Dissertations / Theses on the topic 'Low-Cost silicon'
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Duran, Joshua. "Silicon-Based Infrared Photodetectors for Low-Cost Imaging Applications." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton155653478017603.
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Orholor, Ayomanor Benedict. "The production of low-cost solar grade silicon from rice husk." Thesis, Sheffield Hallam University, 2017. http://shura.shu.ac.uk/23502/.
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Rice husk, an agricultural waste product obtained in large quantities in many countries including Nigeria, is very rich in siliceous materials. It has been known for several decades that, with careful processing, rice husk can be a source of metallurgical grade silicon. In Nigeria this would have the benefit of transforming large volumes (> 600,000 tonnes per annum) of agricultural waste into a partial solution to that country's issue with energy distribution. In this work, silica of between 95.24% and 98.03% purity has been prepared from RHA (ashed at 700°C, 800°C, 900°C and 1000°C for either 5hrs or 12 hours). Additionally, the silica value was boosted by use of hydrometallurgical purification process. The improved purification processes yielded 99.18% and 99.51% of silica. Removal of many metallic trace impurities was significant: MgO (98.33%), AI2O3 (96.77%), Mn3O4 (80%), SO3 (55%), CaO (97.92%), B (73.91%) and P2O5 (88.34%) are removed by leaching. Impurities such as Na2O, Fe2O3 and K2O are almost completely leached out beyond detection of the XRF after the final processing step. Metallothermic reduction of the purified RHA with magnesium was investigated and post hydrometallurgical purification to further eliminate all soluble impurity. XRF and EDS showed P was reduced below their detection limit. The XRD showed that RHA transformation from amorphous to crystalline material depends on temperature and time. TEM investigation shows that derived silicon consist of agglomerate polycrystalline materials. TG analysed the the devolatilization, combustion and mass gain in RHA. The effectiveness of each stage of hydrometallurgical process in removing impurity elements was presented. While the hydrometallurgical purification of RHA is effective in removing impurities such as Ti and Fe to levels below the limits of detection of X-ray fluorescence (XRF), B levels was reduced to 22 ppm. Solvent refining process was done using Sn as a selected gettering metal for B in silicon.
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Prabhakar, Sandesh. "Algorithms and Low Cost Architectures for Trace Buffer-Based Silicon Debug." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/35931.
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An effective silicon debug technique uses a trace buffer to monitor and capture a portion of the circuit response during its functional, post-silicon operation. Due to the limited space of the available trace buffer, selection of the critical trace signals plays an important role in both minimizing the number of signals traced and maximizing the observability/restorability of other untraced signals during post-silicon validation. In this thesis, a new method is proposed for trace buffer signal selection for the purpose of post-silicon debug. The selection is performed by favoring those signals with the most number of implications that are not implied by other signals. Then, based on the values of the traced signals during silicon debug, an algorithm which uses a SAT-based multi-node implication engine is introduced to restore the values of untraced signals across multiple time-frames. A new multiplexer-based trace signal interconnection scheme and a new heuristic for trace signal selection based on implication-based correlation are also described. By this approach, we can effectively trace twice as many signals with the same trace buffer width. A SAT-based greedy heuristic is also proposed to prune the selected trace signal list further to take into account those multi-node implications. A state restoration algorithm is developed for the multiplexer-based trace signal interconnection scheme. Experimental results show that the proposed approaches select the trace signals effectively, giving a high restoration percentage compared with other techniques. We finally propose a lossless compression technique to increase the capacity of the trace buffer. We propose real-time compression of the trace data using Frequency-Directed Run-Length (FDR) code. In addition, we also propose source transformation functions, namely difference vector computation, efficient ordering of trace flip-flops and alternate vector reversal that reduces the entropy of the trace data, making them more amenable for compression. The order of the trace flip-flops is computed off-chip using a probabilistic algorithm. The difference vector computation and alternate vector reversal are implemented on-chip and incurs negligible hardware overhead. Experimental results for sequential benchmark circuits shows that this method gives a better compression percentage compared to dictionary-based techniques and yields up to 3X improvement in the diagnostic capability. We also observe that the area overhead of the proposed approach is less compared to dictionary-based compression techniques.Master of Science
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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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Krygowski, Thomas Wendell. "A novel simultaneous diffusion technology for low-cost, high-efficiency silicon solar cells." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/22973.
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Chen, Chia-Wei. "Low cost high efficiency screen printed solar cells on Cz and epitaxial silicon." Diss., Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/54968.
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The objective of this research is to achieve high-efficiency, low-cost, commercial-ready, screen-printed Silicon (Si) solar cells by reducing material costs and raising cell efficiencies. Two specific solutions to material cost reduction are implemented in this thesis. The first one is low to medium concentrator (2-20 suns) Si solar cells. By using some optics to concentrate sunlight, the same amount of output power can be achieved with cell area reduced by a factor equal to the concentration ratio. Since the cost of optics is less than the semiconductor material, electricity price from the concentrator photovoltaics (PV) system is therefore reduced. The second solution is the use of epitaxially grown Si (epi-Si) wafers. This epi-Si technology bypasses three costly process steps (the need for polycrystalline silicon feedstock, ingot growth, and wafer slicing) compared to the traditional Si wafer technology and therefore reduces the material cost by up to 50% in a finished PV module. In addition, high efficiency Si solar cells with reduced metal contact recombination are studied and modeled by implementation of passivated contacts composed of tunnel oxide, n+ polycrystalline Si and metal on top of n-type Si absorber to reduce the cost ($/Wp) of PV module.
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Ryu, Kyung Sun. "Development of low-cost and high-efficiency commercial size n-type silicon solar cells." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53842.
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The objective of the research in this thesis was to develop high-efficiency n-type silicon solar cells at low-cost to reach grid parity. This was accomplished by reducing the electrical and optical losses in solar cells through understanding of fundamental physics and loss mechanisms, development of process technologies, cell design, and modeling. All these technology enhancements provided a 3.44% absolute increase in efficiency over the 17.4% efficient n-type PERT solar cell. Finally, 20.84% efficient n-type PERT (passivated emitter and rear totally diffused) solar cells were achieved on commercial grade 239cm2 n-type Cz silicon wafers with optimized front boron emitter without boron-rich layer and phosphorus back surface field, silicon dioxide/silicon nitride stack for surface passivation, optimized front grid pattern with screen printed 5 busbars and 100 gridlines, and improved rear contact with laser opening and physical vapor deposition aluminum. This thesis also suggested research directions to improve cell efficiency further and attain ≥21% efficient n-type solar cells which involves three additional technology developments including the use of floating busbars, selective emitters, and negatively charged aluminum oxide (Al2O3) film for boron emitter surface passivation.
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Berrada, Sounni Amine. "Low cost manufacturing of light trapping features on multi-crystalline silicon solar cells : jet etching method and cost analysis." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61522.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 127-128).
An experimental study was conducted in order to determine low cost methods to improve the light trapping ability of multi-crystalline solar cells. We focused our work on improving current wet etching methods to achieve the desired light trapping features which consists in micro-scale trenches with parabolic cross-sectional profiles with a target aspect ratio of 1.0. The jet etching with a hard mask method, which consists in impinging a liquid mixture of hydrofluoric, nitric and acetic acids through the opening of hard mask, was developed. First, a computational fluid dynamics simulation was conducted to determine the desired jet velocity and angle to be used in our experiments. We find that using a jet velocity of 3 m/s and a jetting angle of 45° yields the necessary flow characteristics for etching high aspect ratio features. Second, we performed experiments to determine the effect of jet etching using a photo-resist mask and thermally grown silicon oxide mask on multiple silicon substrates : <100>, <110>, <111> and multi-crystalline silicon. Compared to a baseline of etching with no jet, we find that the jet etching process can improve the light trapping ability of the baseline features by improving their aspect ratio up to 65.2% and their light trapping ability up to 38.1%. The highest aspect ratio achieved using the jet etching process was 0.62. However, it must be noted that the repeatability of the results was not consistent: significant variations in the results of the same experiment occurred, making the jet etching process promising but difficult to control. Finally, we performed a cost analysis in order to determine the minimum efficiency that a jet etching process would have to achieve to be cost competitive and its corresponding features aspect ratio. We find that a minimum cell efficiency of 16.63% and feature aspect ratios of 0.57 are necessary for cost competitiveness with current solar cell manufacturing technology.
by Amine Berrada Sounni.
