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1
Kerr, Mark John, and Mark Kerr@originenergy com au. "Surface, Emitter and Bulk Recombination in Silicon and Development of Silicon Nitride Passivated Solar Cells." The Australian National University. Faculty of Engineering and Information Technology, 2002. http://thesis.anu.edu.au./public/adt-ANU20040527.152717.
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¶
Recombination within the bulk and at the surfaces of crystalline silicon has been
investigated in this thesis. Special attention has been paid to the surface passivation achievable
with plasma enhanced chemical vapour deposited (PECVD) silicon nitride (SiN) films due to
their potential for widespread use in silicon solar cells. The passivation obtained with thermally
grown silicon oxide (SiO2) layers has also been extensively investigated for comparison.
¶
Injection-level dependent lifetime measurements have been used throughout this thesis to
quantify the different recombination rates in silicon. New techniques for interpreting the
effective lifetime in terms of device characteristics have been introduced, based on the physical
concept of a net photogeneration rate. The converse relationships for determining the effective
lifetime from measurements of the open-circuit voltage (Voc) under arbitrary illumination have
also been introduced, thus establishing the equivalency of the photoconductance and voltage
techniques, both quasi-static and transient, by allowing similar possibilities for all of them.
¶
The rate of intrinsic recombination in silicon is of fundamental importance. It has been
investigated as a function of injection level for both n-type and p-type silicon, for dopant
densities up to ~5x1016cm-3. Record high effective lifetimes, up to 32ms for high resistivity
silicon, have been measured. Importantly, the wafers where commercially sourced and had
undergone significant high temperature processing. A new, general parameterisation has been
proposed for the rate of band-to-band Auger recombination in crystalline silicon, which
accurately fits the experimental lifetime data for arbitrary injection level and arbitrary dopant
density. The limiting efficiency of crystalline silicon solar cells has been re-evaluated using this
new parameterisation, with the effects of photon recycling included.
¶
Surface recombination processes in silicon solar cells are becoming progressively more
important as industry drives towards thinner substrates and higher cell efficiencies. The surface
recombination properties of well-passivating SiN films on p-type and n-type silicon have been
comprehensively studied, with Seff values as low as 1cm/s being unambiguously determined.
The well-passivating SiN films optimised in this thesis are unique in that they are stoichiometric
in composition, rather than being silicon rich, a property which is attributed to the use of dilute
silane as a process gas. A simple physical model, based on recombination at the Si/SiN interface
being determined by a high fixed charge density within the SiN film (even under illumination),
has been proposed to explain the injection-level dependent Seff for a variety of differently doped
wafers. The passivation obtained with the optimised SiN films has been compared to that
obtained with high temperature thermal oxides (FGA and alnealed) and the limits imposed by
surface recombination on the efficiency of SiN passivated solar cells investigated. It is shown
that the optimised SiN films show little absorption of UV photons from the solar spectrum and
can be easily patterned by photolithography and wet chemical etching.
¶
The recombination properties of n+ and p+ emitters passivated with optimised SiN films
and thermal SiO2 have been extensively studied over a large range of emitter sheet resistances.
Both planar and random pyramid textured surfaces were studied for n+ emitters, where the
optimised SiN films were again found to be stoichiometric in composition. The optimised SiN
films provided good passivation of the heavily doped n+-Si/SiN interface, with the surface
recombination velocity increasing from 1400cm/s to 25000cm/s as the surface concentration of
electrically active phosphorus atoms increased from 7.5x1018cm-3 to 1.8x1020cm-3. The
optimised SiN films also provided reasonable passivation of industrial n+ emitters formed in a
belt-line furnace. It was found that the surface recombination properties of SiN passivated p+
emitters was poor and was worst for sheet resistances of ~150./ . The hypothesis that
recombination at the Si/SiN interface is determined by a high fixed charge density within the
SiN films was extended to explain this dependence on sheet resistance. The efficiency potential
of SiN passivated n+p cells has been investigated, with a sheet resistance of 80-100./ and a
base resistivity of 1-2.cm found to be optimal. Open-circuit voltages of 670-680mV and
efficiencies up to ~20% and ~23% appear possible for SiN passivated planar and textured cells
respectively. The recombination properties measured for emitters passivated with SiO2, both n+
and p+, were consistent with other studies and found to be superior to those obtained with SiN
passivation.
¶
Stoichiometric SiN films were used to passivate the front and rear surfaces of various
solar cell structures. Simplified PERC cells fabricated on 0.3.cm p-type silicon, with either a
planar or random pyramid textured front surface, produced high Vocs of 665-670mV and
conversion efficiencies up to 19.7%, which are amongst the highest obtained for SiN passivated
solar cells. Bifacial solar cells fabricated on planar, high resistivity n-type substrates (20.cm)
demonstrated Vocs up to 675mV, the highest ever reported for an all-SiN passivated cell, and
excellent bifaciality factors. Planar PERC cells fabricated on gettered 0.2.cm multicrystalline
silicon have also demonstrated very high Vocs of 655-659mV and conversion efficiencies up to
17.3% using a single layer anti-reflection coating. Short-wavelength internal quantum efficiency
measurements confirmed the excellent passivation achieved with the optimised stoichiometric
SiN films on n+ emitters, while long-wavelength measurements show that there is a loss of
short-circuit current at the rear surface of SiN passivated p-type cells. The latter loss is
attributed to parasitic shunting, which arises from an inversion layer at the rear surface due to
the high fixed charge (positive) density in the SiN layers. It has been demonstrated that that a
simple way to reduce the impact of the parasitic shunt is to etch away some of the silicon from
the rear contact dots. An alternative is to have locally diffused p+ regions under the rear
contacts, and a novel method to form a rear structure consisting of a local Al-BSF with SiN
passivation elsewhere, without using photolithography, has been demonstrated.
2
Chen, Wan Lam Florence Photovoltaics & 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.
3
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.
4
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.
5
Römer, Udo [Verfasser]. "Polycrystalline silicon/monocrystalline silicon junctions and their application as passivated contacts for Si solar cells / Udo Römer." Hannover : Technische Informationsbibliothek (TIB), 2016. http://d-nb.info/1096360942/34.
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Helland, Susanne. "Electrical Characterization of Amorphous Silicon Nitride Passivation Layers for Crystalline Silicon Solar Cells." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16310.
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High quality surface passivation is important for the reduction of recombination losses in solar cells. In this work, the passivation properties of amorphous hydrogenated silicon nitride for crystalline silicon solar cells were investigated, using electrical characterization, lifetime measurements and spectroscopic ellipsometry. Thin films of varying composition were deposited on p-type monocrystalline silicon wafers by plasma enhanced chemical vapor deposition (PECVD). Highest quality surface passivation was obtained for silicon-rich thin films, where a surface recombination velocity of 30 cm/s was obtained after a heat treatment corresponding to the industrial contact firing process. Electrical characterization of the interface between silicon nitride and silicon was performed by capacitance and conductance measurements. Several challenging aspects related to the interpretation of these measurements were investigated in detail, including charging and discharging, leakage currents, and frequency dependent capacitance.
7
Ramanathan, Saptharishi. "Understanding and development of dielectric passivated high efficiency silicon solar cells using spin-on solutions." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44771.
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In this work, spin-on processes were used to improve front- and rear-side technologies of solar cells to increase efficiencies to >20 %. A limited source diffusion process was developed using phosphoric acid dopant solutions developed in-house. An optimal emitter was obtained to be used in conjunction with screen-printed contacts. This emitter was used to improve the efficiency of conventional full aluminum back surface field solar cells to 19.6 %. A streamlined process was then developed to fabricate high-efficiency dielectric rear passivated cells in a single high temperature step. This process combined the diffusion process described earlier with a spin-on dielectric for rear passivation to achieve solar cell efficiencies of ~20%. Several laser candidates were investigated to improve process reproducibility and throughput. Ultra-violet laser with nanosecond pulse width was identified as the optimal choice. Cell efficiencies of ~20% were reproduced using UV laser for ablation of rear dielectric. This cell design and process were transferred to low-cost low-lifetime commercial grade substrates after identifying the optimal substrate characteristics using modeling.
8
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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Boge, Magnus. "Formation of silicon nanostructures in silicon nitride thin films for use in solar cells." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11058.
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The increase in the worlds demand for energy, and the fact that at one point we will run out of oil and gas which are two major contributers of the world supply of energy toady, are two reasons for why new and reliable energy sources are needed. The solar industry is one of the fastest growing industires, but the price of energy delivered by solar cells is still too high compared to other alternatives. More research is therefore needed in order to drive the price of solar energy down.In this report seven silicon nitride films with different stoichiometry are deposited on silicon substrate by the plasma enhanced chemical vapor de- position (PECVD) method. The deposition conditions are selected in order to enhance the formation of silicon nanoclusters. Silicon nanostructures have interesting properties due quantum effects observed at these dimensions. The most interesting of these properties is the ability to tune the silicon nanos- tructures to absrob ligth at different wavelengths. High energy light cannot be utilized in silicon solar cells. With the application of silicon nanostruc- tures, this light can be absorbed and down-converted to usable light which is then transmitted into the solar cell. This would increase the efficiency of the soalr cell, which results in cheaper energy. Two ensembles of as-deposited and annealed (annealed at 1050◦ C) samples were characterized with dif- ferent techniques in order to find the thickness, composition, light emitting sources and optical constants of the films. The techniques used were ellipsom- etry, photo-luminescence (PL) and transmission electron microscopy (TEM).The results obtained shows that all films are porous (indicated by the low index of refraction). One of the effects of annealing is an increase in the refractive index for all samples, which is an indication that the films have become more compact as a result of the annealing process. PL is obtained for samples with a high flow of ammonia, while samples of a low flow have little or no PL. The annealing process increase the PL observed for samples with a high ammonia flow, while a reduction is observed for the samples with a low flow. TEM images reveals that only one sample has any nanostructures present, so the observed PL is likely related to defect states.
