance of III-V solar cells, Si cells have dominated the terrestrial market due to their lower cost. Most of the current III-V solar cells are grown on Ge or GaAs substrates, which are not only smaller in diameter, but are also more expensive than Si substrate. Direct integration of high efficiency III-V solar cells on larger diameter, cheaper and readily available Si substrate is highly desirable for increased density, low-cost and lightweight photovoltaics. However, the polar-on-nonpolar epitaxy, the thermal mismatch and the 4% lattice mismatch makes the direct growth of GaAs on Si challenging, rendering the metamorphic cell sensitive to dislocations. The focus of this work is to investigate and correlate the impact of threading dislocation density on the performance of lattice-mismatched single-junction (1J) GaAs and dual-junction (2J) InGaP/GaAs solar cells on Si substrate. Utilizing our calibrated dislocation-assisted modeling process, we present the design methodology to optimize the structure of 2J InGaP/GaAs solar cell on Si substrate. Our modeling results suggest an optimistic future for integrating III-V solar cell technology on Si substrate and will be useful for future design and prediction of metamorphic III-V solar cell performance on Si substrate. Master of Science

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Yao, Guoxiao Centre for Photovoltaic Engineering UNSW. "High efficiency metal stencil printed silicon solar cells." Awarded by:University of New South Wales. Centre for Photovoltaic Engineering, 2005. http://handle.unsw.edu.au/1959.4/23062.

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This thesis work demonstrates the feasibility to fabricate high-efficiency crystalline silicon solar cells by using metal stencil printing technique to replace screen printing or electroless plating techniques for implementing crystalline silicon solar cell front metallization. The developed laser-cut stainless steel stencils successfully challenge two of the cell performance limitations associated with commercial screen printing technology: the wide and non-uniform front gridline fingers and low height-to-width aspect ratio of the fingers. These limitations lower the short circuit current density, the fill factor and, in turn, the efficiency of a screen printed solar cell. Metal stencils are capable of printing fine, high and continuous features on the cell front that have a high aspect ratio. Both single-level and double-level structured stainless steel stencils for solar cell front metallization have been developed, with laser-cut double-level stainless steel stencils being demonstrated for the first time worldwide. Both of them are able to print fine, high and continuous gridline pattern to the front surfaces of solar cells in one step, with a certain number of special short bridges being put at the places where fingers meet busbar and along fingers and busbar. The deformation issue of the very thin stainless steel foils due to its thermal expansion in the process of laser cutting is solved by increasing the energy content in each laser pulse that impinges upon the stainless steel foil with changed Q-switch frequencies, while maintaining the laser average output energy in unit time to an optimum value. A chemical etching process has been developed to etch the dross that results from laser cutting, resulting in well formed metal stencils suitable for printing. By a comparison between the metal stencil printed and conventional mesh screen printed silicon solar cells, which are fabricated on similar Cz silicon wafers with a almost identical cell processing sequence except for using different front contact printing masks, the following conclusions are reached: Fired Ag finger lines with 75-??m width on finished solar cells, using a doublelevel stainless steel stencil can be achieved. In contrast, the fired Ag finger line on finished solar cells using a traditional mesh screen is 121-??m wide. The stencil printed finger is smoother and more uniform than by screen printing and the former has a 25-??m fired finger height with a 0.33 height-to-width aspect ratio, compared to a 10-??m fired finger height with a 0.08 height-to-width aspect ratio for the later. With these advantages, the 4-cm2 stencil-printed silicon solar cells has an averaged 1.28 mA/cm2 higher short circuit current and an averaged 5.9% higher efficiency than the 4-cm2 screen printed silicon solar cell, which identifies one of the key advantages of solar cell metallization schemes by using metal stencil printing in place of screen printing. Using a ???feedback alignment??? method for registration of the laser-formed metal stencil printed pattern and the laser-formed groove pattern, Ag paste can be printed and filled into wafer grooves by using a hand-operated without an optical vision system. The fired finger profile is 50-??m wide and 22-??m high. The best metal stencil printed, selective emitter silicon solar cell demonstrates a 34.2 mA/cm2 short circuit current density, 625 mV open circuit voltage, 0.77 fill factor and 16.4% efficiency, with an excellent spectral response at short wavelengths due to its selective emitter cell structure. It is believed that the performance of this type of solar cell can be enhanced with a screen printer that has an optical vision system and an automatic alignment device. The successful development of metal stencil printed silicon solar cells demonstrates the feasibility of the metal stencil printing as a beneficial technology for the PV industry.