S.M.in Technology and Policy
S.M.
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Statnikov, Konstantin [Verfasser]. "Towards Multi-Dimensional Terahertz Imaging Systems Based on Low-Cost Silicon Technologies / Konstantin Statnikov." München : Verlag Dr. Hut, 2016. http://d-nb.info/1097818268/34.
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Lopez, Parra Marcelo. "The design, manufacture and testing of a low-cost cleanroom robot for handling silicon wafers." Thesis, Cranfield University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260098.
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Chen, Qiao. "Modeling, design and demonstration of through-package-vias in panel-based polycrystalline silicon interposers for high performance, high reliability and low cost." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53568.
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Silicon interposers with TSVs (through-silicon-vias) have been developed in single-crystalline silicon wafer to achieve the high I/O (Input/Output) density. However, single-crystalline silicon interposers suffer a few problems such as cost, electrical performance and reliability. To overcome these shortcomings, an entirely different approach using polycrystalline silicon interposers with thick polymer liners are proposed by Georgia Tech Packaging Research Center, aiming to achieve lower cost silicon interposers with high performance and reliability.
The objective of this research is to explore and demonstrate thin polycrystalline silicon as a suitable interposer material to achieve high performance and high reliability TPVs (through-package-vias) in polycrystalline silicon materials with lower cost. Three fundamental challenges were defined, including: 1) low resistivity of the polycrystalline silicon, resulting in high electrical loss; 2) reliability problems resulting from CTE (coefficient of thermal expansion) mismatch between silicon and Cu, and 3) handling and processing of thin silicon panels.
A three-dimensional EM (electromagnetic) model was developed to simulate insertion loss and crosstalk of TPVs and compared with TSVs. It has been shown thick polymer liner is effective in addressing the fundamental challenge of low resistivity for the polycrystalline silicon material, leading to better electrical performance of TPVs than TSVs. Parametric studies indicate that thicker sidewall liners result in better electrical performance. A two-dimensional axisymmetric model was established to simulate the first principal stresses in silicon and shear stresses in TPV under thermal cycling. TPVs with thick polymer liners present both smaller principal stresses and shear stresses than TSVs due to the low modulus of polymer. Parametric studies suggest that sidewall liners act as stress buffers and thicker liners result in better mechanical performance. Design guidelines based on simulation results were used in TPV demonstration and test vehicle fabrication. Fracture strength of polycrystalline silicon panel has been fundamentally studied with four-point bending tool and Weibull plot. Surface polymer liners on both sides were introduced to improve the handling of thin silicon panels. Quantitative study showed higher characteristic fracture strength for the panel with surface liners than raw silicon panel. Low cost and double-side processes have been developed for TPV fabrication including UV (ultraviolet) lasers for TPV formation, double laser method for liner fabrication and electroless Cu for seed formation. Key steps and mechanisms for aforementioned processes were summarized and discussed. Polycrystalline silicon interposers with TPVs and up to four metal RDLs (re-distribution layers) were designed, fabricated and characterized. Measurement results showed low insertion loss for both TPVs and CPW (co-planar waveguide) transmission lines. Good model to hardware correlation was also observed. Reliability test vehicles of polycrystalline silicon interposers were also designed and fabricated for thermal cycling test. TPVs survived 4000 cycles without significant resistance changes. SEM imaging on the cross-section of the samples confirmed no Cu or silicon cracking. Magnified images around corner also suggested good adhesion at Cu/liner and silicon/liner interfaces.
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Terner, Mark Robert. "The production of low-cost α-sialons via carbothermal reduction-nitridation of slag-based mixtures." Monash University, School of Physics and Materials Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9577.
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Hilali, Mohamed M. "Understanding and Development of Manufacturable Screen-Printed Contacts on High Sheet-Resistance Emitters for Low-Cost Silicon Solar Cells." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7284.
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A simple cost-effective approach was proposed and successfully employed to fabricate high-quality screen-printed (SP) contacts to high sheet-resistance emitters (100 ohm/sq) to improve the Si solar cell efficiency. Device modeling was used to quantify the performance enhancement possible from the high sheet-resistance emitter for various cell designs. It was found that for performance enhancement from the high sheet-resistance emitter, certain cell design criteria must be satisfied. Model calculations showed that in order to achieve any performance enhancement over the conventional ~40 ohm/sq emitter, the high sheet resistance emitter solar cell must have a reasonably good (120,000 cm/s) or low front-surface recombination velocity (FSRV). Model calculations were also performed to establish requirements for high fill factors (FFs). The results showed that the series resistance should be less than 0.8 ohm-cm^2, the shunt resistance should be greater than 1000 ohm-cm^2, and the junction leakage current should be less than 25 nA/cm^2. Analytical microscopy and surface analysis techniques were used to study the Ag-Si contact interface of different SP Ag pastes. Physical and electrical properties of SP Ag thick-film contacts were studied and correlated to understand and achieve good-quality ohmic contacts to high sheet-resistance emitters for solar cells. This information was then used to define the criteria for high-quality screen-printed contacts. The role of paste constituents and firing scheme on contact quality were investigated to tailor the high-quality screen-printed contact interface structure that results in high performance solar cells. Results indicated that small particle size, high glass transition temperature, rapid firing and less aggressive glass frit help in producing high-quality contacts. Based on these results high-quality SP contacts with high FFs0.78 on high sheet-resistance emitters were achieved for the first time using a simple single-step firing process. This technology was applied to different substrates (monocrystalline and multicrystalline) and surfaces (textured and planar). Cell efficiencies of ~16.2% on low-cost EFG ribbon substrates were achieved on high sheet-resistance emitters with SP contacts. A record high-efficiency SP solar cell of 19% with textured high sheet-resistance emitter was also fabricated and modeled.
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Lauterbach, Adam Peter. "Low-cost SiGe circuits for frequency synthesis in millimeter-wave devices." Australia : Macquarie University, 2010. http://hdl.handle.net/1959.14/76626.
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"2009"Thesis (MSc (Hons))--Macquarie University, Faculty of Science, Dept. of Physics and Engineering, 2010.
Bibliography: p. 163-166.
Introduction -- Design theory and process technology -- 15GHz oscillator implementations -- 24GHz oscillator implementation -- Frequency prescaler implementation -- MMIC fabrication and measurement -- Conclusion.
Advances in Silicon Germanium (SiGe) Bipolar Complementary Metal Oxide Semiconductor (BiCMOS) technology has caused a recent revolution in low-cost Monolithic Microwave Integrated Circuit (MMIC) design. -- This thesis presents the design, fabrication and measurement of four MMICs for frequency synthesis, manufactured in a commercially available IBM 0.18μm SiGe BiCMOS technology with ft = 60GHz. The high speed and low-cost features of SiGe Heterojunction Bipolar Transistors (HBTs) were exploited to successfully develop two single-ended injection-lockable 15GHz Voltage Controlled Oscillators (VCOs) for application in an active Ka-Band antenna beam-forming network, and a 24GHz differential cross-coupled VCO and 1/6 synchronous static frequency prescaler for emerging Ultra Wideband (UWB) automotive Short Range Radar (SRR) applications. -- On-wafer measurement techniques were used to precisely characterise the performance of each circuit and compare against expected simulation results and state-of-the-art performance reported in the literature. -- The original contributions of this thesis include the application of negative resistance theory to single-ended and differential SiGe VCO design at 15-24GHz, consideration of manufacturing process variation on 24GHz VCO and prescaler performance, implementation of a fully static multi-stage synchronous divider topology at 24GHz and the use of differential on-wafer measurement techniques. -- Finally, this thesis has llustrated the excellent practicability of SiGe BiCMOS technology in the engineering of high performance, low-cost MMICs for frequency synthesis in millimeterwave (mm-wave) devices.