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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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Sauaia, Rodrigo Lopes. "Development and analysis of silicon solar cells with laser-fired contacts and silicon nitride laser ablation." Pontifícia Universidade Católica do Rio Grande do Sul, 2013. http://hdl.handle.net/10923/5499.
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Previous issue date: 2013The goal of this thesis was the development and analysis of crystalline silicon solar cells processed by laser radiation. Solar cells with n+pp+ structure on p-type, CZ-Si solar grade substrate were developed, analysed, and evaluated, based on two laser processing techniques: laser-fired rear contacts (LFC) and laser ablation of the front surface silicon nitride by means of laser chemical processing (LPC) or using a mirror galvanometer laser system (SCA). The LFC method was employed to form the rear contacts of crystalline silicon solar cells after the deposition of an aluminium layer. The LCP and SOA methods were used to develop a silicon nitride ablation process. The laser ablation process was employed to open regions of the devices antireflection coating, followed by selective chemical deposition of Ni/Ag to form the front metal grid. The best laser processing parameters found for LFC solar cells were: 33. 0 A pumping lamp current, 20. 0 kHz q-switch frequency, and 0. 50 mm contact distance. LFC solar cells with screen printed front metallization and Si02 rear passivation layer achieved an average efficiency of 14. 4 % and best value of 15. 3 %, after an annealing step at 400 00 with a belt speed of 50 cm/min. lncreasing the rear aluminium layer thickness from 2 um to 4 um did not improve the performance of the devices significantly. The best laser processing parameters found for the silicon nitride laser ablation process based on the LCP technique were: 15. 3 uJ laser pulse energy, 16. 0 kHz q-switch frequency, and 100 mm/s processing speed. The best laser processing parameters found for the silicon nitride laser ablation process based on the SOA technique were: 5. 0 uJ laser pulse energy, 130. 0 kHz q-switch frequency, and 813 mm/s processing speed. Solar cells with silicon nitride laser ablation, front side metallization by Ni/Ag selective electrochemical deposition, and screen-printed rear side metallization achieved an average efficiency of 16. 1 % and best value of 16. 8 % for the LCP technique and an average efficiency of 16. 3 % and best value of 16. 6% for the SOA technique.
O objetivo desta tese foi o desenvolvimento e análise de células solares em substrato de silício cristalino com processamento por radiação laser. Células solares com estrutura n+pp+ em substrato de CZ-Si tipo p foram fabricadas, analisadas e comparadas, com base em duas técnicas de processamento laser: contatos posteriores formados por laser (CFL) e ablação do filme antirreflexo frontal de nitreto de silício por processamento químico com laser (PQL) ou por processamento com laser guiado por galvanômetro de espelhos (SCA). O método CFL foi utilizado na formação dos contatos posteriores de células solares, após a deposição de uma camada de alumínio. Os métodos PQL e SCA foram usados no desenvolvimento de um processo de ablação a laser do filme frontal de nitreto de silício. Trilhas foram abertas no filme antirreflexo e posteriormente metalizadas seletivamente por deposição química de níquel e prata, para formar a malha de metalização frontal. Os melhores parâmetros de processamento laser encontrados para células solares CFL foram: corrente da lâmpada de bombeamento óptico de 33,0 A, freqüência q-swttch de 20,0 kHz e distância entre contatos posteriores de 0,50 mm. Células solares CEL com metalização frontal por serigrafia e passivação posterior com SiO2 alcançaram uma eficiência média de 14,4 % e melhor valor de 15,3 %, após tratamento térmico a 400 °C com velocidade de esteira de 50 cm/min.O aumento da espessura da camada de alumínio posterior de 2 um para 4 um não resultou em melhora significativa da performance das células solares. Os melhores parâmetros de processamento encontrados para o processo de ablação a laser de nitreto de silício pela técnica PQL foram: energia do pulso laser de 15,3 uJ, frequência q-switch de 16,0 kHz e velocidade de processamento de 100 mm/s. Os melhores parâmetros de processamento encontrados para o processo de ablação a laser de nitreto de silicio pela técnica SCA foram: energia do pulso laser de 5,0 uJ, freqüência q-switch de 130,0 kHz e velocidade de processamento de 813 mm/s. Células solares com ablação a laser de nitreto de silicio, metalização frontal seletiva por deposição química de níquel e prata e metalização posterior por serigrafia atingiram a eficiência média de 16,1 % e o melhor valor de 16,8 % com a técnica PQL e a eficiência média de 16,3 % e melhor valor de 16,6 % com a técnica SCA.
12
Kranz, Christopher [Verfasser]. "Analysis and modeling of the rear side of industrial-type passivated emitter and rear silicon solar cells / Christopher Kranz." Hannover : Technische Informationsbibliothek (TIB), 2017. http://d-nb.info/1127248782/34.
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Urrejola, Elias [Verfasser]. "Aluminum-Silicon Contact Formation Through Narrow Dielectric Openings : Application To Industrial High Efficiency Rear Passivated Solar Cells / Elias Urrejola." Konstanz : Bibliothek der Universität Konstanz, 2012. http://d-nb.info/1023660032/34.
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Lai, Jiun-Hong. "Development of low-cost high-efficiency commercial-ready advanced silicon solar cells." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52234.
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The objective of the research in this thesis is to develop manufacturable high-efficiency silicon solar cells at low-cost through advanced cell design and technological innovations using industrially feasible processes and equipment on commercial grade Czochralski (Cz) large-area (239 cm2) silicon wafers. This is accomplished by reducing both the electrical and optical losses in solar cells through fundamental understanding, applied research and demonstrating the success by fabricating large-area commercial ready cells with much higher efficiency than the traditional Si cells. By developing and integrating multiple efficiency enhancement features, namely low-cost high sheet resistance homogeneous emitter, optimized surface passivation, optimized rear reflector, back line contacts, and improved screen-printing with narrow grid lines, 20.8% efficient screen-printed PERC (passivated emitter and rear cell) solar cells were achieved on commercial grade 239 cm2 p-type Cz silicon wafers.
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Yelundur, Vijay Nag. "Understanding and Implementation of Hydrogen Passivation of Defects in String Ribbon Silicon for High-Efficiency, Manufacturable, Silicon Solar Cells." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5271.
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Photovoltaics offers a unique solution to energy and environmental problems simultaneously. However, widespread application of photovoltaics will not be realized until costs are reduced by about a factor of four without sacrificing performance. Silicon crystallization and wafering account for about 55% of the photovoltaic module manufacturing cost, but can be reduced significantly if a ribbon silicon material, such as String Ribbon Si, is used as an alternative to cast Si. However, the growth of String Ribbon leads to a high density of electrically active bulk defects that limit the minority carrier lifetime and solar cell performance. The research tasks of this thesis focus on the understanding, development, and implementation of defect passivation techniques to increase the bulk carrier lifetime in String Ribbon Si in order to enhance solar cell efficiency. Hydrogen passivation of defects in Si can be performed during solar cell processing by utilizing the hydrogen available during plasma-enhanced chemical vapor deposition (PECVD) of SiNx:H films. It is shown in this thesis that hydrogen passivation of defects during the simultaneous anneal of a screen-printed Al layer on the back and a PECVD SiNx:H film increases the bulk lifetime in String Ribbon by more than 30 ?A three step physical model is proposed to explain the hydrogen defect passivation. Appropriate implementation of the Al-enhanced defect passivation treatment leads to String Ribbon solar cell efficiencies as high as 14.7%. Further enhancement of bulk lifetime up to 92 ?s achieved through in-situ NH3 plasma pretreatment and low-frequency (LF) plasma excitation during SiNx:H deposition followed by a rapid thermal anneal (RTA). Development of an optimized two-step RTA firing cycle for hydrogen passivation, the formation of an Al-doped back surface field, and screen-printed contact firing results in solar cell efficiencies as high as 15.6%. In the final task of this thesis, a rapid thermal treatment performed in a conveyer belt furnace is developed to achieve a peak efficiency of 15.9% with a bulk lifetime of 140 ?Simulations of further solar cell efficiency enhancement up to 17-18% are presented to provide guidance for future research.
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Morisset, Audrey. "Integration of poly-Si/SiOx contacts in silicon solar cells : Optimization and understanding of conduction and passivation properties." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS443.