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Ghosh, Kunal. "Modeling of amorphous silicon/crystalline silicon heterojunction by commercial simulator." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 48 p, 2009. http://proquest.umi.com/pqdweb?did=1654493871&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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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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Demircioglu, Olgu. "Optimization Of Metalization In Crystalline Silicon Solar Cells." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614584/index.pdf.

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iv ABSTRACT OPTIMIZATION OF METALIZATION IN CRYSTALLINE SILICON SOLAR CELLS Demircioglu, Olgu M. Sc. Department of Micro and Nanotechnology Supervisor : Prof. Dr. Rasit Turan Co-Supervisor : Assist. Prof. Dr. H. Emrah &Uuml nalan August 2012, 103 pages Production steps of crystalline silicon solar cells include several physical and chemical processes like etching, doping, annealing, nitride coating, metallization and firing of the metal contacts. Among these processes, the metallization plays a crucial role in the energy conversion performance of the cell. The quality of the metal layers used on the back and the front surface of the cell and the quality of the electrical contact they form with the underlying substrate have a detrimental effect on the amount of the power generated by the cell. All aspects of the metal layer, such as electrical resistivity, contact resistance, thickness, height and width of the finger layers need to be optimized very carefully for a successful solar cell operation. In this thesis, metallization steps within the crystalline silicon solar cell production were studied in the laboratories of Center for Solar Energy Research and Application (G&Uuml NAM). Screen Printing method, which is the most common metallization technique in the industry, was used for the metal layer formation. With the exception of the initial experiments, 6

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Macdonald, Daniel Harold, and daniel@faceng anu edu au. "Recombination and Trapping in Multicrystalline Silicon Solar Cells." The Australian National University. Faculty of Engineering and Information Technology, 2001. http://thesis.anu.edu.au./public/adt-ANU20011218.134830.

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In broad terms, this thesis is concerned with the measurement and interpretation of carrier lifetimes in multicrystalline silicon. An understanding of these lifetimes in turn leads to a clearer picture of the limiting mechanisms in solar cells made with this promising material, and points to possible paths for improvement. The work falls into three broad categories: gettering, trapping and recombination. A further section discusses a powerful new technique for characterising impurities in semiconductors in general, and provides an example of its application. Gettering of recombination centres in multicrystalline silicon wafers improves the bulk lifetime, often considerably. Although not employed deliberately in most commercial cell processes, gettering nevertheless occurs to some extent during emitter formation, and so may have an important impact on cell performance. However, the response of different wafers to gettering is quite variable, and in some cases is non-existent. Work in this thesis shows that the response to gettering is best when the dislocation density is low and the density of mobile impurities is high. For Eurosolare material these conditions prevail at the bottom and to a lesser extent in the middle of an ingot. However, these conclusions can not always be applied to multicrystalline silicon produced by other manufacturers. Low resistivity multicrystalline silicon suffers from a concurrent thermally induced degradation of the lifetime. This had previously been attributed to the dissolution of precipitated metals, although we note that the crystallographic quality also appears to deteriorate. The thermal degradation effect results in an optimum gettering time for low resistivity material. Edge-defined Film-fed Growth (EFG) ribbon silicon was also found to respond to gettering, and even more so to bulk hydrogenation. Evidence for Cu contamination in the as-grown EFG wafers is presented. Multicrystalline silicon is often plagued by trapping effects, which can make lifetime measurement in the injection-level range of interest very difficult, and sometimes impossible. An old model based on centres that trap and release minority carriers, but do not interact with majority carriers, was found to provide a good explanation for these effects. These trapping states were linked with the presence of dislocations and also with boron-impurity complexes. Their annealing behaviour and lack of impact on device parameters can be explained in terms of the models developed. The trapping model allowed a recently proposed method for correcting trap-affected data to be tested using typical values of the trapping parameters. The correction method was found to extend the range of useable data to approximately an order of magnitude lower in terms of carrier density than would be available otherwise, an improvement that could prove useful in many practical cases. High efficiency PERL and PERC cells made on gettered multicrystalline silicon resulted in devices with open circuit voltages in the 640mV range that were almost entirely limited by bulk recombination. Furthermore, the injection-level dependence of the bulk lifetime resulted in decreased fill factors. Modelling showed that these effects are even more pronounced for cells dominated by interstitial iron recombination centres. Analysis of a commercial multicrystalline cell fabrication process revealed that recombination in the emitter created the most stringent limit on the open circuit voltage, followed by the bulk and the rear surface. The fill factors of these commercial cells were mostly affected by series resistance, although some reduction due to injection-level dependent lifetimes seems likely also. Secondary Ion Mass Spectroscopy on gettered layers of multicrystalline silicon revealed the presence of Cr and Fe in considerable quantities. Further evidence strongly implied that they resided almost exclusively as precipitates. More generally, injection-level dependent lifetime measurements offer the prospect of powerful contamination-monitoring tools, provided that the impurities are well characterised in terms of their energy levels and capture cross-sections. Conversely, lifetime measurements can assist with this process of characterising impurities, since they are extremely sensitive to their presence. This possibility is explored in this thesis, and a new technique, dubbed Injection-level Dependent Lifetime Spectroscopy (IDLS) is developed. To test its potential, the method was applied to the well-known case of FeB pairs in boron-doped silicon. The results indicate that the technique can offer much greater accuracy than more conventional DLTS methods, and may find applications in microelectronics as well as photovoltaics.