Mode of access: World Wide Web.
xxii, 166 p. : ill (some col.)
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Chen, Tao. "UTILIZATION OF BIO-RENEWABLE LIGNIN IN BUILDING HIGH CAPACITY, DURABLE, AND LOW-COST SILICON-BASED NEGATIVE ELECTRODES FOR LITHIUM-ION BATTERIES." UKnowledge, 2017. http://uknowledge.uky.edu/cme_etds/75.
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Silicon-based electrodes are the most promising negative electrodes for the next generation high capacity lithium ion batteries (LIB) as silicon provides a theoretical capacity of 3579 mAh g-1, more than 10 times higher than that of the state-of-the-art graphite negative electrodes. However, silicon-based electrodes suffer from poor cycle life due to large volume expansion and contraction during lithiation/delithiation. In order to improve the electrochemical performance a number of strategies have been employed, such as dispersion of silicon in active/inactive matrixes, devising of novel nanostructures, and various coatings for protection. Amongst these strategies, silicon-carbon coating based composites are one of the most promising because carbon coating is comparatively flexible, easy to obtain, and scalable with various industrial processes.
Low cost and renewable lignin, which constitutes up to 30% dry mass of the organic carbon on earth, is widely available from paper and pulp mills which produce lignin in excess of 50 million tons annually worldwide. It is a natural bio-polymer with high carbon content and highly interconnected aromatic network existing as a structural adhesive found in plants. Generally burnt for energy on site, lignin is gradually finding its way into high value-added products such as precursor for carbon fibers, active material in negative electrodes, and raw material for supercapacitors.
This dissertation focuses on high performance silicon-based negative electrodes utilizing lignin as the carbon precursor for conductive additive, binder, and carbon coating. To my knowledge this is one of the first works attempting to utilize and summarize the performance of lignin in silicon-based negative electrodes. The first part of the dissertation shows that silicon-lignin composites treated at 800 ºC displayed good capacity and cycling performance. The second part goes to generalize the effect of temperature on silicon-lignin composites and shows that a low temperature treatment granted an electrode with superior performance and cycling properties owing to the preservation of polymeric properties of lignin. The final part of the dissertation discusses the current research trends in SiOx based negative electrodes and extends lignin to that field.
This dissertation will, hopefully, provide knowledge and insight for fellow researchers wishing to utilize lignin or other renewable resources in devising advanced battery electrodes.
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Konijn, Mark. "Multilevel Nanoengineering for Imprint Lithography." Thesis, University of Canterbury. Electrical and Computer Engineering, 2005. http://hdl.handle.net/10092/1071.
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The current trend in pushing photo lithography to smaller and smaller resolutions is becoming increasingly difficult and expensive. Extreme ultra-violet lithography is an alternate method that has the potential to provide feature sizes down to 30 nm, however, it will come at an even greater cost. Nanoimprint lithography (NIL) is another lithographic technique which is promising to provide very high resolutions at a relatively low cost. Imprinting works by using a mold with a surface patterned with the required nano structures and pressing it into a substrate coated with a deformable polymer. Due to its direct pattern replication technique, it is very capable of reproducing three-dimensional structures, however limited research has been performed on this to date. In this study, investigations have been performed into developing a reliable process for creating SiN molds with sub-100 nm structures with variable height control. The process relies on a negative tone electron beam resist which can be patterned to various thicknesses by varying the exposure dosage. This allows for the creation of complex multi-layer structures in a single electron beam lithography step. These patterns then have been transferred into the SiN substrate by a single reactive ion etch. From here the mold is ready for use in imprinting. Study has also been performed into imprinting process as well. This includes the development of an imprint press, the manner in which NIL works. Investigations have been performed into the imprinting performance of 3D molds. Thermal expansion issues have been found and addressed, as have adhesion problems. Some other aspects of 3D NIL which have not been addressed in this study have been outlined in future work for further investigation.
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Stem, Nair. "Células solares de silício de alto rendimento: otimizações teóricas e implementações experimentais utilizando processos de baixo custo." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-02042008-113959/.
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O trabalho realizado nesta tese esteve apoiado em dois objetivos principais. O primeiro centrado na otimização das etapas e processos de fabricação de células solares de silício de alto rendimento envolvendo redução de custos. O segundo objetivo foi direcionado na implementação de células solares eficientes e não dependentes do armadilhamento de impurezas através da difusão de alumínio. Para levar a cabo estes objetivos de forma planejada, o trabalho dividiu-se em otimizações teóricas e implementações experimentais. As otimizações teóricas foram realizadas utilizando dois programas: um programa desenvolvido (simulacell.pas) e implementado no próprio LME (versão 2), e o outro adquirido comercialmente, PC1D. De acordo com os resultados obtidos em estruturas completas n+p e n++n+p foi possível concluir que tanto as estruturas formadas através de emissores homogêneos como as obtidas utilizando emissores duplamente difundidos permitem alcançar eficiências elevadas, 25,5% a 26,0%, respectivamente, em um amplo intervalo de espessuras e concentrações superficiais de dopantes. No que tange aos desenvolvimentos experimentais, este trabalho se inicia com o desenvolvimento de um processo simplificado de baixo custo, em células solares de silício Cz de baixa resistividade com estrutura n+pp+, tipo \"mesa\". Este processo simplificado também está baseado na difusão de fósforo e alumínio (P/Al), utilizando gases industriais e reagentes químicos de grau \"para análise\", como uma transposição do processo de fabricação anteriormente desenvolvido no LME-EPUSP em substratos de silício FZ utilizando tecnologia planar. A célula solar mais representativa do processo implementado, A-16-1, permitiu atingir eficiências no entorno de 17%. As implementações experimentais visaram inicialmente o desenvolvimento de um procedimento visando à qualificação de materiais de partida (silício), utilizando a técnica de decaimento fotocondutivo (PCD) através de dois procedimentos de passivação de superfícies; oxidações térmicas e difusões suaves de fósforo. Posteriormente, utilizando o sistema PCD, novas otimizações dos emissores de tipo n+ homogêneos e regiões de tipo p foram realizadas, seguidos por oxidações térmicas passivadoras hidrogenadas, preservando-se o tempo de vida do volume em valores elevados (aproximadamente 1ms, após a realização de todas as etapas térmicas). Estes resultados qualificam o silício e os materiais de consumo utilizados, assim como, o novo processo de fabricação desenvolvido. Esta técnica também permitiu qualificar os emissores com perfil Gaussianos processados, atingindo valores da ordem de 45fA/cm2 para densidades de recombinação em estruturas n+pn+. Desenvolveram-se também estruturas n+p em materiais Cz de baixa resistividade 2-3W.cm de dois diferentes fabricantes, e silício FZ com 0,5W.cm. Pôde ser comprovada a qualidade das etapas que compõem o processo completo otimizado tendo-se obtido tensões de circuito aberto-implícitas de 652,4mV (Si-Cz fabricante 1) e 662,6mV (Si-Cz fabricante 2), e 670,8mV (FZ). De acordo com simulações realizadas utilizando parâmetros habituais de dispositivos do próprio LME, estas tensões, quando associadas a um conjunto óptico frontal típico das células solares de alto rendimento do LME (texturização química aleatória e filme de SiO2), permitirão atingir valores entre 19% - 20%. Entretanto, utilizando texturização e camada dupla torna-se plausível atingir o marco de 21% de rendimento, ultrapassando assim a barreira dos 17% (recorde nacional), e comprovando a potencialidade da infra-estrutura deste laboratório para o desenvolvimento de células solares não dependentes do efeito do armadilhamento de impurezas através da difusão de alumínio.The work developed at this thesis has been based on two main objectives. First, it was focused on the optimization of the steps and processes for the fabrication of high efficiency solar cells, reducing production costs. The latter objective was directed to develop solar cells that were efficient and non-dependent on impurities gettering performed through the aluminum diffusion. In order to attend the planned objectives the work was divided into the theoretical objectives and experimental developments. The theoretical optimizations were performed using two different program codes: one was developed at LME (simulacell.pas), being upgraded afterwards (version 2); and the other was acquired commercially, the PC1D. According to the obtained results in complete structures n+p and n++n+p, it was possible to conclude that the homogeneous and double diffused emitter structures can provide high efficiencies, from 25,5% to 26,0%, respectively, for a wide range of thicknesses and surface doping levels. Concerning the experimental developments, this work starts with a low cost simplified process, using Cz silicon solar cells with low base resistivity and the structure n+pp+, \"mesa\" type. This simplified process was also based on the phosphorus/ aluminum diffusion (P/Al), using industrial gases and for analysis grade chemical reagents, as a fabrication process transposition of the process previously developed at LME-EPUSP using silicon substrates with planar technology. The most representative solar cells of the implemented process, A-16-1, provided about a 17% efficiency. The experimental implementations aimed the development of procedure for starting material (silicon) qualification, by using the photoconductive decay technique (PCD) with two surface passivation procedures: thermal oxidation and light phosphorus diffusion. Later, using PCD system, new optimizations of n+ homogeneous emitters and p-type region were performed, followed by passivating thermal oxidations with hydrogenation, maintaining the volume lifetime at high values (approximately 1ms, after each thermal step). These results qualified the used silicon and the consumer materials, as well the new fabrication process developed. This technique has also allowed qualifying the processed Gaussian profile emitters, providing values about 45fA/cm2 for the recombination current density in n+pp+ structures. N+p structures were also developed using Cz silicon with low resistivity 2- 3W.cm of two different manufacturers and FZ with 0.5W.cm. It could be proved the quality of the steps of a complete optimized process resulting implicit open circuit voltages of 652.4mV (Cz silicon - manufacturer type 1), 662.6mV (Cz silicon - manufacturer type 2), and 670.8mV (FZ silicon). According to the theoretical simulations performed using the usual parameters of devices processed at LME (random chemical texturization and SiO2 film), efficiencies between 19%-20% can be reached. However, using a random texturization and a double layer anti-reflection system, a 21% efficiency becomes possible, surpassing the 17% barrier (national record), and proving the potentiality of this laboratory facility for the development of solar cells non-dependent on impurity gettering through the aluminum diffusion.
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Hayes, Maxim. "Intégration de collecteurs de charges avancés dans les cellules solaires bifaciales à haut rendement : vers un procédé générique pour les nouveaux matériaux silicium." Electronic Thesis or Diss., Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0519.
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L'industrie PV connaît un fort engouement pour les cellules PERC. Néanmoins leurs performances sont limitées par deux sources de recombinaison des porteurs de charge: au niveau de l'émetteur obtenu par diffusion de P, et en face arrière aux interfaces Al-Si. L'objectif principal de cette thèse vise à limiter ces pertes en intégrant deux nouveaux collecteurs. Le premier est un émetteur sélectif (ES) obtenu par implantation ionique à immersion plasma (PIII) de P. Le second concerne un contact passivé (CP) constitué d'un film de silicium polycristallin (poly-Si) dopé au B sur un oxyde mince. Dans un second temps, les travaux s'intéressent à la compatibilité entre ces collecteurs et les plaquettes de Si issues de lingots fabriqués par solidification dirigée. Un procédé de masquage in situ des implantations PIII a permis d'élaborer des ES avec une bonne maîtrise de la géométrie du motif et des niveaux de dopage. Ensuite, un éventail de techniques pour la métallisation du poly-Si(B) a été étudié. La voie de métallisation par sérigraphie de pâtes traversantes est la plus encourageante à l'heure actuelle. Elle permet l'utilisation de couches hydrogénantes non sacrificielles qui ont mené à l'obtention de précurseurs de cellules avec un excellent niveau de passivation. Néanmoins, la résistance de contact entre le métal et le poly-Si(B) demeure à ce jour trop élevée pour une intégration optimale. Enfin, l'association de Si multicristallin avec différents CP a montré la propension de ces derniers à générer un effet getter externe efficace. Cela laisse envisager une très bonne compatibilité entre l'architecture cellule développée et les Si bas-coût et à faible emprunte carboneThanks to a relatively simple fabrication process and high conversion efficiency values the PERC structure is well established at the industrial level. Nevertheless, industrial PERC solar cells performances are mostly limited by two charge carrier recombination sources: P thermally diffused emitter on the front side and the Al-Si interfaces at the rear contacts. The main goal of this work aims at limiting both recombination sources. A selective emitter (SE) obtained by plasma immersion ion implantation (PIII) is developed for an integration on the front side; whereas a B-doped polysilicon (poly-Si) on oxide passivated contact (PC) is integrated on the back side. The second goal of this work consists in evaluating the compatibility between these advanced carrier collectors and directionally solidified Si materials. SE featuring good geometrical properties and a well-controlled doping were fabricated thanks to an in situ localized doping process obtained with a specific mask developed for PIII. Besides, several metal deposition technologies were investigated for the poly-Si(B). Fire-through screen-printing appears as the most promising approach so far. Indeed, the deposition of a non-sacrificial hydrogen-rich layer allowed to reach an excellent surface passivation level for solar cell precursors. However, the specific contact resistivity obtained remains too high for an optimal cell integration. Lastly, the fabrication of poly-Si PC showed excellent external gettering efficiencies for multicrystalline Si. Thus, the potential of the developed cell structure to be integrated with low-cost and low carbon footprint materials is encouraging
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Zayyoun, Najoua. "Optimisation et modélisation du détachement de couches minces de silicium par contrainte thermique avec ou sans guidage de la fracture : application au photovoltaïque." Thesis, Orléans, 2019. http://www.theses.fr/2019ORLE3036.
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La réduction des coûts de production des cellules photovoltaïques et l'augmentation de leur rendement de conversion présentent aujourd’hui un fort intérêt technologique et écologique pour répondre aux problèmes de changement climatique engendrés par les énergies fossiles (charbon, pétrole et gaz naturel). La motivation de cette thèse est l’étude des procédés innovants de production de couches ultra-minces de silicium monocristallin de plusieurs centaines de nanomètres à plusieurs dizaines de micromètres d’épaisseur, basés sur les contraintes thermiques et l’implantation d’hydrogène à basse énergie. Le détachement des couches ultra-minces de silicium se fait sans perte de matière première, permettant ainsi de réduire la consommation du silicium afin de produire des cellules photovoltaïques à bas-coûts.Dans ce travail, nous avons tout d’abord déterminé par modélisation analytique et numérique les contraintes permettant le détachement du silicium par contraintes induites « Controlled-Spalling » et prédit l’épaisseur détachée des couches minces de silicium. Les modèles proposés dépendent des paramètres thermiques et élastiques des matériaux utilisés et de chargement thermique appliqué. Un bon accord entre les résultats théoriques et expérimentaux a été obtenu. Nous avons ensuite étudié les paramètres optimaux conduisant au détachement des films de silicium, à savoir l’épaisseur et la nature du substrat contraignant ainsi que l’épaisseur de la colle. Par la suite, des essais de détachement du silicium par contraintes induites guidé par l’implantation d’hydrogène ont été réalisés. Des caractérisations expérimentales et des simulations FEM des contraintes thermiques induites dans le silicium implanté à différents stades de recuits ont été faites permettant de comprendre les mécanismes mis en jeu lors du détachement du silicium fragilisé. Ensuite, des mesures par différentes techniques (Spectroscopie Raman, Profilomètre optique, MEB, Microscope optique numérique) des contraintes résiduelles et de la rugosité des films détachés par le procédé « Controlled-Spalling » ont été réalisées pour explorer les pistes conduisant à l’amélioration de la qualité de ces filmsThe reduction of photovoltaic cells cost and the increase of their efficiency is probably one of the best solution to tacle the climate change issues. The mean of this thesis is to study the innovative processes to produce ultra-thin monocrystalline silicon layers without loss of raw material (with thicknesses ranging from several hundred nanometers to several micrometers), by using thermal stress and low energy hydrogen implantation. The use of such kerf-free processes leads to a significant reduction of the silicon consumption, in order to produce of low-cost photovoltaic solar cells.In this work, by using analytical and numerical modeling, we first determined the thermal stresses needed for the detachment of silicon by stress-induced spalling process and predicts the detached thickness of silicon foils. These models depend on thermals and elastics parameters of metal used as well as the applied thermal loading. A good agreement between the theoretical and experimental results was obtained. Furthermore, different optimal parameters leading to the detachment of silicon foils with desired thicknesses using SIS process were investigated such as the thickness of the stressor layer, the nature of stressor layer and the thickness of glue. In a second part, thin silicon layers were transferred as a function of thermal annealing using the stress-induced spalling process guided by hydrogen implantation-induced defects. Then, the use of experimental characterizations and FEM simulations of the thermal stresses induced in implanted silicon we explain the mechanisms involved when combining the two processes. Characterization of silicon foils was performed by various technique in order to validate and optimized the process
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Alam, Mahmood. "Development of vacuum insulation panel with low cost core material." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/11658.