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Dans le contexte des cellules photovoltaïques (PV) à base de silicium cristallin (c-Si), le développement de structures de contacts dits « passivants », qui permettent de limiter les pertes par recombinaisons des porteurs de charge à l’interface entre le métal et le c-Si, est un des principaux leviers vers l’obtention de plus hauts rendements. Une approche de contacts passivés consiste à intégrer entre le métal et le c-Si une jonction composée d’une couche de silicium poly-cristallin (poly-Si) fortement dopée sur une mince couche d’oxyde de silicium (SiOx < 2 nm).Les objectifs de ce travail sont d’une part de développer une jonction poly-Si/SiOx compatible avec la fabrication industrielle des cellules PV, et d’autre part d’améliorer la compréhension des mécanismes de passivation et de transport des charges au niveau de la fine couche de SiOx située à l’interface entre le poly-Si et le c-Si.Dans ce travail, une jonction de poly-Si/SiOx dopée au bore a été développée, le dopage de la couche étant dans un premier temps réalisé in-situ pendant l’étape de dépôt chimique en phase vapeur assisté par plasma (PECVD) de la couche poly-Si. La méthode de dépôt PECVD est répandue dans l’industrie PV et permet la fabrication de la couche poly-Si d’un seul côté du substrat c-Si. Cependant, elle induit une forte concentration d’hydrogène dans la couche déposée, ce qui entraine la formation de cloques à l’interface avec le c-Si et tend à dégrader les propriétés de passivation de surface de la jonction après recuit de cristallisation. L’optimisation des conditions de dépôt (température de dépôt et ratio de gaz H2/SiH4) a permis d’obtenir des couches de poly-Si dopées in-situ intègres. Par la suite, une méthode de dopage alternative, par le biais du dépôt d’une couche diélectrique riche en bore sur le poly-Si, a été appliquée afin de réduire l’apport en hydrogène pendant le dépôt et d’obtenir des couches de poly-Si intègres plus épaisses. L’ajout d’une étape d’hydrogénation a permis d’obtenir des propriétés de passivation de surface au niveau de l’état de l’art pour les deux types de jonctions poly-Si/SiOx développées.A la suite du développement de la jonction poly-Si/SiOx, la caractérisation physico-chimique de la couche SiOx a été réalisée et a démontré une possible amélioration de la stœchiométrie de la couche vers SiO2 ainsi qu’une dégradation de son homogénéité en épaisseur sous l’effet du recuit de cristallisation à haute température. Ces phénomènes pourraient s’expliquer par une diffusion des atomes d’oxygène à l’interface. D’autre part, l’étude du transport des charges à travers le SiOx par C-AFM a mis en évidence les limites de cette technique quant à la détermination de nano-ouvertures au sein de la couche SiOx (qui favoriseraient le transport des charges). Enfin, une méthode de caractérisation des défauts recombinants à l’interface entre une jonction de poly-Si intrinsèque et le c-Si a été mise en œuvre. Cette méthode a permis de modéliser les recombinaisons à l’interface poly-Si/c-Si via deux défauts discrets apparents dont les niveaux d’énergie dans la bande interdite et les ratios de sections efficaces de capture des électrons et des trous ont été déterminésIn the context of high efficiency solar cells (SCs) based on crystalline silicon (c-Si), the development of "passivating" contact structures to limit the recombination of charge carriers at the interface between the metal electrode and the c-Si has been identified as the next step to further improve the photovoltaic (PV) conversion efficiency. Passivating contacts consisting of a highly doped poly-crystalline silicon layer (poly-Si) on top of a thin layer of silicon oxide (SiOx ≤ 2 nm) are particularly sparking interest as they already demonstrated promising conversion efficiency when integrated in SCs.The objectives of this work are to develop a poly-Si/SiOx passivating contact compatible with the industrial production of c-Si SCs, and to investigate the passivation and charge transport mechanisms in the region of the thin SiOx layer located at the interface between the poly-Si and the c-Si.In this work, a boron-doped poly-Si/SiOx contact was fabricated. The doping of the layer was first performed in-situ during the deposition of a hydrogen-rich amorphous silicon (a-Si:H) layer by plasma-enhanced chemical vapor deposition (PECVD). The PECVD step was followed by an annealing step for crystallization of the poly-Si layer. The PECVD presents the advantages of being widespread in the PV industry and enabling the fabrication of the poly-Si contact on a single side of the c-Si substrate. However, it induces a high concentration of hydrogen in the deposited layer, which causes the formation of blisters at the interface with the c-Si and tends to degrade the surface passivation properties of the contact after annealing for crystallization. The optimization of the deposition conditions (temperature and H2/SiH4 gas ratio) enabled to obtain blister-free in-situ doped poly Si layers. An alternative doping method consisting of the deposition of a boron-rich dielectric layer on top of the poly-Si layer was applied to reduce the hydrogen content of the deposited layer. This approach enabled to obtain thicker blister-free poly-Si layers. The diffusion of hydrogen in the contact after annealing is known to provide a further chemical passivation of the poly-Si/c-Si interface. In this work, the addition of a hydrogenation step enabled to obtain state-of-the-art surface passivation properties for the two types of poly Si/SiOx contact fabricated.After developing the poly-Si/SiOx contact, a study of the effect of the annealing step on the chemical and structural properties of the SiOx layer was performed. Results indicated a possible improvement of the stoichiometry of the layer towards SiO2 as well as a degradation of its homogeneity at the poly-Si/c-Si interface after annealing at high temperature. These phenomena could be explained by a diffusion of the oxygen atoms content in the interfacial SiOx layer. The transport mechanism of charge carriers through the SiOx layer was conducted by C-AFM. This study revealed the limits of this technique to determine the presence of pinholes within the SiOx layer (that would help the transport of charge carriers). Finally, a method for characterizing recombinant defects at the interface between an intrinsic poly-Si junction and the c-Si has been developed. This method enabled to model the recombination phenomena at the poly-Si/c-Si interface via two apparent discrete defects. Their associated energy levels in the bandgap and ratios of electron and hole capture cross sections were estimated
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Anderson, Tom Harper. "Optoelectronic simulation of nonhomogeneous solar cells." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25892.
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This thesis investigates the possibility of enhancing the efficiency of thin film solar cells by including periodic material nonhomogeneities in combination with periodically corrugated back reflectors. Two different types of solar cell are investigated; p-i-n junctions solar cells made from alloys of hydrogenated amorphous silicon (a-Si:H) (containing either carbon or germanium), and Schottky barrier junction solar cells made from alloys of indium gallium nitride (InξGa1-ξN). Material nonhomogeneities are produced by varying the fractions of the constituent elements of the alloys. For example, by varying the content of carbon or germanium in the a-Si:H alloys, semiconductors with bandgaps ranging from 1:3 eV to 1:95 eV can be produced. Changing the bandgap alters both the optical and electrical properties of the material so this necessitates the use of coupled optical and electrical models. To date, the majority of solar cell simulations either prioritise the electrical portion of the simulation or they prioritise the optical portion of the simulation. In this thesis, a coupled optoelectronic model, developed using COMSOL Multiphysics®, was used to simulate solar cells: a two-dimensional finite-element optical model, which solved Maxwell's equations throughout the solar cells, was used to calculate the absorption of incident sunlight; and a finite-element electrical drift-diffusion transport model, either one- or two-dimensional depending on the symmetries of the problem, was used to calculate the steady state current densities throughout the solar cells under external voltage biases. It is shown that a periodically corrugated back reflector made from silver can increase efficiency of an a-Si:H alloy single p-i-n junction solar cell by 9:9% compared to a baseline design, while for a triple junction the improvement is a relatively meagre 1:8%. It is subsequently shown that the efficiency of these single p-i-n junction solar cells with a back reflector can be further increased by the inclusion of material nonhomogeneities, and that increasing the nonhomogeneity progressively increases efficiency, especially in thicker solar cells. In the case of InξGa1-ξN Schottky barrier junction solar cells, the gains are shown to be even greater. An overall increase in efficiency of up to 26:8% over a baseline design is reported.
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Sheoran, Manav. "Development of high-efficiency solar cells on thin silicon through design optimization and defect passivation." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/33902.
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The overall goal of this research is to improve fundamental understanding of the hydrogen passivation of defects in low-cost silicon and the fabrication of high-efficiency solar cells on thin crystalline silicon through low-cost technology development. A novel method was developed to estimate the flux of hydrogen, released from amorphous silicon nitride film, into the silicon. Rapid-firing-induced higher flux of hydrogen was found to be important for higher defect passivation. This was followed by the fabrication of solar cell efficiencies of ~ 17% on low-cost, planar cast multicrystalline silicon. Solar cell efficiencies and lifetime enhancement in the top, middle, and bottom regions of cast multicrystalline silicon ingots were explained on the basis of impurities and defects generally found in those regions. In an attempt to further reduce the cost, high-efficiency solar cells were fabricated on thin crystalline silicon wafers with full area aluminum-back surface field. In spite of loss in efficiency, wafer thinning reduced the module cost. Device modeling was performed to establish a roadmap towards high-efficiency thin cells and back surface recombination velocity and back surface reflectance were identified as critical parameters for high-efficiency thin cells. Screen-printed solar cells on float zone material, with efficiencies > 19% on 300 μm and > 18% on 140 μm were fabricated using a novel low-cost fabrication sequence that involved dielectric rear passivation along with local contacts and back surface field.
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Cheriton, Ross. "Design and Characterization of InGaN/GaN Dot-in-Nanowire Heterostructures for High Efficiency Solar Cells." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37905.
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Light from the sun is an attractive source of energy for its renewability, supply, scalability, and cost. Silicon solar cells are the dominant technology of choice for harnessing solar energy in the form of electricity, but the designs are approaching their practical efficiency limits. New multijunction designs which use the tunable properties of the more expensive III-V semiconductors have historically been relegated to space applications where absolute power conversion efficiency, resilience to radiation, and weight are more important considerations than cost. Some of the more recent developments in the field of semiconductor materials are the so-called III-nitride materials which mainly use either indium, aluminum or gallium in combination with nitrogen. Indium gallium nitride (InGaN) is one of these III-nitride semiconductor alloys that can be tailored to span the vast majority of the solar spectrum. While InGaN growth traditionally requires expensive substrate materials such as sapphire, three-dimensional nanowire growth modes enable high quality lattice mismatched growth of InGaN directly on silicon without a metamorphic buffer layer. The absorption and electronic properties of InGaN can also be tuned by incorporating it into quantum confined regions in a GaN host material. This opens up a route towards cost-effective, high efficiency devices such as light emitted diodes and solar cells which can operate over a large range of wavelengths. The combination of the two material systems of InGaN/GaN and silicon can marry the low cost of silicon wafers with the desirable optoelectronic properties of III-nitride semiconductors. This thesis investigates the potential for highly nanostructured InGaN/GaN based devices using quantum-dot-in-nanowire designs as novel solar cells which can enable intermediate band absorption effects and multiple junctions within a single nanowire to absorb more of the solar spectrum and operating more efficiently. Such semiconductor nanostructures can in principle reach power conversion efficiencies of over 40\% on silicon, with a cost closer to conventional silicon solar cells as opposed to methods which use non-silicon substrates.
In the primary strategy, the nanowires contain InGaN quantum dots which act as photon absorption/carrier generation centres to sequentially excite photons within the large band gap semiconductor. By using this intermediate band of states, large operating voltages between contacts can be maintained without sacrificing the collection of long wavelength solar photons. In this work, we characterize the properties of such nanowires and experimentally demonstrate sub-bandgap current generation in a large area InGaN/GaN dot-in-nanowire solar cell.