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Song, Yang Photovoltaics &amp Renewable Energy Engineering Faculty of Engineering UNSW. "Dielectric thin film applications for silicon solar cells." Publisher:University of New South Wales. Photovoltaics & Renewable Energy Engineering, 2009. http://handle.unsw.edu.au/1959.4/44486.

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Dielectric thin films have a long history in silicon photovoltaics. Due to the specific physical properties, they can function as passivation layer in solar cells. Also, they can be used as antireflection coating layers on top of the devices. They can improve the back surface reflectance if proper dielectric layers combination is used. What??s more, they can protect areas by masking during chemical etching, diffusion, metallization among the whole fabrication process. Crystalline silicon solar cell can be passivated by two ways: one is to deposit dielectric thin films to saturate the dangling bonds; the other is to introduce surface electrical field and repel back the minority carriers. This thesis explores thermally grown SiO2 and sputtered Si3N4(:H) to passivate n-type and thermal evaporation AlF3 to passivate p-type Float Zone silicon wafers, respectively. Sputtering is a cheap passivation method to replace PECVD in industry usage, but all sputtered samples are more likely to have encountered surface damage from neutral Ar and secondary electrons, both coming from the sputtered target. AlF3/SiO2 multi-layer stack is a negative charge combination; p inversion layer will form on the wafer surface. Light trapping is an important part in solar cell research work. In order to enhance the reflectance and improve the absorption possibility of near infrared photons, especially for high efficiency PERL cell application, the back surface structure is optimized in this work. Results show SiO2/Ag is a very good choice to replace SiO2/Al back reflectors. The maximum back surface reflectance is 97.82%. At the same time, SiO2/Ag has excellent internal angle dependence of reflectance, which is beneficial for surface textured cells. A ZnS/MgF2/SiO2/Al(Ag) superlattice can improve the back reflectance, but it is sensitive to incident angle inside the silicon wafer. If planar wafers are used to investigate all kinds of back reflectors, and an 8 degrees incident angle is fixed for typical spectrometry measurement, the results are easy to predict by Wvase software simulation. If a textured surface is considered, the light path inside the silicon wafer is very complicated and hard to calculate and simulate. The best way to evaluate the result is through experiment.

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Liang, Jianjun. "Device physics of hydrogenated amorphous silicon solar cells." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2006. http://proquest.umi.com/login?COPT=REJTPTU0NWQmSU5UPTAmVkVSPTI=&clientId=3739.

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Jamshidi, Gohari Ebrahim. "Buried screen-printed contacts for silicon solar cells." Thesis, Högskolan Dalarna, Energi och miljöteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:du-13593.