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Buildings consume around half of the UK's total energy consumption and are responsible for almost 50% of UK's total carbon dioxide (CO2) emissions. Use of high thermal resistance insulation in buildings is critical to save the substantial amounts of space heating energy lost through building fabric. Conventional building insulation materials have higher thermal conductivity values ranging from 40 mWm-1K-1 (Glass fibre) - 26 mWm-1K-1 (Polyurethane foam) and require larger thicknesses to achieve stringent building regulation requirements which may not be feasible due to techno-economic constraints. Vacuum Insulation Panel (VIP) is a relatively new insulation for building applications that offers 5-8 times higher thermal resistance and can achieve significant space savings in buildings. VIPs are produced as a rigid panel comprising inner core board laminated in an outer high barrier envelope under evacuated conditions (< 5mbar). However, the main challenge for large scale acceptance of VIPs in building applications is their higher cost. VIPs have been shown to have an approximately 10 times longer payback compared to conventional EPS insulation due to their high initial cost. Expensive materials currently being used for VIP manufacturing such as fumed silica contribute to high cost of VIPs and it is critical to identify alternative low cost materials for VIP components to overcome the challenge of high cost. The aim of this thesis was to develop an alternative low cost material and investigate its suitability for use as VIP core. Expanded perlite, a low cost material was identified as a replacement of expensive fumed silica in a VIP core. Composite samples containing expanded perlite, fumed silica, silicon carbide (SiC) and polyester fibres were developed by dry mixing of the constituents in different mass ratios and their different properties were experimentally measured to identify optimum composition of composite. Gaseous thermal conductivity at different pressures was calculated from the pore size data obtained using Mercury Intrusion Porosimetry (MIP), gas adsorption and electron microscopy. Radiative conductivity of composite samples was measured using Fourier Transform Infrared (FTIR) to ascertain the opacifying effect of expanded perlite and opacifier (SiC). Centre of panel thermal conductivity of core boards of size 100mm x 100mm made of composite material at atmospheric pressure was measured by using a small guarded hot plate device. Average pore diameter values of expanded perlite decreased with the partial filling of fumed silica aggregates and was found to be in the range of 150-300 nm yielding lower gaseous conductivity values of 1.2-2.1 mWm-1K-1 at 100mbar and became negligible upon further decreasing pressures below 10 mbar. Core boards made of optimised composite containing 30% expanded perlite and 50% fumed silica along with SiC and polyester fibres was found to achieve centre of panel thermal conductivity of 28 mWm-1K-1 at atmospheric pressure and the average radiative conductivity of 0.67 mWm-1K-1 at 300K with its gaseous thermal conductivity at 1 mbar being 0.016 mWm-1K-1. According to the results of the thesis VIP prototypes consisting of core made with optimised composite consisting (50 mass% of fumed silica, 30 mass% of expanded perlite along with 8 mass% of fibre and 12 mass% of SiC) yielded centre of panel thermal conductivity of 7.4-7.6 mWm-1K-1 at pressure of 0.53-0.64 mbar. Opacifying properties of expanded perlite were observed and quantified. Expanded perlite reduced the radiative conductivity of the composite requiring smaller quantities of high density opacifiers such as SiC. For sample containing no expanded perlite, average radiative conductivity was calculated to be 1.37 mWm-1K-1 and radiative conductivity values decreased to 1.12 mWm-1K-1, 0.67 mWm-1K-1, 0.63 mWm-1K-1 and 0.50 mWm-1K-1 with mass ratio of expanded perlite 20%, 30%, 40% and 60% respectively. It was concluded that the solid conductivity of prototypes VIPs was 1.8-2 times higher compared to those of commercially available VIPs and is the main reason for higher centre of panel thermal conductivity.
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PIETRICOLA, GIUSEPPE. "Waste valorization trough dehydrogenase enzymes immobilized on low-cost inorganic supports." Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2969232.
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Schunemann, Esteban. "Paste deposition modelling : deconstructing the additive manufacturing process : development of novel multi-material tools and techniques for craft practitioners." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/13803.
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A novel paste deposition process was developed to widen the range of possible materials and applications. This experimental process developed an increasingly complex series of additive manufacturing machines, resulting in new combinations of novel materials and deposition paths without sacrificing many of the design freedoms inherit in the craft process. The investigation made use of open-source software together with an approach to programming user originated infill geometries to form structural parts, differing from the somewhat automated processing by 'closed' commercial RP systems. A series of experimental trials were conducted to test a range of candidate materials and machines which might be suitable for the PDM process. The combination of process and materials were trailed and validated using a series of themed case studies including medical, food industry and jewellery. Some of the object created great interest and even, in the case of the jewellery items, won awards. Further evidence of the commercial validity was evidenced through a collaborative partnership resulting in the development of a commercial version of the experimental system called Newton3D. A number of exciting potential future directions having been opened up by this project including silicone fabrics, bio material deposition and inclusive software development for user originated infills and structures.
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Magnant, Jérôme. "Composites fibreux denses à matrice céramique autocicatrisante élaborés par des procédés hybrides." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14105/document.