Experimental characterization of InGaN / GaN quantum dots in nanowires as both LEDs and solar cells is performed to determine the nanowire material parameters to understand how they relate to the nanowire device performance. Multiple microscopy techniques are performed to determine the nanowire morphology and contact effectiveness. Optical characterization of bare and fabricated nanowires is used to determine the anti-reflection properties of nanowire arrays. Photoluminescence and electroluminescence spectroscopy are performed. Illuminated current-voltage characteristics and quantum efficiencies are determined. Specular and diffuse reflectivities are measured as a function of wavelength.
Technology computer-aided design (TCAD) software is used to simulate the performance of the overall nanowire device. The contribution from quantum dots or quantum wells is simulated by solving for the carrier wavefunctions and density of states with the quantum structures. The discretized density of states from the quantum dots is modelled and used in a complete drift-diffusion device simulation to reproduce electroluminescence results. The carrier transport properties are modified to demonstrate effects on the overall device performance.
An alternate design is also proposed which uses an InGaN nanowire subcell on top of a silicon bottom subcell. The dual-junction design allows a broader absorption of the solar spectrum, increasing the operating voltage through monolithically grown series-connected, current-matched subcells. The performance of such a cell is simulated through drift-diffusion simulations of a dual-junction InGaN/Si solar cell. The effects of switching to a nanowire subcell based on the nanowires studied in this thesis is discussed.
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Sakano, Tomokazu Photovoltaics & Renewable Energy Engineering Faculty of Engineering UNSW. "Investigation of the SiN Deposition and effect of the hydrogenation on solid-phase crystallisation of evaporated thin-film silicon solar cells on glass." Publisher:University of New South Wales. Photovoltaics & Renewable Energy Engineering, 2008. http://handle.unsw.edu.au/1959.4/42134.
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One of the poly-Si thin-film cells developed at the University of New South Wales (UNSW) is the EVA cell. In this work, SiN films for EVA cells as an antireflection/barrier coating were investigated. In addition, the effect of hydrogenation pre-treatment of solid phase crystallisation (SPC) on grain size and open-circuit voltage (Voc) was investigated. The SiN films deposited by PECVD were examined for uniformity of the thickness and the refractive index of the films across the position of the samples in the PECVD deposition system. A spectrophotometric analysis was used to determine these film properties. It was found that these properties were very uniform over the deposition area. Good repeatability of the depositions was also observed. A series of SiN film depositions by reactive sputtering were also performed to optimize the deposition process. Parameters adjusted during the deposition were nitrogen flow rate, substrate bias, and substrate temperature. By investigating the deposition rate, refractive index, and surface roughness of the films, the three deposition parameters were optimised. The effects of post SiN deposition treatments (a-Si deposition, SPC, RTA, and hydrogenation) on thickness and refractive index of both SiN films deposited by PECVD and reactive sputtering were investigated by using samples which have the same structure as the EVA cells. The thickness of the PECVD SiN films decreased about 6 % after all the treatments. On the other hand, the thickness reductions of the reactively sputtered SiN films were very small. The refractive index of the PECVD SiN films increased about 0.6 % after the treatments, whereas that of the reactively sputtered SiN films decreased 1.3 % after the treatments. As a possible method to improve the performance of EVA cells, hydrogenation of a-Si was investigated as a pre-treatment of SPC process. There were no obvious differences in the grainsize and the Voc of the EVA cells with and without the hydrogenation. Therefore it is likely that the hydrogenation pre-treatment of SPC does not have a beneficial effect on the performance of EVA cells.
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Silva, Audrey Roberto 1964. "Texturização da superfície de silício monocristalino com NH4OH e camada antirrefletora para aplicações em células fotovoltaicas compatíveis com tecnologia CMOS = Texturing the surface of monocrystalline silicon with NH4OH and anti-reflective coating for applications in photovoltaic cells compatible with CMOS technology." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259291.
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Orientador: José Alexandre DinizDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-21T10:50:41Z (GMT). No. of bitstreams: 1 Silva_AudreyRoberto_M.pdf: 3023922 bytes, checksum: ee750f675d01f2b3ceebd5d74149b16e (MD5) Previous issue date: 2012
Resumo: Este trabalho apresenta o desenvolvimento de células fotovoltaicas de junção n+/p em substratos de Si com processos de fabricação totalmente compatíveis com a tecnologia CMOS (Complementary Metal Oxide Semiconductor). Os processos compatíveis desenvolvidos neste trabalho sao as técnicas: i) de texturização da superfície do Si, com reflexao da superficie texturizada de 15% obtida com a formação de micro-pirâmides (alturas entre 3 e 7 ?m), utilizando-se solução alcalina de NH4OH (hidróxido de amônia), que e livre da contaminação indesejável por íons de Na+ e K+ quando se utiliza soluções tradicionais de NaOH e de KOH, respectivamente, e ii) de deposição ECR-CVD (Electron Cyclotron Resonance - Chemical Vapor Deposition) da camada antirrefletora (ARC) de SiNX (nitreto de silício), que e executada em temperatura ambiente, portanto pode ser feita apos a finalização da célula sem danificar trilhas metálicas e alterar a profundidade da junção n+/p. A caracterização desta camada ARC mostrou que o nitreto tem índice de refração de 1,92 e refletância mínima de 1,03%, o que e um excelente resultado para uso em células solares (ou fotovoltaicas). Foram fabricadas cinco series de células fotovoltaicas, utilizando-se a texturização com NH4OH e a camada antirrefletora de nitreto de Si. Em quatro series utilizou-se o processo de implantação de íons de fósforo (31P+), com posterior recozimento, para a formação da região n+, enquanto que na quinta serie foi utilizado o processo de difusão térmica. As eficiências máximas para as células fabricadas são de 9% e de 12%, respectivamente, para as células feitas utilizando os processos de implantação e de difusão térmica, indicando que a implantação de íons causa danos na rede cristalina do silício, que o posterior recozimento não consegue corrigir, o que reduz a eficiência da célula
Abstract: This work presents the development of photovoltaic cells based on n+/p junction in Si substrates, with fully compatible fabrication processes with CMOS technology. The compatible processes, which are developed in this study, are the techniques: i) of Si surface texturing, with the textured surface reflection of 15% obtained by the formation of micro-pyramids (heights between 3 and 7 ?m) using NH4OH (ammonium hydroxide) alkaline solution, which is free of undesirable contamination by Na + and K + ions, when NaOH and KOH traditional solutions are used, respectively, and ii) of the ECR-CVD (Electron Cyclotron Resonance - Chemical Vapor Deposition) deposition of SiNx (silicon nitride) anti-reflective coating (ARC), which is carried out at room temperature and can be performed after the end of cell fabrication without damage on metallic tracks and without variation of n+/p junction depth. The ARC coating characterization presented that the silicon nitride has a refractive index of 1.92 and a minimum reflectance of 1.03%, which is an excellent result for application in solar (or photovoltaic) cells. Five series of photovoltaic cells were fabricated, using the NH4OH solution texturing and the silicon nitride antireflective coating. In the first four series, phosphorus (31P+) ion implantation process, with subsequent annealing to get the region n+, was used, while, in the fifth series was used the thermal diffusion process. The maximum efficiency values are of 9% and 12%, respectively, for cells, which were fabricated using the ion implantation and thermal diffusion processes, indicating that the ion implantation damages the silicon crystal lattice and the subsequent annealing cannot rectify, which reduces the cell efficiency
Mestrado
Eletrônica, Microeletrônica e Optoeletrônica
Mestre em Engenharia Elétrica
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Sobola, Dinara. "Nedestruktivní lokální diagnostika optoelektronických součástek." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-233678.
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Chceme-li využít nové materiály pro nová optoelektronická zařízení, potřebujeme hlouběji nahlédnout do jejich struktury. K tomu, abychom toho dosáhli, je však nutný vývoj a aplikace přesnějších diagnostických metod. Předložená disertační práce, jako můj příspěvek k částečnému dosažení tohoto cíle, se zabývá metodami lokální diagnostiky povrchu optoelektronických zařízení a jejich materiálů, většinou za využití nedestruktivních mechanických, elektrických a optických technik. Tyto techniky umožňují jednak pochopit podstatu a jednak zlepšit celkovou účinnost a spolehlivost optoelektronických struktur, které jsou obecně degradovány přítomností malých defektů, na nichž dochází k absorpci světla, vnitřnímu odrazu a dalším ztrátovým mechanismům. Hlavní úsilí disertační práce je zaměřeno na studium degradačních jevů, které jsou nejčastěji způsobeny celkovým i lokálním ohřevem, což vede ke zvýšené difúze iontů a vakancí v daných materiálech. Z množství optoelektronických zařízení, jsem zvolila dva reprezentaty: a) křemíkové solární články – součástky s velkým pn přechodem a b) tenké vrstvy – substráty pro mikro optoelektronická zařízení. V obou případech jsem provedla jejich detailní povrchovou charakterizaci. U solárních článků jsem použila sondovou mikroskopii jako hlavní nástroj pro nedestruktivní charakterizaci povrchových vlastností. Tyto metody jsou v práci popsány, a jejich pozitivní i negativní aspekty jsou vysvětleny na základě rešerše literatury a našich vlastních experimentů. Je také uvedeno stanovisko k použití sondy mikroskopických aplikací pro studium solárních článků. V případě tenkých vrstev jsem zvolila dva, z hlediska stability, zajímavé materiály, které jsou vhodnými kandidáty pro přípravu heterostruktury: safír a karbid křemíku. Ze získaných dat a analýzy obrazu jsem našla korelaci mezi povrchovými parametry a podmínkami růstu heterostruktur studovaných pro optoelektronické aplikace. Práce zdůvodňuje používání těchto perspektivních materiálů pro zlepšení účinnosti, stability a spolehlivosti optoelektronických zařízení.