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A Simple way to improve solar cell efficiency is to enhance the absorption of light and reduce the shading losses. One of the main objectives for the photovoltaic roadmap is the reduction of metalized area on the front side of solar cell by fin lines. Industrial solar cell production uses screen-printing of metal pastes with a limit in line width of 70-80 μm. This paper will show a combination of the technique of laser grooved buried contact (LGBC) and Screen-printing is able to improve in fine lines and higher aspect ratio. Laser grooving is a technique to bury the contact into the surface of silicon wafer. Metallization is normally done with electroless or electrolytic plating method, which a high cost. To decrease the relative cost, more complex manufacturing process was needed, therefore in this project the standard process of buried contact solar cells has been optimized in order to gain a laser grooved buried contact solar cell concept with less processing steps. The laser scribing process is set at the first step on raw mono-crystalline silicon wafer. And then the texturing etch; phosphorus diffusion and SiNx passivation process was needed once. While simultaneously optimizing the laser scribing process did to get better results on screen-printing process with fewer difficulties to fill the laser groove. This project has been done to make the whole production of buried contact solar cell with fewer steps and could present a cost effective opportunity to solar cell industries. In collaboration with Institute for Photovoltaics IPV, University of Stuttgart.

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Heß, Uwe [Verfasser]. "Investigations of RGS Silicon Solar Cells / Uwe Heß." München : Verlag Dr. Hut, 2013. http://d-nb.info/1037286839/34.

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Shih, Jeanne-Louise. "Zinc oxide-silicon heterojunction solar cells by sputtering." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112583.

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Heterojunctions of n-ZnO/p-Si solar cells were fabricated by RF sputtering ZnO:Al onto boron-doped (100) silicon (Si) substrates. Zinc Oxide (ZnO) films were also deposited onto soda lime glass for electrical measurements. Sheet resistance measurements were performed with a four-point-probe on the glass samples. Values for samples evacuated for 14 hours prior to deposition increased from 7.9 to 10.17 and 11.5 O/&squ; for 40 W, 120 and 160 W in RF power respectively. In contrast, those evacuated for 2 hours started with a higher value of 22.5 O/&squ;, and decreased down to 7.6 and 5.8 O/&squ;. Vacuum annealing was performed for both the glass and the Si samples. Current-voltage measurements were performed on the ZnO/Si junctions in the dark and under illumination. Parameters such as open-circuit voltage, Voc; short-circuit current, Isc; fill factor, FF; and efficiency, eta were determined. A maximum efficiency of 0.25% among all samples was produced, with an I sc of 2.16 mA, Voc of 0.31V and a FF of 0.37. This was a sample fabricated at an RF power of 80 W. Efficiency was found to decline with vacuum annealing. Furthermore, interfacial state density calculated based on capacitance-voltage measurements showed an increase in the value with vacuum annealing. The results found suggest that the interface states may be due to an interdiffusion of atoms, possibly those of Zn into the Si surface. The Electron Beam Induced Current (EBIC) method was used to determine diffusion length to be at a value &sim;40--80 mum and therefore a minority carrier lifetime calculated of 3 musec. It was also used to determine the surface recombination velocity (SRV) of the fractured surface of the Si bulk from the fabricated solar cells. An SRV of &sim;500 cm/sec was determined from the fractured Si surface, at a point located at 30 and 20 mum away from the junction interface.

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Tucher, Nico [Verfasser], Claas [Verfasser] Müller, and Stefan [Verfasser] Glunz. "Analysis of photonic structures for silicon solar cells." Freiburg : Universität, 2016. http://d-nb.info/1136567186/34.

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40

Thomas, Trevor. "The computer modelling of amorphous silicon solar cells." Thesis, Cardiff University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361326.

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41

Thompson, Robin Forster. "Doping effects in hydrogenated amorphous silicon solar cells." Thesis, Heriot-Watt University, 1985. http://hdl.handle.net/10399/1624.

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Mahanama, G. D. K. "Low temperature processing of crystalline silicon solar cells." Thesis, London South Bank University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435235.

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Tahhan, Abdulla. "Energy performance enhancement of crystalline silicon solar cells." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/14503.