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L'élaboration de composites à matrice céramique denses et à fibres continues multidirectionnelles par de nouveaux procédés hybrides a été étudiée. Les procédés développés reposent sur le dépôt d'interphases autour des fibres par Infiltration Chimique en phase Vapeur (CVI) puis sur l'introduction de poudres céramiques au sein de préformes fibreuses par infusion de suspensions aqueuses colloïdales concentrées et stables, et enfin sur la consolidation des préformes soit par frittage flash, soit par imprégnation réactive de métaux liquides.La consolidation des composites par frittage flash est très rapide (palier de maintien en température inférieure à 5 minutes) et permet d'obtenir des composites denses. Durant le frittage, la dégradation des fibres de carbone a pu être évitée en adaptant le cycle de pression afin de limiter l'évolution des gaz au sein du système.La densification totale des composites par imprégnation de métaux liquides a été obtenue en contrôlant attentivement les paramètres d'imprégnation afin d'éviter de piéger des espèces gazeuses au sein des préformes fibreuses.Les composites à fibres de carbone consolidés par frittage flash ou par imprégnation réactive de métaux liquide possèdent un comportement mécanique de type élastique endommageable ainsi qu'une contrainte à rupture en flexion voisine de 300 MPa. Ces composites ont montré leur capacité à s'autocicatriser dans des conditions oxydantes. Comparés aux composites à matrice céramiques élaborés par CVI, les composites densifiés par imprégnation de métaux liquide sont eux parfaitement denses et ont un comportement mécanique en traction à température ambiante similaire avec notamment une contrainte à rupture en traction de 220 MPaThe fabrication of multidirectional continuous carbon fibers reinforced dense self healing Ceramic Matrix Composites by new short time hybrid processes was studied. The processes developed are based, first, on the deposition of fiber interphase and coating by chemical vapor infiltration, next, on the introduction of ceramic powders into the fibrous preform by Slurry Impregnation and, finally, on the densification of the composite by liquid-phase Spark Plasma Sintering (SPS) or by Reactive Melt Infiltration of silicon (RMI).The homogeneous introduction of the ceramic particles into the multidirectional fiber preforms was realized by slurry impregnation from highly concentrated (> 32 %vol.) and well dispersed aqueous colloid suspensions. The densification of the composites by spark plasma sintering was possible with a short (< 5 minutes) dwelling period in temperature. The chemical degradation of the carbon fibers during the fabrication was prevented by adapting the sintering pressure cycle to inhibit gas evolution inside the system. The composites elaborated are dense. The fully densification of the composites by RMI was realised by carefully controlling the impregnation parameters to avoid to entrap some gaseous species inside the fiber preforms. Our carbon fiber reinforced ceramic matrix composites processed by Spark Plasma Sintering or Reactive Melt Infiltration have a damageable mechanical behaviour with a room temperature bending stress at failure around 300 MPa and have shown their ability to self-healing in oxidizing conditions. Compared to the CMC processed by CVI, the composites processed with a final consolidation step by RMI are fully dense and have a similar room temperature tensile test behaviour with an ultimate tensile stress around 220 MPa
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Shih, Yu-Pei, and 施郁霈. "Recycling and Analytical Technologies of Silicon Sawing Waste and the Recovered Silicon for Low-Cost Applications." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/j3ut8h.
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博士國立臺北科技大學
工程學院工程科技博士班
105
In a country producing silicon wafer, an important policy of waste reduction is to recycle the resource from silicon ingot sawing waste. In addition to metals impurities, a large amount of reusable Si, SiC and glycol solution are found in the sawing waste. Effective recycling of silicon sawing waste and innovative applications must improve the circular economic value of the wafer manufacturing system. First of all, this study adopted gravity settling or centrifugation to recover glycol solution and analyzed the feasibility of recycling technologies. The experimental results show that adding different solvents is related to the quality of final recycled glycol solution. In quantification of Si and SiC, several ways to describe the composition of Si and SiC were compared. In addition, acid treatment was applied to remove metal impurities from silicon sawing waste. The effects of acidic species, concentration and ratio of solid to liquid on Fe dissolution and the dissolution kinetics were investigated. Moreover, the vertical sedimentation system was utilized to separate Si and SiC. The difference between the experimental results and theoretical calculation was discussed. Furthermore, an idea about the potential of hydrogen energy generation from silicon and the applications of silicate produced from Si-water reaction were presented. First, the influence of particle size, alkali solution concentration, and reaction temperature were studied and its kinetic mechanism for Si-water reaction was proposed. On the one hand, the silicate solution was used to prepare an adsorbent and to remove nickel ions from wastewater. Analysis of experimental data indicated that the pseudo-second order kinetics and Langmuir model could well describe the adsorption process. On the other hand, the silicate solution was used to prepare gelled electrolytes by sulfuric acid titrating and to apply on the lead redox reaction. In summary, this study are included that the Si and SiC quantitation, techniques regarding solid-liquid, solid-solid separation, metal removal, hydrogen production from silicon and applications of silicate solution. After solid-liquid separation, high-quality glycol solution was obtained; the metal impurities can be dissolved and removed by acids. Using sedimentation, the Si-rich or SiC-rich powders were obtained. The recovered Si could apply to hydrogen evolution, and then the silicate solution or high-purity SiC were reused. Simple, low-cost recycling processes and strategies encourage companies to adopt them and this study benefits the analysis, reduction, reuse and zero-emission of silicon sawing waste.
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Nassar, Joanna M. "Transformational Electronics: Towards Flexible Low-Cost High Mobility Channel Materials." Thesis, 2014. http://hdl.handle.net/10754/316698.
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For the last four decades, Si CMOS technology has been advancing with Moore’s law prediction, working itself down to the sub-20 nm regime. However, fundamental problems and limitations arise with the down-scaling of transistors and thus new innovations needed to be discovered in order to further improve device performance without compromising power consumption and size. Thus, a lot of studies have focused on the development of new CMOS compatible architectures as well as the discovery of new high mobility channel materials that will allow further miniaturization of CMOS transistors and improvement of device performance.
Pushing the limits even further, flexible and foldable electronics seem to be the new attractive topic. By being able to make our devices flexible through a CMOS compatible process, one will be able to integrate hundreds of billions of more transistors in a small volumetric space, allowing to increase the performance and speed of our electronics all together with making things thinner, lighter, smaller and even interactive with the human skin. Thus, in this thesis, we introduce for the first time a cost-effective CMOS compatible approach to make high-k/metal gate devices on flexible Germanium (Ge) and Silicon-Germanium (SiGe) platforms.
In the first part, we will look at the various approaches in the literature that has been developed to get flexible platforms, as well as we will give a brief overview about epitaxial growth of Si1-xGex films. We will also examine the electrical properties of the Si1-xGex alloys up to Ge (x=1) and discuss how strain affects the band structure diagram, and thus the mobility of the material. We will also review the material growth properties as well as the state-of-the-art results on high mobility metal-oxide semiconductor capacitors (MOSCAPs) using strained SiGe films.
Then, we will introduce the flexible process that we have developed, based on a cost-effective “trench-protect-release-reuse” approach, utilizing the industry’s most used bulk Si (100) wafers, and discuss how it has been used for getting flexible and semi-transparent SiGe and Ge platforms.
Finally, we examine the electrical characteristics of our materials through the fabrication of high-k/metal gate MOSCAPs with SiGe and Ge as channel material. We present their electrical performance on both non- flexible and flexible platform and discuss further improvement that has to be made in order to get better behaving devices for future MOSFET fabrication.
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Hao-YuLi and 李昊宇. "High-Efficiency Thin-Film Silicon Solar Cell with Low-Cost Improved Back Electrode." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/52133501103735262139.
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碩士國立成功大學
電機工程學系碩博士班
100
Back electrode plays a very key role in solar cells; in this dissertation, we produce a back electrode of thin-film silicon solar cell, aiming at a lower cost to replace the traditional back electrode. The experiment is divided into two parts; the first part, we use the RF magnetron sputtering method to deposit the transparent conductive film AZO (ZnO: Al) of the back electrode with various process parameters, in order to achieve the best resistivity and transmittance, in the second, we are in accordance with traditional back electrode for improvement. Most of the conventional back electrode of solar cells consist of the transparent conductive film and a metal electrode (usually Ag) coupled with the metal protective layer (Al or Ti). Here we use thin Ag layer with thickness reducing from 200~250nm to 30~50nm, and coated with PDR (Pigmented Dielectric Reflector) to replace Ti. PDR is a paint-like coating of white glue mixed with nano-TiO2 particles. The white paint is aimed at reducing costs and improving Fabry-Pe'rot interference by high reflectance and scattering power of the white paint to enhance external quantum efficiency. In AZO experiments, we investigate three sets of parameters including substrate temperature, sputtering power, and working pressure. The results show that at high substrate temperature, high sputtering power and low working pressure, the AZO film of thickness 100nm has the lowest resistivity of 6.4 × 10-3Ω.cm, and the transmittance in the visible light reaches more than 80%. In white paint experiment, we measure the reflectance and the Haze of the films with three different particle size (135nm, 230nm, 320nm) and solid content (12%, 15%, 20%) of white paint, and then coat the white paint on the solar cell to measure IV and the QE. The results show that all the white paint can enhance the QE and improve Fabry-Pe'rot interference , in particular, the white paint with the particle size 135nm under Ag50nm has the most profound effect likely due to the smallest particle size has the best scattering efficiency.