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陳仲達. "Characteristic Simulation Analysis of Bifacial Silicon Nitride Passivated Screen-Printed Silicon Solar Cells." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/33947404845260067243.
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碩士國立清華大學
材料科學工程學系
101
The conventional solar cells have met their efficiency barrier at present and faced the mechanical problems when we use screen-printed process of back-side aluminum metallization. As the consequence, when we want to decrease cell thickness or use large-scale wafer for further reduction of fabrication cost of solar cells, this problem will be enlarged. Thus, we choose to use bifacial silicon nitride passivated screen-printed solar cells as the substitute structure which share almost the same fabrication process as the conventional one. Bifacial solar cells not only have none of the disadvantages mentioned above but can be applied to a variety of concentrated modules, so they show the promising potential to be the major products in the future. Due to many processing parameters in solar cell fabrication, we want to derive a complete analysis by simulation first. We use Sentaurus TCAD to simulate the performance of the cells and obtain the front limiting efficiency of 20.1% and back efficiency of 19.5% under the optimized metal coverage of 5.59%. In addition, the implementation of selective BSF can further improve front efficiency to 20.3% and back efficiency to 19.9%
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Kerr, Mark John. "Surface, Emitter and Bulk Recombination in Silicon and Development of Silicon Nitride Passivated Solar Cells." Phd thesis, 2002. http://hdl.handle.net/1885/47459.
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¶ Recombination within the bulk and at the surfaces of crystalline silicon has been investigated in this thesis. Special attention has been paid to the surface passivation achievable with plasma enhanced chemical vapour deposited (PECVD) silicon nitride (SiN) films due to their potential for widespread use in silicon solar cells. The passivation obtained with thermally grown silicon oxide (SiO2) layers has also been extensively investigated for comparison. ¶ Injection-level dependent lifetime measurements have been used throughout this thesis to quantify the different recombination rates in silicon. New techniques for interpreting the effective lifetime in terms of device characteristics have been introduced, based on the physical concept of a net photogeneration rate. The converse relationships for determining the effective lifetime from measurements of the open-circuit voltage (Voc) under arbitrary illumination have also been introduced, thus establishing the equivalency of the photoconductance and voltage techniques, both quasi-static and transient, by allowing similar possibilities for all of them. ¶ ...
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Huang, Chien-Lin, and 黃建霖. "Effects of Aluminum Oxide and Silicon Nitride Stacked Films on Photovoltaic Characteristics of Passivated Emitter and Rear Contact Silicon Solar Cells." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/7cd7jh.
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碩士國立虎尾科技大學
光電工程系光電與材料科技碩士班
105
In this study, the effects of aluminum oxide and silicon nitride stacked films on photovoltaic characteristics of passivated emitter and rear contact silicon solar cells were investigated. In general, the backside electrode of the screen-printed moncrystalline silicon solar cells was formed by screen-printed aluminum paste. However, the recombination rate of aluminum paste/p-type silicon interface is not good. Thus, the aluminum oxide (Al2O3) formed by atomic layer deposition (ALD) and metal organic chemical-vapor-deposition (MOCVD) as well as silicon nitride (SiNx) passivation layer formed by plasma enhanced chemical-vapor-deposition (PECVD) were investigated. By tuning the thickness and the composition of both Al2O3 and SiNx, the high quality stacked passivation layers were addressed. Moreover, the contact process of the Al2O3/SiNx stacked passivation layer were achieved by laser and wet chemical etching technique. The Nd:YAG laser with the wavelength of 1064 nm and the KOH solution for laser damage removal were presented for contact process. Regarding to the wet chemical etching technique, screen-printed polymer paste and the BOE etching solution were used for contact process. The results indicate that the Al2O3 thin film with interface trap charge of 2.061010 cm-2ev-1 deposited by ALD was better than that of MOCVD with interface trap charge of 1.741011 cm-2ev-1. The various thicknesses of silicon nitride ranged from 140 to 300 nm and aluminum oxide ranged from 10 to 30 nm were investigated. The results show that the better conversion efficiency (CE) was presented by combined the SiNx thickness of 180 nm with the Al2O3 thickness of 20 nm. Moreover, the composition effects of the SiNx were investigated by tuning SiH4/(SiH4+NH3) ratio. The results indicate that a good CE was achieved by the SiH4/(SiH4+NH3) at 0.45. Furthermore, the composition effects of the Al2O3 were investigated by tuning exposure time of trimethyl aluminum (TMA) and H2O. The results show that a good CE was demonstrated by the TMA with 0.04 s and H2O with 0.5 s exposure time. Finally, a good contact process was demonstrated by the laser with 1 W. According to the best parameters, a CE of 17.4 % with an open-circuit voltage (Voc) of 627 mV, and a short-circuit current density (Jsc) of 34.2 mA/cm2 were demonstrated in this work.
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McCann, Michelle Jane. "Aspects of Silicon Solar Cells: Thin-Film Cells and LPCVD Silicon Nitride." Phd thesis, 2002. http://hdl.handle.net/1885/47800.
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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.¶ ...
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Lin, Ting-Jui, and 林廷叡. "Silicon Solar Cells Passivated with Simple and Compound High-κ dielectric Materials." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/j8p7wh.
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碩士國立清華大學
電子工程研究所
101
In this thesis, we investigated simple and compound high-κ materials deposited by ALD as passivation layer for silicon solar cells. Silicon solar cells were fabricated with different passivation conditions such as without any high-κ passivation, with passivation only in the front end with Al2O3 (8Å), with passivation using Al2O3 (8Å) at the front end as well as at the rear end, with passivation using Al2O3 (8Å) at the front end and using Al2O3+HfO2 (8Å) at the rear end and with passivation using HfO2 (8Å) at the front end as well as at the rear end. Solar cell efficiency obtained for the cell without any high-κ passivation was 5.637% with a Jsc of 31.394mA/cm2, Voc of 0.43V and FF of 0.417. But with front end passivation using Al2O3 (8Å), cell efficiency improved to10.352% with a Jsc of 32.121mA/cm2, Voc of 0.51V and FF of 0.631. With passivation using Al2O3 (8Å) at the front end as well as at the rear end, Voc improved to 0.57V and efficiency was 14.353%. Jsc and FF obtained for this cell were 35.624mA/cm2 and 0.707, respectively. With passivation using Al2O3 (8Å) at the front end and using Al2O3+HfO2 (8Å) at the rear end, Voc improved to 0.58V and efficiency to 14.957% with a Jsc of 36.31 mA/cm2 and FF of 0.71. Finally with passivation using HfO2 (8Å) at the front end as well as at the rear end, efficiency of the cell increased to 15.542% while Voc improved to 0.59V.
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Wan, Yimao. "Highly transparent and highly passivating Silicon nitride for solar cells." Phd thesis, 2014. http://hdl.handle.net/1885/151507.
Full textAbstract:
This thesis concerns the optimisation and application of Silicon nitride (SiNx) films for silicon solar cells. Systematic and comprehensive studies of SiNx properties are undertaken to advance (i) the technology of SiNx synthesised by plasma enhanced chemical vapour deposition (PECVD), and (ii) the understanding of recombination at SiNx-passivated silicon surfaces. We examine the film properties of SiNx prepared by a microwave/radio-frequency dual-mode PECVD reactor. It is shown that there is no universal correlation between surface recombination and (i) bulk structural properties such as chemical bond densities, and (ii) bulk optical properties such as refractive index and extinction coefficient. Results of this study repudiate the common perception that surface recombination decreases as SiNx becomes Si-rich. The finding introduces the potential to independently control the optical and surface recombination properties of SiNx. This is of great importance for the industrial application of SiNx films to photovoltaic cells, as it allows the front surface transmission to be maximised while still attaining outstanding surface passivation. We attain a low and relatively constant surface recombination over a wide range of SiNx refractive indices. Notably, the behaviour is observed on several types of silicon surface surfaces-planar, textured, p-type, n-type, diffused and undiffused-with direct relevance to most silicon solar cell structures. The results confirm that the trade-off between the optical transmission and surface recombination is circumvented. In specific, we attain a highly transparent and highly passivating SiNx film. The value of this film is demonstrated on an n-type interdigitated back contact solar cell with no front surface diffusion, which makes the cell highly susceptible to the front surface passivation. On such a cell, the optimum SiNx developed in this thesis enables a conversion efficiency of 24.4 +/- 0.5% under standard testing conditions (25 Celsius degrees, AM1.5G spectrum). Besides the significant improvement in optical transmission and surface passivation, the results of this thesis also advance the current understanding of recombination at SiNx-passivated silicon surfaces. It is found that an increase in recombination of the textured surfaces is related to the presence of vertices and/or edges of the pyramids rather than to the presence of {111}-orientated facets. Furthermore, this thesis demonstrates that the increase in recombination introduced by (i) a lower pressure, leading to a higher refractive index, (ii) a higher NH3:SiH4 ratio, leading to a lower refractive index, and (iii) the vertices and/or edges of the pyramids, is primarily attributable to an increase in interface defect density rather than a decrease in SiNx charge density. In addition, we hypothesise that the increase in interface defect density is caused by an ion bombardment of the silicon surface at a lower pressure, and by an excessive incorporation of NHb radicals into the SiNx film network at a higher NH3:SiH4 ratio. The satisfactory resolution of the trade-off between optical transmission and surface passivation, and the improved understanding of recombination at SiNx-passivated silicon surfaces, represent significant contributions to the science and technology of silicon solar cells.
29
Jin, Hao. "Characterization of silicon / silicon dioxide / LPCVD silicon nitride stacks for solar cell application." Phd thesis, 2007. http://hdl.handle.net/1885/147115.
Full text
30
Allen, Thomas Gerald. "Addressing optical, recombination and resistive losses in crystalline silicon solar cells." Phd thesis, 2017. http://hdl.handle.net/1885/118238.