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The work in this thesis examines the effects of the application of oxide coatings on the performance of the single crystalline silicon photovoltaic solar cells. A variety of potential oxide materials for solar cells performance enhancement are investigated. These films are silicon oxide, titanium oxide and rare earth ion-doped gadolinium oxysulfide phosphor. This study compares the electrical characteristics, optical properties and surface chemical composition of mono-crystalline silicon cells before and after coating. The first study investigates the potential for using single and double layers of silicon oxide films produced by low-temperature Plasma Enhanced Chemical Vapour Deposition (PECVD) using tetramethylsilane as a silicon precursor and potassium permanganate oxidising agent for efficiency enhancement of solar cells at low manufacturing cost. Deposition of the films contributes to the increase of the conversion energy of the solar cells on one hand while the variety of colours obtained in this study can be of great importance for building-integrated photovoltaic application on the other hand. The obtained results demonstrated a relative enhancement of 3% in the conversion efficiency of the crystalline silicon solar cell. In the second study, the effects of using a single layer of titanium oxide and a stack of silicon oxide and titanium oxide on the performance of solar cell are demonstrated. Moreover, this study shows the use of different sputtering configurations and oxidation methods. The experimental results showed a relative enhancement of 1.6% for solar cells coated with a stack of silicon oxide/titanium oxide. In the third study, silicon cells were coated with a luminescent layer consisting of down-converting phosphor, gadolinium oxysulfide doped with erbium and terbium, and a polymeric binder of EVA using doctor-blade screen printing technique. A relative enhancement of 4.45% in the energy conversion efficiency of PV solar cell was achieved. Also, the effects of combining silicon oxide layers together with the luminescent composite are also presented in this study.

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Ball, Jeremy. "The growth of silicon nanowires for solar cells." Thesis, London South Bank University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.587543.

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At present silicon wafer technologies dominate the market place with cost driven by the technological requirement for optically thick and electronically pure silicon. A solution to the high cost of wafer based panels is a thin film approach where micron thick layers of silicon replace the ~250 micron thick silicon wafers. Thin film silicon has gone to market in the form of amorphous and microcrystalline Si where performance is an issue as well as stability due to the hydrogenated amorphous Si structure. This project involves the growth of three dimensional wire structures based on crystalline silicon and their integration into solar cell devices. Nanowire solar cells featuring a radial junction have the potential to reduce the required volume and purity of the silicon used in cell fabrication compared to wafer based technologies. The vapour-liquid-solid effect (VLS) has been used to grow Si nanowires using Au and Sn as catalyst metals together with electron cyclotron resonance chemical vapour deposition (ECRCVD) for silicon deposition. Experimental results include the formation of seed particles from both gold and tin catalyst layers leading to the growth of silicon nanowires on both silicon wafer and glass substrates. The study of nanowire growth parameters from both gold and tin catalysts has led to the proposal of a model for growth in a low pressure environment as found in ECRCVD. Structural characterisation of the wires has taken place. Wires grown from gold catalyst layers on silicon are single crystal where the growth direction has a clear dependence on the orientation of the substrate. Those from tin exhibit a nanocrystalline shell over a single crystal core and have a tapered morphology. Furthermore, the growth direction is independent of substrate orientation. Reasons for this are discussed. Optical characterisation of the nanowire arrays has revealed high levels of broadband absorption. These results have been compared with finite difference time domain modelling (FDTD) and conclusions on the effects of wire density and catalyst layer thickness, along with that of the underlying silicon layer, have been drawn. The implication of these results for the design of solar cells based on these wires is discussed. Simple solar cell devices have been fabricated demonstrating photovoltaic response but with limited performance. The reasons for this are discussed with areas for improvement.

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Quinn, Thomas Edward. "Growth and crystallisation of silicon for solar cells." Thesis, London South Bank University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.570870.