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Seren, Sven [Verfasser]. "Low cost solar cells from fast grown silicon ribbon materials / vorgelegt von Sven Seren." 2007. http://d-nb.info/985284579/34.
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Huang, Ya-Tza, and 黃雅慈. "Formation of transparent thin metal/silicon interface layers for improving the performance of silicon solar cells prepared with a low cost and low hazardous process." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/12281421022853607989.
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碩士國立臺灣海洋大學
光電科學研究所
103
A recent report from S. C. Tseng et al. published on Energy &; Environmental Sciences 4, 5020–5027 (2011) has shown that thermal evaporation of gold film on a Si susbstrate followed by removal of the gold film through adhesive tapes will leave on the Si surface a thin (few nm) gold layer, or more specifically, a gold/silicon interface layer. The interface layer is not only transparent, but is also of good ohmic contact. In this thesis, we discovered a variety of ways to form transparent ohmic-contact interface layers within gold/silicon or silver/silicon interface on the pyramidic or planar surface of silicon; and, we successful applied the interface layers to solar cells prepared earlier in our laboratory using a green, low cost, and low hazardous process. Experimental results show that (1) sputtering metal (gold) films followed by removal using adhesive tapes, (2) sputtering metal (gold and silver) films followed by chemical etching, and (3) sintered screen printed silver paste followed by chemical etching, can all form thin layers of transparent metal/silicon interface layer with good ohmic contacts. The application of the above processes however show that the formed thin interface layer did form ohmic contacts, but the thickness of the layer was too thin to have a low-enough series resistance. As a result, the conversion efficiencies of the solar cells were low. To address this issue, we tried to deposit a transparent of indium tin oxide (ITO) conductive layer on the electrode of the interface layer to reduce its series resistance. The results show that the ITO deposition did help recovering the solar cell efficiencies by reducing the series resistance. We believe that if the processes can be further optimized in the future, the originally front electrodes covering 5% to 10% the cell area, is expected to allow additional light enhance, resulting in improved efficiencies of the solar cells.
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Shen, Sheng-Chieh, and 沈聖傑. "Metal-Insulator-Semiconductor Schottky Diode-Type Low Cost Solar Cell with Low Temperature Poly-silicon (LTPS) on Glass Substrate." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/14656673209482296248.
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碩士國立成功大學
電機工程學系碩博士班
96
This thesis reported to fabricate Metal-Insulator-Semiconductor (MIS) Schottky diode-type low cost solar cell with excimer laser annealed (ELA) low temperature poly-silicon (LTPS) on glass substrate. In the cell, the TiO2 thin film was employed as insulator layer. We investigated physical and optical characteristics of the LTPS and TiO2 thin films by FE-SEM, AFM, Hall measurement, XRD, and Spectra Pro500.In addition, the HP4145 was employed for measurement of current gain, Jsc, Voc, fill factor and efficiency. The electrical characteristics of the LTPS thin films were improved by B2H6 and PH3 plasma annealing with PECVD, and found the B2H6 plasma treatment could improve a better optical characteristic than that with PH3 plasma annealing. After plasma annealing, TiO2 thin films were grown on LTPS thin films by radio-frequency sputtering. Then annealed the TiO2 thin film for 10 minutes to improve the quality of the thin film, consequently, the optical gain was raised from 32 to 120. The typical performances of the solar cell with a comb contact electrode (space=200μm), are conversion efficiency =0.05%, Isc= 0.226mA, Voc= 14.5mV, FF =0.82. However, the plasma annealing was changed to a finger structure (space=100μm), the performances were improved to conversion efficiency =3.34%, Isc=1.32 mA, Voc= 230mV, FF =0.576. It is expected the conversion efficiency can be raised to 5〜6%,if the space of the finger contact can be reduced to less than 1μm.
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Chen, Sian-Ren, and 陳咸任. "Effect of surface passivation treatments on silicon solar cells prepared in a green, low-hazardous, and low-cost way." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/62422781383934457806.
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碩士國立臺灣海洋大學
光電科學研究所
103
In this study, we successful improved the efficiency and short circuit current of solar cells prepared in a green process. Developed earlier in our laboratory, this green process uses only KOH instead of deadly HF in removal of PSG layer and dead layers. It incorporates an n-type spin-on diffusion source prepared using a simple sol-gel process. The waste produced during the green process can also be turn into fertilizer; Hence, this is a low cost, low-hazardous green process. Three surface passivation techniques were test in this study, which includes (1) rapid thermal oxidation in air atmosphere, (2) thermal furnace oxidation in oxygen, and, (3) atmospheric-pressure plasma treatment using nitrogen. The purpose of passivation mainly hopes that dangling bonds or defect in Si, if there is, can be compensated to decrease the recombination rates. According to the experimental data, these three techniques do all help enhance the cell efficiencies. Among them, rapid thermal oxidation in air atmosphere at 800℃ under 10 minutes showed the best performance, showing a 33% increase in efficiency (from 9.63% to 12.81%), and a 16.57% Jsc increase from 28.65mA/cm2 to 33.40mA/cm2, compared to the control sample. Performances of thermal furnace oxidation in oxygen are no as expected, which we think the large thermal budget could be responsible. The passivation performance of the atmospheric-pressure plasma treatment using nitrogen, was also not as good as expected, which could be due to the low temperature process not able to passivate the dangling bond between Si and silicon oxide. Finally, we tried to deposit TiO2 as the antireflection layer in order to further reduce the surface reflection for improved efficiencies. However, we found from SEM analysis that TiO2 layers thus deposited were not conformal along the surface of the Si pyramids. In this regard, we recommend the use of the atomic layer deposition (ALD) technique for this TiO2 anti-reflection layer.
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Shiu, Jeng-Yan, and 許正彥. "Improving the efficiency of low-cost metallurgical silicon solar cells by amorphous Si gettering technique." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/17440932492921204725.
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碩士中原大學
電子工程研究所
97
This study investigated for upgraded metallurgical grade silicon (UMG-Si) substrates by gettering process and expected to improve the device’s electronic properties. After gettering process, we develops polycrystalline silicon solar cell by this UMG-Si substrates. In recent years, the demand of solar cells was increasing in the world, which causes the deficiency of silicon feedstock and therefore makes the cost of silicon raw material remain high. So, the aim of this experiment is to reduce cost of material, low cost upgraded metallurgical grade silicon (UMG-Si) wafers will be used as the substrates and an epitaxial amorphous Si (a-Si：H) thin film will be grown thereon by Plasma-enhanced chemical vapor deposition(PECVD) . Loose structure of amorphous Si thin film has many cavities or dislocations that will trap the metal impurities by thermal annealing treatment. The gettering process could improve the electrical properties of UMG-Si substrate. In analytical part, using Hall Measurement, we discuss the improvement of moility after gettering process. In order to understand the metallic impurities characteristic of the substrate which are trapped, we exhibited the metal impurities distribution of substrate by secondary ion mass spectroscopy(SIMS). Then we made solar cell by this substrate. Forming P-N Junction by high temperature diffusion furnace chamber、fabricating front side electrode by E-gun evaporator、rear side electrode by Al paste screen printing、making anti-reflection coating(ARC) by PECVD. We finish solar cell and measure the conversion efficiency.
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Ghanbarzadeh, Sina. "High Performance, Low Cost Lateral Metal-Semiconductor-Metal Photodetector for Large Area Indirect X-Ray Imaging." Thesis, 2013. http://hdl.handle.net/10012/8023.