Full textAbstract:
The performance of any photovoltaic device is determined by its
ability to mitigate optical, recombination, and resistive energy
losses. This thesis investigates new materials and nascent
technologies to address these energy loss mechanisms in
crystalline silicon solar cells.
Optical losses, specifically the suppression of energy losses
resulting from front surface reflection, are first analysed. The
use of reactive ion etched black silicon texturing, a nano-scale
surface texture, is assessed with respect to the two conventional
texturing processes: isotexture and random pyramids. While
nano-scale surface textures offer a means of almost eliminating
front surface reflection, relatively poor internal optical
properties (i.e. light trapping) compared to both conventional
textures can compromise any optical gains realised on the front
surface. It is also shown that enhanced recombination losses
remains a barrier to the application of black silicon texturing
to further improve high performance devices, though this will
likely have less of an impact on multi-crystalline silicon cells
where bulk recombination dominates.
The suppression of recombination losses at surface defects by
gallium oxide (Ga2O3), an alternative to aluminium oxide (Al2O3),
is also investigated. It is demonstrated that, as in Al2O3, thin
films of amorphous Ga2O3 can passivate surface defects through a
direct reduction of recombination active defects and via the
establishment of a high negative charge density. Further
investigations demonstrate that Ga2O3 is applicable to random
pyramid surfaces textures, and is compatible with plasma enhanced
chemical vapour deposited silicon nitride (SiNx) capping for
anti-reflection purposes. Indeed, the Ga2O3 / SiNx stack is shown
to result in enhanced thermal stability and surface passivation
properties comparable to state-of-the-art Al2O3 films. In
addition, it is also shown that Ga2O3 can act as a Ga source in a
laser doping process, as demonstrated by a proof-of-concept
p-type laser doped partial rear contact solar cell with an
efficiency of 19.2%.
Finally, the resistive losses associated with metal / silicon
contacts are addressed. It is demonstrated that a significant
asymmetry in the work function of the electron and hole contact
materials is sufficient to induce carrier selectivity without the
need for heavy doping. This had recently been demonstrated for
hole contacts with the high work function material molybdenum
oxide. In this thesis specific attention is given to finding a
suitable low work function material for the electron contact.
Calcium, a common low work function electrode in organic
electronic devices, is shown to act as a low resistance Ohmic
contact to crystalline silicon without the need for heavy doping.
Fabrication of n-type solar cells with partial rear calcium
contacts resulted in a device efficiency of 20.3%, limited
largely by recombination at the Ca / Si interface. This
limitation to device efficiency is shown to be partially
alleviated by the application of a passivating titania (TiOx)
interlayer into the cell structure, resulting in an increase in
device efficiency to 21.8% -- the highest reported efficiency for
a TiOx-based heterojunction solar cell to date.
31
Fu, Po-Wei, and 傅柏瑋. "Improved Photovoltaic Characteristics of Passivated Emitter and Rear Contact Silicon Solar Cells by Electroplated Copper Technology." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/3ve9q5.
Full textAbstract:
碩士國立虎尾科技大學
光電工程系光電與材料科技碩士班
104
In this study, improved photovoltaic characteristics of passivated emitter and rear contact monocrystalline silicon solar cells (PERC) were demonstrated by electroplated copper technology. In general, high recombination velocity of screen-printed monocrystalline silicon solar cells (SPMSSCs) with aluminum paste as the back electrode was presented. Moreover, the series resistance of the SPMSSCs with aluminum paste was still high due to glass powder in aluminum paste. To improve these disadvantages, combined aluminum oxide (Al2O3) formed by metal-organic chemical-vapour-deposition (MOCVD) and silicon nitride (Si3N4) formed by plasma-enhanced chemical-vapour-deposition (PECVD) as passivation layer of PERC were investigated. Varoius laser grooves with various contact areas were formed by the Nd : YAG laser with a wavelength of 1064 nm. The laser parameters include various powers, the focus, the width, the laser dope, and the patterns. The laser damage and residue were removed by potassium hydroxide (KOH) solution. Simultaneously, the series resistance of the PERC was reduced by the nickel silicide/electroplating copper stacked films. Various parameters, including the thickness of the nickel seed layer, the electroplated time, the back passivation layer effects, were used to enhance the photovoltaic characteristics of the PERC. The results suggest that the conversion efficiencies of the PERC was demonstrated by the laser power of 7 %, the laser focus of 0 degree, the laser width of 5. The laser damage was removed by the potassium hydroxide solution with 1.1% for 1 min. The excellent nickel silicide was demonstrated by the nickel seed layer of thermal evaporated 500 nm and annealed at 400 ℃ for 7 min. A conversion efficiency of 15.8% with a open voltage (Voc) of 627 mV, a short current density (Jsc) of 31.4 mA/cm2, and a fill factor (F.F) of 0.745 were demonstrated by electroplated copper current density of 30 mA/cm2 for 40 minutes.
32
邱于凡. "Fabrication of Silicon Nitride Subwavelength Structures for Antireflection Coating of Solar Cells." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/97494862908522829499.
Full textAbstract:
碩士國立交通大學
材料科學與工程學系
98
Silicon nitride (SiNx) is a well-known single-layered antireflective and passive material for solar cells. Unfortunately, the single-layered antireflective coating (SLARC) generally works well within a limited spectral bandwidth. In this research, we develope a simple and low-cost method to fabricate subwavelength structure (SWS) on the SiNx to achieve a broadband antireflection with the objective of increasing the absorption of incident light for solar cells. First, a spin-coating process is carried out with adjustable spin rates, spin time, and concentrations of the dispersion containing SiO2 or PS particles. Subsequently, a single-layer microspherical array on the SiNx is formed. Next, the single-layer microspherical array is employed as the mask for following dry etching and wet etching. For dry etching, we use reactive ion etching (RIE) to etch SiNx and the reactive gas is a mixture of CF4 and O2. Depending on the mask material, a structure of pillar with parabolic surface is fabricated with the SiO2 nanosphere array; a cone structure is observed with the PS nanosphere array. The SiNx SWS with the height of 165 nm and the unetched SiNx thickness of 90 nm reveals excellent antireflective performance with the effective reflectance of 5.45% throughout the spectral range from 300 to 1000 nm. However, for wet etching, due to an unexpected poor adhesion between the substrate and mask, the desirable structure feature is not formed successfully.
33
"Modeling Towards Lattice-Matched Dilute Nitride GaNPAs on Silicon Multijunction Solar Cells." Doctoral diss., 2019. http://hdl.handle.net/2286/R.I.54918.
Full textAbstract:
abstract: Silicon photovoltaics is the dominant contribution to the global solar energy production. As increasing conversion efficiency has become one of the most important factors to lower the cost of photovoltaic systems, the idea of making a multijunction solar cell based on a silicon bottom cell has attracted broad interest. Here the potential of using dilute nitride GaNPAs alloys for a lattice-matched 3-terminal 2-junction Si-based tandem solar cell through multiscale modeling is investigated. To calculate the electronic band structure of dilute nitride alloys with relatively low computational cost, the sp^3 d^5 s^* s_N tight-binding model is chosen, as it has been demonstrated to obtain quantitatively correct trends for the lowest conduction band near Γ, L, and X for dilute-N GaNAs. A genetic algorithm is used to optimize the sp^3 d^5 s^* tight-binding model for pure GaP and GaAs for their optical properties. Then the optimized sp^3 d^5 s^* s_N parametrizations are obtained for GaNP and GaNAs by fitting to experimental bandgap values. After that, a virtual crystal approach gives the Hamiltonian for GaNPAs alloys. From their tight-binding Hamiltonian, the first-order optical response functions of dilute nitride GaNAs, GaNP, and GaNPAs are calculated. As the N mole fraction varies, the calculated critical optical features vary with the correct trends, and agree well with experiment. The calculated optical properties are then used as input for the solar device simulations based on Silvaco ATLAS. For device simulation, a bottom cell model is first constructed to generate performance results that agree well with a demonstrated high-efficiency Si heterojunction interdigitated back contact (IBC) solar cell reported by Kaneka. The front a-Si/c-Si interface is then replaced by a GaP/Si interface for the investigation of the sensitivity of the GaP/Si interface to interface defects in terms of degradation of the IBC cell performance, where we find that an electric field that induces strong band bending can significantly mitigate the impact of the interfacial traps. Finally, a lattice-matched 3-terminal 2-junction tandem model is built for performance simulation by stacking a dilute nitride GaNP(As) cell on the Si IBC cell connected through a GaP/Si interface. The two subcells operate quasi-independently. In this 3-terminal tandem model, traps at the GaP/Si interface still significantly impact the performance of the Si subcell, but their effects on the GaNP subcell are relatively small. Assuming the interfacial traps are well passivated, the tandem efficiency surpasses that of a single-junction Si cell, with values close to 33% based on realistic parameters.Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2019
34
Li, Kuan-Yu, and 李冠佑. "Development of Broadband Stacked Silicon Nitride Antireflection Coatings for Screen-Printed Monocrystalline Silicon Solar Cells Applications." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/84zj2c.