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Polycrystalline silicon seed layer formation by aluminium-induced crystallisation (AIC) for solar cell applications was investigated. Precursor amorphous and microcrystalline silicon layers were deposited on SiO2 substrates using electron-cyclotron resonance plasma-enhanced chemical vapour deposition (ECR PECVD) and RF sputter deposition followed by thermal evaporation or RF sputter deposition of aluminium layers. Samples were then thermally annealed leading to layer exchange and crystallisation of the silicon layer. Selected samples were used as seed layers for ECR PECVD epitaxial thickening. Processing was usually done at temperatures less than 600°C compatible with glass substrates. Deposition parameters (substrate temperature, deposition time, gas flow rates, chamber pressure and magnetic currents) for ECR PECVD Si growth using SiH4 and H2 on bare and oxidised silicon wafers were varied to examine the effect on the crystallinity of deposited layers. This was related to properties of the plasma using diagnostic measurements. A method of adding argon to the chamber, found to be beneficial to material properties of deposited films, without causing the often observed reduction in growth rates was found. A study was then undertaken to optimise growth conditions of precursor silicon and aluminium layers for suitable seed layers by AIC. Using ECR PECVD deposited silicon and evaporated aluminium was found to lead to continuous layers after short annealing time, sometimes less than 15min, than using sputtered aluminium or silicon precursor layers which did not form continuous layers after several hours of annealing at 500°C. Using thin microcrystalline silicon was also found to lead to better film quality after annealing than thicker amorphous silicon films. Increasing the temperature during AIC from 250°C to 475°C was found to reduce the annealing time to typically 30 minutes at the highest temperature while allowing relatively large grains of several microns to form. Growth of a thick Si-Al interfacial oxide also lead to larger grain sizes. Under optimal preparation and annealing conditions, i.e. ECR PECVD μc-Si growth conditions and an annealing temperature of around 400°C, AIC produced continuous polycrystalline silicon seed layers with large grains up to 100μm, a preferential (001) orientation and a relatively smooth surface morphology with Ra values typically in the range of 20-30nm. Improvements in surface morphology and crystallinity were seen after subjecting AIC polycrystalline silicon to excimer laser irradiation at optimal fluence. Based on the above results and previous published work the process of AIC is discussed. ECR PECVD overgrowth on AIC seed layers was found to be epitaxial but the crystalline quality diminishes with thickness. Adding argon during deposition was found to be beneficial in producing thick, epitaxially grown layers with 2.5μm thick epitaxial layers achieved.

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Schuster, Christian. "Diffractive optics for thin-film silicon solar cells." Thesis, University of York, 2015. http://etheses.whiterose.ac.uk/9083/.

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Thin-film silicon solar cells have the potential to convert sunlight into electricity at high efficiency, low cost and without generating pollutants. However, they need to become more competitive with conventional energy technologies by increasing their efficiency. One of the key efficiency limitations of using thin silicon absorber materials relates to the optical loss of low-energy photons, because the absorption coefficient of silicon decreases strongly for these low-energy photons in the red and near-infrared, such that the absorption length becomes longer than the absorber layer thickness. If, in contrast, the incident light was redirected and trapped into the plane of the silicon slab, a thin-film could absorb as much light as a thick layer. Diffractive textures can not only efficiently scatter the low-energy photons, but are also able to suppress the reflection of the incident sunlight. In order to take advantage of the full benefits that textures can offer, I outline a simple layer transfer technique that allows the structuring of a thin-film independently from both sides, and use absorption measurements to show that structuring on both sides is favourable compared to structuring on one side only. I also introduce a figure-of-merit that can objectively and quantitatively assess the benefit of the structuring itself, which allows me to benchmark state-of-the-art proposals and to deduce some important design rules. Minimising the parasitic losses, for example, is of critical importance, as the desired scattering properties are directly proportional to these losses. To study the impact of parasitics, I quantify the useful absorption enhancement of two different light trapping mechanisms, i.e. diffractive vs plasmonic, based on a fair and simple experimental comparison. The experiment demonstrates that diffractive light-trapping is a better choice for photovoltaic applications, because plasmonic structures accumulate the parasitical losses by multiple interactions with the trapped light. The results of this thesis therefore highlight the importance of diffractive structures as an effective way of trapping more light in a thinner solar cell device, and will help to define guidelines for new designs that may overcome the 30% power conversion efficiency limit.

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Schube, Jörg [Verfasser], and Stefan [Akademischer Betreuer] Glunz. "Metallization of silicon solar cells with passivating contacts." Freiburg : Universität, 2020. http://d-nb.info/1225294142/34.