Full textAbstract:
碩士國立虎尾科技大學
光電工程系光電與材料科技碩士班
105
In this thesis, broadband stacked silicon nitride (SiNx) antireflection coatings were developed for screen-printed monocrystalline silicon solar cells (SPMSSCs) applications. The carrier generation rate can be enhanced by the reduction of the reflection. Moreover, the broadband antireflection can be presented by stacked antireflection coating. Furthermore, the open-circuit voltage can be improved by decreasing the surface recombination. Thus, the effects of the SiNx composition and stacked films formed by plasma enhanced chemical-vapor-deposition (PECVD) on photovoltaic characteristics of the SPMSSCs were investigated. The parameters of the composition effects, including flow rate of SiH4 and NH3, the thickness of the SiNx, and the SiNx stacked films ranged from two to four layers, were presented. The refraction, the thickness, the fixed oxide charge, and the interface trap charge in SiNx stacked films were evaluated by the n&k and the C-V measurement. The conversion efficiencies (CEs) of the SPMSSCs were also demonstrated. The results indicate that the interface trap density between SiNx/silicon interface decrease with increasing the flow rate of the SiH4. However, the refraction of SiNx increase with increasing the flow rate of the SiH4. Moreover, the positive fixed oxide charge increase with increasing the flow rate of the NH3. A better CE of the SPMSSCs was achieved by the SiH4/(SiH4+NH3) at 0.45 for one layer SiNx. A CE of 15.8% was demonstrated by the two layers stacked films with combined SiH4/(SiH4+NH3) at 0.63 for bottom layer and SiH4/(SiH4+NH3) at 0.09 for top layer. A CE of 16.7% was demonstrated by the three layers stacked films with combined SiH4/(SiH4+NH3) at 0.63 for bottom layer, SiH4/(SiH4+NH3) at 0.54 for intermediary layer and SiH4/(SiH4+NH3) at 0.09 for top layer. A CE of 16.4% was demonstrated by the four layers stacked films with combined SiH4/(SiH4+NH3) at 0.15 for bottom layer, SiH4/(SiH4+NH3) at 0.11 for second layer, SiH4/(SiH4+NH3) at 0.07 for third layer and SiH4/(SiH4+NH3) at 0.07 for top layer.
35
Sahoo, Kartika Chandra, and Kartika. "Design and Fabrication of Sub-wavelength Structures on Silicon Nitride for Solar Cells." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/63970518523390420268.
Full textAbstract:
博士國立交通大學
材料科學與工程系所
98
In this dissertation, we numerically study the reflectance of sub-wavelength structures on silicon nitride for solar cell application. Based on the numerical study, we develop a fabrication method to form the sub-wavelength structures on silicon nitride surface for solar cells. Since silicon nitride is a well known antireflection coating used in semiconductor industry, we explore the texturization on silicon nitride antireflection coating and its optical properties. The main motivation behind this lies in the fact that the sub-wavelength structures will act as a second antireflection coating layer with an effective refractive index so that the total structure can perform as a double layer antireflection coating layer. Thus, we could cost down the deposition of second antireflection coating layer can be saved with better or comparable performance as that of a double layer antireflection coating solar cell. In this study, we calculate the spectral reflectivity of pyramid-shaped silicon nitride sub-wavelength structures. A multilayer rigorous coupled-wave approach is advanced to investigate the reflection properties of silicon nitride sub-wavelength structure. We examine the simulation results for single layer antireflection and double layer antireflection coatings with sub-wavelength structure on silicon nitride surface, taking into account effective reflectivity over a range of wavelengths and solar efficiency. The results of our study show that a lowest effective reflectivity of 3.43% can be obtained for the examined silicon nitride sub-wavelength structure with the height of etched part of silicon nitride and the thickness of non-etched layer of 150 nm and 70 nm, respectively, which is less than the results of an optimized 80 nm silicon nitride single layer antireflection coating (~ 5.41%) and of an optimized double layer antireflection coating with 80 nm silicon nitride and 100 nm magnesium fluoride (~5.39%). 1% cell efficiency increase is observed for the optimized Si solar cell with silicon nitride sub-wavelength structure, compared with the cell with single layer silicon nitride antireflection coatings; furthermore, compared with double layer antireflection coated solar cell, the increase is about 0.71%. The improvement on the cell efficiency is mainly due to lower reflectance of silicon nitride sub-wavelength structure over a wavelength region from 400 nm to 600 nm that leads to lower short circuit current. Based upon our theoretical calculation of improved efficiency of silicon solar cell with silicon nitride sub-wavelength structures, we have developed a simple and scalable approach for fabricating sub-wavelength structures on silicon nitride by means of self-assembled nickel nano particle masks and inductively coupled plasma ion etching. The size and density of nickel nano particles are controlled by the initial thickness of nickel film that will be annealed to form the nano-particles on the silicon nitride film deposited on the silicon substrate. Inductively coupled plasma etching time is responsible for controlling the height of the fabricated silicon nitride sub-wavelength structure on silicon substrate. Nevertheless, the surface profile of a sub-wavelength structure is strongly dependent on the conditions of the reactive ion etching process. So, we have also investigated the effect of inductively coupled plasma etching conditions on the profile of fabricated sub-wavelength structure on Silicon nitride antireflection coating layers. At last, we succeeded in fabrication of nanopillar structures and nanocone structures on silicon nitride surface by one step and two step inductively coupled plasma etching methods. The relationship of etching time with structure height and average reflectance spectra has been drawn. In summary, design and fabrication of sub-wavelength structures on silicon nitride antireflective surface was investigated for the first time. The structure height and non-etched part of silicon nitride has been optimized for lowest effective reflectance by theoretical calculation using rigorous coupled wave analysis method. Also the shape effect has been studied theoretically. Based on theoretical results, the nanopillar and nanocone structures on silicon nitride surface have been fabricated successfully using self-assembled nickel nano clusters and inductively coupled plasma etching method. The achieved low reflectance is believed to be useful to improve the efficiency of solar cells. Also, the preliminary results for a silicon solar cell has been obtained using silicon nitride sub-wavelength structure, which shows a great promise in improvement of efficiency compared with a single layer antireflection coating.
36
劉廷軒. "Preparation of Silicon Nitride Protective Passivation Layer for High Efficiency PERC Solar Cells." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/durq56.
Full textAbstract:
碩士大葉大學
電機工程學系
105
In this study, silicon nitride films are deposited by inductively coupled plasma chemical vapor deposition with tetramethysilane (TMS) and ammonia (NH3) gas mixture. The deposition temperature (30-150 ℃), power (400-1600 W) and TMS gas flow rate (5-35) are varied to optimize the silcon nitride films. The experimental results show that at the TMS gas flow rate of 35 sccm, the film has high density and hydrogen content. At the power of 1200 W, the film has more Si-N bonds, and density. At the temperature of 120 ℃, the film is the most compact. The optimized deposition parameters are used to prepare different thickness of silicon nitride films. It is found that when the silcion nitride film thickenss is 120 nm covering on aluminum oxide and silicon wafer, the minority carrier lifetime is the highest, and the surface recombination velocity is the lowest. The lifetime is 1312.66 us and the surface recombination velocity is 18.06 cm/s. The secondary ion mass spectroscopy measurement result shows that the dense silicon nitride film can reduce hydrogen out-diffusion to environment, so the wafer lifetime will be increases due to the higher hydrogen content at silicon surface. The optimal experimental results are input in PC1D simulation, and the corresponded conversion efficiency of passivated emitter and rear contact solar cell is 20.91 % with an open-circuit voltage of 0.663 V, a short-circuit current density of 39.38 mA/cm2 and a FF of 80.05 %.
37
Lin, Hao-Yuan, and 林浩源. "Using Silicon Nitride Thin Film Combined with Silver Nanoparticles to Fabricate Low-reflective Silicon Nanostructure Solar Cells." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/69470150736770141912.
Full textAbstract:
碩士國立聯合大學
材料科學工程學系碩士班
103
Surface plasmon resonance (SPR) effect is suggested to be a popular topics recent studies to improve the performance of solar cells by nanoparticles, and anti-reflective layer on the solar cell applications have also been developed for a long time that it can enhance the efficiency of the solar cell by lower surface reflection and passivation. In this study, we combined these two processes. For nanoparticle fabrication, we sputtered a layer of silver film on the silicon nanopillar solar cell, and then used the inductively coupled plasma (ICP) by controlling the RF power and etching duration to fabricate silver nanoparticles with different sizes. For antireflective coating, we performed the optimization on thickness for the deposition of nitride layer on silicon nanopillar solar cells before and after ICP plasma etching to investigate the effects of both SPR and nitride coating on the performance of nanopillar solar cells. The results show that the nanopillar solar cells with 75 nm antireflection layer have the lowest reflectance (2.3 %) and the highest efficiency (12.65 %). In the following three different structures (nanoparticles on nitride coating, nitride coating on nanoparticle, and sandwich structure) we found that the performance of solar cells can be improved by plasma etching sliver thin film on a 75 nm antireflection layer, in which the surface reflection was reduced from 9.8 % to 1.8 % and the efficiency was increased from 8.05 % to 9.50 %. We believe that the antireflective layer and SPR contribute to these results.
38
Li, Chuan. "Surface and bulk passivation of multicrystalline silicon solar cells by silicon nitride (H) layer modeling and experiments /." Thesis, 2009. http://library1.njit.edu/etd/fromwebvoyage.cfm?id=njit-etd2009-009.
Full textAbstract:
Thesis (Ph.D) -- New Jersey Institute of Technology, Committee for the Interdisciplinary Program in Materials Science and Engineering, 2009.Includes bibliographical references. Also available via the World Wide Web.
39
"Study of Charges Present in Silicon Nitride Thin Films and Their Effect on Silicon Solar Cell Efficiencies." Doctoral diss., 2013. http://hdl.handle.net/2286/R.I.18821.