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48

Zanuccoli, Mauro <1974&gt. "Advanced Numerical Simulation of Silicon-Based Solar Cells." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4566/1/Zanuccoli_Mauro_tesi.pdf.

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Abstract:

Photovoltaic (PV) conversion is the direct production of electrical energy from sun without involving the emission of polluting substances. In order to be competitive with other energy sources, cost of the PV technology must be reduced ensuring adequate conversion efficiencies. These goals have motivated the interest of researchers in investigating advanced designs of crystalline silicon solar (c-Si) cells. Since lowering the cost of PV devices involves the reduction of the volume of semiconductor, an effective light trapping strategy aimed at increasing the photon absorption is required. Modeling of solar cells by electro-optical numerical simulation is helpful to predict the performance of future generations devices exhibiting advanced light-trapping schemes and to provide new and more specific guidelines to industry. The approaches to optical simulation commonly adopted for c-Si solar cells may lead to inaccurate results in case of thin film and nano-stuctured solar cells. On the other hand, rigorous solvers of Maxwell equations are really cpu- and memory-intensive. Recently, in optical simulation of solar cells, the RCWA method has gained relevance, providing a good trade-off between accuracy and computational resources requirement. This thesis is a contribution to the numerical simulation of advanced silicon solar cells by means of a state-of-the-art numerical 2-D/3-D device simulator, that has been successfully applied to the simulation of selective emitter and the rear point contact solar cells, for which the multi-dimensionality of the transport model is required in order to properly account for all physical competing mechanisms. In the second part of the thesis, the optical problems is discussed. Two novel and computationally efficient RCWA implementations for 2-D simulation domains as well as a third RCWA for 3-D structures based on an eigenvalues calculation approach have been presented. The proposed simulators have been validated in terms of accuracy, numerical convergence, computation time and correctness of results. La conversione fotovoltaica è la produzione diretta di energia elettrica dal sole che non comporta l'emissione di sostanze inquinanti. Al fine di competere con altre fonti di energia, la tecnologia fotovoltaica deve subire una riduzione del costo garantendo contemporaneamente adeguate efficienze di conversione. Questi obiettivi hanno motivato l'interesse dei ricercatori al progetto ed all'analisi di celle solari avanzate in silicio cristallino. Poiché la riduzione del costo dei dispositivi fotovoltaici comporta tipicamente la riduzione del volume di semiconduttore, è necessaria una strategia efficace di intrappolamento della luce per aumentare l'assorbimento dei fotoni. Gli approcci orientati alla simulazione ottica comunemente adottati per la celle solari in silicio cristallino possono condurre a risultati non accurati in caso di celle a film sottile e nanostrutturate. D'altra parte, i risolutori rigorosi delle equazioni di Maxwell sono altamente onerosi in termini computazionali. Recentemente, nella simulazione ottica di celle solari, il metodo RCWA ha acquisito una forte popolarità, fornendo un buon compromesso tra accuratezza e fabbisogno di risorse computazionali. Questa tesi rappresenta un contributo alla simulazione numerica -sia ottica che elettrica- di celle solari avanzate al silicio. Un simulatore numerico di dispositivi a semiconduttore 2-D/3-D allo stato dell'arte è stato applicato con successo alla simulazione di celle a doppia diffusione di emettitore a di celle con superficie posteriore passivata e contatto locale, per le quali è richiesta la multi-dimensionalità del modello di trasporto al fine di descrivere correttamente tutti i meccanismi fisici. Nella seconda parte della tesi, vengono discussi gli aspetti relativi alla simulazione ottica. Due innovative e computazionalmente efficienti implementazioni del metodo RCWA per domini di simulazione 2-D nonché un terzo simulatore RCWA per strutture 3-D basato sul calcolo di autovalori sono stati presentati in questa tesi. I simulatori proposti sono stati validati in termini di accuratezza, convergenza numerica, tempo di calcolo e correttezza dei risultati.

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49

Zanuccoli, Mauro <1974&gt. "Advanced Numerical Simulation of Silicon-Based Solar Cells." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4566/.

Full text

Abstract:

Photovoltaic (PV) conversion is the direct production of electrical energy from sun without involving the emission of polluting substances. In order to be competitive with other energy sources, cost of the PV technology must be reduced ensuring adequate conversion efficiencies. These goals have motivated the interest of researchers in investigating advanced designs of crystalline silicon solar (c-Si) cells. Since lowering the cost of PV devices involves the reduction of the volume of semiconductor, an effective light trapping strategy aimed at increasing the photon absorption is required. Modeling of solar cells by electro-optical numerical simulation is helpful to predict the performance of future generations devices exhibiting advanced light-trapping schemes and to provide new and more specific guidelines to industry. The approaches to optical simulation commonly adopted for c-Si solar cells may lead to inaccurate results in case of thin film and nano-stuctured solar cells. On the other hand, rigorous solvers of Maxwell equations are really cpu- and memory-intensive. Recently, in optical simulation of solar cells, the RCWA method has gained relevance, providing a good trade-off between accuracy and computational resources requirement. This thesis is a contribution to the numerical simulation of advanced silicon solar cells by means of a state-of-the-art numerical 2-D/3-D device simulator, that has been successfully applied to the simulation of selective emitter and the rear point contact solar cells, for which the multi-dimensionality of the transport model is required in order to properly account for all physical competing mechanisms. In the second part of the thesis, the optical problems is discussed. Two novel and computationally efficient RCWA implementations for 2-D simulation domains as well as a third RCWA for 3-D structures based on an eigenvalues calculation approach have been presented. The proposed simulators have been validated in terms of accuracy, numerical convergence, computation time and correctness of results. La conversione fotovoltaica è la produzione diretta di energia elettrica dal sole che non comporta l'emissione di sostanze inquinanti. Al fine di competere con altre fonti di energia, la tecnologia fotovoltaica deve subire una riduzione del costo garantendo contemporaneamente adeguate efficienze di conversione. Questi obiettivi hanno motivato l'interesse dei ricercatori al progetto ed all'analisi di celle solari avanzate in silicio cristallino. Poiché la riduzione del costo dei dispositivi fotovoltaici comporta tipicamente la riduzione del volume di semiconduttore, è necessaria una strategia efficace di intrappolamento della luce per aumentare l'assorbimento dei fotoni. Gli approcci orientati alla simulazione ottica comunemente adottati per la celle solari in silicio cristallino possono condurre a risultati non accurati in caso di celle a film sottile e nanostrutturate. D'altra parte, i risolutori rigorosi delle equazioni di Maxwell sono altamente onerosi in termini computazionali. Recentemente, nella simulazione ottica di celle solari, il metodo RCWA ha acquisito una forte popolarità, fornendo un buon compromesso tra accuratezza e fabbisogno di risorse computazionali. Questa tesi rappresenta un contributo alla simulazione numerica -sia ottica che elettrica- di celle solari avanzate al silicio. Un simulatore numerico di dispositivi a semiconduttore 2-D/3-D allo stato dell'arte è stato applicato con successo alla simulazione di celle a doppia diffusione di emettitore a di celle con superficie posteriore passivata e contatto locale, per le quali è richiesta la multi-dimensionalità del modello di trasporto al fine di descrivere correttamente tutti i meccanismi fisici. Nella seconda parte della tesi, vengono discussi gli aspetti relativi alla simulazione ottica. Due innovative e computazionalmente efficienti implementazioni del metodo RCWA per domini di simulazione 2-D nonché un terzo simulatore RCWA per strutture 3-D basato sul calcolo di autovalori sono stati presentati in questa tesi. I simulatori proposti sono stati validati in termini di accuratezza, convergenza numerica, tempo di calcolo e correttezza dei risultati.

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50

Levitsky, I. A. "Carbon Nanotubes - Si Hybrid Solar Cells." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35493.

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Abstract:

This short review describes recent results in the field of carbon nanotube (CNT) – Si hybrid photovolta-ics (PV) focusing on advantages of semiconducting carbon nanotubes over other organic materials used in organic- Si composite photosensing materials. Possible mechanisms of charge phogeneration at CNT- Si in-terface and chargte transport are discussed. Perspectives and future trends in research of this novel class of PV nanohybrids are presented as well. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35493

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