Full textAbstract:
abstract: As crystalline silicon solar cells continue to get thinner, the recombination of carriers at the surfaces of the cell plays an ever-important role in controlling the cell efficiency. One tool to minimize surface recombination is field effect passivation from the charges present in the thin films applied on the cell surfaces. The focus of this work is to understand the properties of charges present in the SiNx films and then to develop a mechanism to manipulate the polarity of charges to either negative or positive based on the end-application. Specific silicon-nitrogen dangling bonds (·Si-N), known as K center defects, are the primary charge trapping defects present in the SiNx films. A custom built corona charging tool was used to externally inject positive or negative charges in the SiNx film. Detailed Capacitance-Voltage (C-V) measurements taken on corona charged SiNx samples confirmed the presence of a net positive or negative charge density, as high as +/- 8 x 1012 cm-2, present in the SiNx film. High-energy (~ 4.9 eV) UV radiation was used to control and neutralize the charges in the SiNx films. Electron-Spin-Resonance (ESR) technique was used to detect and quantify the density of neutral K0 defects that are paramagnetically active. The density of the neutral K0 defects increased after UV treatment and decreased after high temperature annealing and charging treatments. Etch-back C-V measurements on SiNx films showed that the K centers are spread throughout the bulk of the SiNx film and not just near the SiNx-Si interface. It was also shown that the negative injected charges in the SiNx film were stable and present even after 1 year under indoor room-temperature conditions. Lastly, a stack of SiO2/SiNx dielectric layers applicable to standard commercial solar cells was developed using a low temperature (< 400 °C) PECVD process. Excellent surface passivation on FZ and CZ Si substrates for both n- and p-type samples was achieved by manipulating and controlling the charge in SiNx films.Dissertation/Thesis
Ph.D. Electrical Engineering 2013
40
"Charged Silicon Nitride Films: Field-Effect Passivation of Silicon Solar Cells and a Novel Characterization Method through Lifetime Measurements." Master's thesis, 2014. http://hdl.handle.net/2286/R.I.24975.
Full textAbstract:
abstract: Silicon (Si) solar cells are the dominant technology used in the Photovoltaics industry. Field-effect passivation by means of electrostatic charges stored in an overlying insulator on a silicon solar cell has been proven to be a significantly efficient way to reduce effective surface recombination velocity and increase minority carrier lifetime. Silicon nitride (SiNx) films have been extensively used as passivation layers. The capability to store charges makes SiNx a promising material for excellent feild effect passivation. In this work, symmetrical Si/SiO2/SiNx stacks are developed to study the effect of charges in SiNx films. SiO2 films work as barrier layers. Corona charging technique showed the ability to inject charges into the SiNx films in a short time. Minority carrier lifetimes of the Czochralski (CZ) Si wafers increased significantly after either positive or negative charging. A fast and contactless method to characterize the charged overlying insulators on Si wafer through lifetime measurements is proposed and studied in this work, to overcome the drawbacks of capacitance-voltage (CV) measurements such as time consuming, induction of contanmination and hysteresis effect, etc. Analytical simulations showed behaviors of inverse lifetime (Auger corrected) vs. minority carrier density curves depend on insulator charge densities (Nf). From the curve behavior, the Si surface condition and region of Nf can be estimated. When the silicon surface is at high strong inversion or high accumulation, insulator charge density (Nf) or surface recombination velocity parameters (Sn0 and Sp0) can be determined from the slope of inverse lifetime curves, if the other variable is known. If Sn0 and Sp0 are unknown, Nf values of different samples can be compared as long as all have similar Sn0 and Sp0 values. Using the saturation current density (J0) and intercept fit extracted from the lifetime measurement, the bulk lifetime can be calculated. Therefore, this method is feasible and promising for charged insulator characterization.Dissertation/Thesis
M.S. Electrical Engineering 2014
41
YOU, CHENG-YUN, and 游承澐. "Effects of Chemical Etching and Silicon Nitride Passivation on the Performance of Superstructured Micropillar Solar Cells." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/v8842e.
Full textAbstract:
碩士國立聯合大學
材料科學工程學系碩士班
104
We combined silicon micropillar array structure with black silicon to create a dual-scale superstructure, and applied PECVD silicon nitride as a passivation to improve the electrical properties of this superstructure solar cell. Silicon micropillars with 1-m diameter were fabricated by I-line lithography, and metal assisted chemical etching was used to produce black silicon atop micropillars. We controlled silver ion concentration and etching time to investigate the morphology evolution and the corresponding optical and electrical properties, and found that power conversion efficiency (PCE) reached a maximum under an appropriate etching time. As the silver ion concentration decreased, the optimal etching time was expanded, suggesting that less surface area increased with decreasing ion concentration. Furthermore, we found that the weighted reflection over broad band of micropillar can be reduced substantially by a thin black-silicon layer. When the superstructure was passivated by a conventional PECVD nitride, the PCE was further improved apparently because the black-silicon was thin. For example, as the PCEs of black silicon and micropillar were 9.35% and 9.61%, respectively, the PCEs for superstructure without and with passivation were improved to be 10.06% and 11.05%, respectively. These results show that the dual-scale provides a paradigm to concurrently improve the optical and electrical properties because of the lower reflection and well-passivated surface of nanostructures.
42
Ren, Yongling. "Trapping and decay of negative charge in silicon nitride films for photovoltaic applications." Phd thesis, 2011. http://hdl.handle.net/1885/150795.
Full textAbstract:
Surface passivation is a major technology area requiring improvement in order to increase device efficiency for most commercial solar cells. As the thickness of solar cells continues to decrease, surface passivation becomes even more important as the efficiency loss due to poorly passivated surfaces becomes greater. This thesis aims to combine the excellent passivation properties of silicon nitride (SiN
43
LI, JIA-ZHAN, and 李佳展. "Effects of Screen-Printed and Atomic-Layer-Deposition Aluminum Oxide Stacked Films on Photovoltaic Characteristics of Passivated Emitter and Rear Contact Silicon Solar Cells." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/2dxnr9.
Full textAbstract:
碩士國立虎尾科技大學
光電工程系光電與材料科技碩士班
106
In this study, the effects of screen-printed and atomic-layer-deposition (ALD) aluminum oxide (Al2O3) stacked films on photovoltaic characteristics of passivated emitter and rear contact (PERC) silicon solar cells were investigated. In general, the backside electrode of the screen-printed monocrystalline silicon solar cells was formed by aluminum back-surface-field (Al-BSF) with recombination rate of 200 to 600 cm/s. Currently, to reduce the high recombination rate of the Al-BSF and increase the field-effect passivation with negative charge, Al2O3 and silicon nitride (Si3N4) stacked films are mostly used on the back surface in commercial PERC cells. Moreover, the laser drilling process in PERC cells is complication. Therefore, in this work, screen-printed Al2O3 paste and ALD Al2O3 layer were adopted as the passivation layer and barrier layer, respectively. The parameters of the screen-printed Al2O3 paste, including the colloidal type of Al2O3 paste, the thickness of the emulsion, the gap of the screen, and the contact fraction between Al paste and silicon substrate, were presented. Next, the various thicknesses of the ALD Al2O3 passivation layers and effects of after ALD Al2O3 were investigated. At the same time, the effects of the Al2O3 stacked films formed by screen-printed and ALD techniques on the passivation layers of the PERC cells were addressed. The results indicated that the enhanced properties of the diffusion barrier can be demonstrated by increasing the viscosity in the Al2O3 paste when changing the colloidal types of the Al2O3 paste. When changing the thickness of the Al2O3 paste from 5 to 20 μm, it was found that the minimum thickness of the Al2O3 paste with around 10 μm was demonstrated for the thickness of the emulsion at 5 μm. When changing the gap of the screen ranged from 1.1 to 1.3, a thinner diffusion barrier layer can be achieved by a gap of 1.1. In the case of changing the different contact fraction, it was found that the better photovoltaic characteristics were presented by the contact fraction of 30 % combined with the gap of Al paste at 1.4 and the gap of the Ag paste at 1.6, a CE of 17.77 %. The photovoltaic characteristics of the PERC cells with screen-printed Al2O3 paste only can be enhanced by the combination of screen-printed and ALD deposited Al2O3 passivation layers. When changing the thickness of by ALD Al2O3 from 0 to 9 nm, it was found the thickness the best by ALD Al2O3 of 6 nm. When changing the after ALD Al2O3 of processing etched time from 0 to 15 sec, it was found the etched time the best of 5 sec. According to the optimum parameters, a CE of 18.0 % with an open-circuit voltage (Voc) of 641 mV, a short-circuit current density (Jsc) of 35.7 mA/cm2, a series resistance (Rs) of 1.6 Ω-cm2, and a fill factor (F.F.) of 80.01 % were demonstrated.
44
Kuo, Ting-Wei, and 郭庭維. "Effects of antireflection-coating silicon nitride films deposited by pulse-modulated plasma-enhanced chemical vapor deposition on potential-induced degradation of silicon solar cells." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/00163403351974654088.
Full textAbstract:
碩士國立交通大學
光電科技學程
104
A phenomenon called potential-induced degradation (PID) has been found out in solar cell module by SunPower Co. in 2005, which can cause the power conversion efficiency of solar cells drop sharply. Since that, solar cell industries and academic researchers have put a lot of effort to investigate PID and find out solutions for it. There are different ways to solve PID depending on the levels of modules and system. In consideration of cost, conversion efficiency, throughput and other issues, the typical solution is to increase the refractive index of a-SiNx:H thin film of solar cell. However, the conversion efficiency decreases as well. In general, a-SiNx:H thin film of solar cell is deposited by plasma enhanced chemical vapor deposition (PECVD). In this experiment, we investigated the properties of a-SiNx:H thin films deposited by conventional continuous mode and pulse-modulated mode of PECVD and compared their performances of PID resistance. To understand how the properties of a-SiNx:H film influence on PID effect and conversion efficiency, a-SiNx:H films of solar cells with refractive index of 2.07, 2.11, and 2.16 are deposited by continuous and pulse-modulated mode, respectively. Then those solar cells were performed PID test for 48 and 96 hours and the optical properties, electrical properties, etching rate, and composition of these a-SiNx:H films were investigated. Considering whether thickness of a-SiNx:H film influence on performance of anti-PID, solar cells with different thickness of a-SiNx:H films deposited by continuous mode are performed PID test. Finally, we discussed why the performance of PID resistance of a-SiNx:H film deposited by continuous mode is better than that deposited by pulse-modulated mode. For the future work, the PID resistance of a-SiNx:H films deposited by pulse-modulated mode can be improved by increasing the composition of Si by decreasing the duty cycle of pulse-modulated plasma.