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The most promising technology for radiography is active matrix flat panel imaging systems (AMFPI). However, AMFPI systems are relatively expensive in comparison with conventional computed radiography (CR) systems. Therefore for general radiography applications low cost systems are needed, especially in hospitals and healthcare systems of the developing countries. The focus of this research is the fabrication and characterization of a low cost amorphous silicon metal-semiconductor-metal photodetector as a photosensitive element in a AMFPI systems. Metal-Semiconductor-Metal photodetectors (MSM-PD) are attractive as sensors due to their ease of fabrication and compatibility with thin film transistor fabrication process primarily because there is no p+ doped layer in comparison with conventional p-i-n photodiodes. We have reported low dark current lateral a-Si MSM-PD (lower than 20pA/mm2 ) with responsivity of 280mA/W and EQE of 65 percent to green light ( l = 525nm). These improvement are achieved by introduction of a PI blocking layer and operating the device at high electric field (15 V/µm). This new structure eliminates the need of p+ and n+ layers which makes this structure fully compatible with the a-Si:H TFT fabrication process and consequently a low cost flat panel imager. Further, in this study we have investigated the effect of the spacing and width of the comb structure in the proposed lateral a-Si MSM-PD to determine the best configuration. Moreover, a-Si MSM-PD with PI blocking layer shows a linear behaviour to the photon flux in the wide range of 200nW/cm2 - 300µW/cm2 intensity of the incoming light. In comparison to vertical p-i-n structures, the reported MSM lateral device shows gains in terms of dynamic range, ease of fabrication (no p+ layer) without any deterioration in EQE and responsivity. This results are promising and encourage the development of a-Si lateral MSM-PD for indirect conversion large area medical imaging applications and especially low cost flat.
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Lin, Kung-Cheng, and 林宮正. "Characterization and Preparation of Low Temperature Poly-silicon (LTPS) Thin Film Metal-Insulation-Semiconductor Schottky Diode-Type Low Cost High Sensitivity Hydrogen Sensors." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/00055386978541801699.
Full textAbstract:
碩士國立成功大學
微電子工程研究所碩博士班
95
In this thesis, we used the excimer laser annealing(ELA) prepare low temperature poly-silicon thin film on glass substrate to fabricate the MIS Schottky diode-type low cost and high sensitivity hydrogen sensors. The experimental results show the Pd/TiO2/Si MIS Schottky diode has the highest sensitivity (2500%), fast response time τr (36sec), good reliability, and selectivity under 1V reverse bias and 100ppm hydrogen. Besides, we improved the property of poly-silicon thin film with Phosphorous doping, Boron doping, and nitrogen plasma treatment, and find the Phosphorous doping gains the best improvement. Moreover, a rough surface in poly-Si thin film can enhances the sensitivity. Furthermore, we find the sensor operated in a high temperature got fast time response, but lowers sensitivity at the same time.
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Amouzgar, Mahmoud. "A Study of New Low-Cost Fabrication Methods of Micro- and Nano-scale Building Blocks for Crystalline Silicon Solar Cells." Thesis, 2013. http://spectrum.library.concordia.ca/977676/1/Amouzgar_PhD_F2013.pdf.
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Energy is the number one problem facing humanity today. Solar cells can capture and transform clean and abundant solar energy into electricity. However, their efficiency must increase and their material and fabrication costs must decrease in order for them to be considered as a viable alternative to the fossil fuels. This research explores and studies new methods for fabricating silicon micro- and nano-scale structures in an economical way as building blocks for crystalline silicon solar cells to lower their overall manufacturing cost while increasing their overall efficiency.
A novel cost-effective approach was proposed and studied for texturing the crystalline silicon using the gas lift effect (GLE). The new proposed method takes advantage of the generated bubbles to create a gas lift effect that increases the surface wetability and removes undesired gas bubbles during the texturing process. This technique requires 50% less chemicals and 60% shorter etching time to achieve the same reflectivity.
Modeling and simulation techniques were used to investigate and elucidate the fluid flow patterns inside the silicon texturing system operating under the new GLE approach. The simulation tool validated the correlation of the lower fluid velocity with the reduced surface coverage, uniformity and subsequently less optimal surface reflectivity. Various inlet designs were modeled and evaluated using a simulation tool for optimal performance. The best inlet design was fabricated and tested resulting in the validation of the simulation work and significant improvement in the GLE texturing system performance.
Two solar cell devices, one based on the novel GLE texturing approach, and the other based on the conventional method, were designed, fabricated and characterized. The application of the new GLE texturing approach resulted in considerable improvements in overall power efficiency of silicon solar cells without any additional increase to the production cost.
Micro and nano structures can enhance optical absorption characteristics and help with providing a more direct path for charge transport to the contacts resulting in an increased overall efficiency. An array of silicon micro-rods with nano-tip was fabricated through a novel low cost multistage approach. The transformation of the pyramid-covered silicon surface to the array of free-standing micro-rods with nano-tip as well as their growth mechanism was investigated. At lower than 80% pyramid coverage, the number of nanostructures dropped dramatically and no nano-structures were obtained at low surface coverage values of less than 50%.
Transparent conductive films (TCFs) can be a viable low-cost alternative to the expensive Indium Tin Oxide (ITO) used in solar cells. A novel thermoplastic nanocomposite of copper nanowires and polymethylmethacrylate was developed by solution mixing technique. Thin films of highly conductive nanocomposites were fabricated by solution casting. This investigation demonstrated that the addition of electric conductive nanoscale fibers to a polymer solution at low concentration levels can transform the plastic to highly conductive phase while maintaining an acceptable transparency of about 55%.
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Onyegam, Emmanuel U. "Remote plasma chemical vapor deposition for high efficiency heterojunction solar cells on low cost, ultra-thin, semiconductor-on-metal substrates." Thesis, 2014. http://hdl.handle.net/2152/30500.
Full textAbstract:
In the crystalline Si solar cell industry, there is a push to reduce module cost through a combination of thinner substrates and increased cell efficiency. Achieving solar cells with sub-100 µm substrates cost-effectively is a formidable task because such thin substrates impose stringent handling requirements and thermal budget due to their flexibility, ease of breakage, and low yield. Moreover, as the substrate thickness decreases the surface passivation quality dictates the performance of the cells. Crystalline Si heterojunction (HJ) solar cells based on hydrogenated amorphous silicon (a-Si:H) have attracted significant interest in recent years due to their excellent surface passivation properties, potential for high efficiency, low thermal budget and low cost. HJ cells with ultra-passivated surfaces showing > 700 mV open-circuit voltages (Voc) and > 20% conversion efficiency have been demonstrated. In these cells, it has been identified that high-quality a-Si:H films deposited by a low-damage plasma process is key to achieving such high cell performance. However, the options for low-damage plasma deposition process are limited.
The main objectives of this work are to develop a low-plasma damage a-Si:H thin film deposition process based on remote plasma chemical vapor deposition (RPCVD) and to demonstrate high efficiency HJ solar cells on bulk substrates as well as on ultra-thin silicon and germanium substrates obtained by a novel, low-cost semiconductor-on-metal (SOM) technology.
This manuscript presents a detailed description of the RPCVD system and the process leading to the realization of high quality a-Si:H thin films and high efficiency HJ solar cells. First, p-type a-Si:H thin films are developed and optimized, then HJ solar cells are subsequently fabricated on bulk and ultra-thin Si and Ge SOM substrates without intrinsic a-Si:H passivation. Single HJ cells on ~ 500 µm bulk Si and ~25 µm ultra-thin substrates exhibited conversion efficiencies of η = 16% (Voc = 615 mV, Jsc = 34 mA/cm2, and FF = 77%) and η = 11.2% (Voc = 605 mV, Jsc = 29.6 mA/cm2, and FF = 62.8%), respectively. The performance of the ~25 µm cell was further improved to η = 13.4% (Voc = 645 mV, Jsc = 31.4 mA/cm2, and FF = 66.2%) by implementing the dual HJ architecture without front side i-layer passivation. For single HJ cells based on Ge substrates, the results were η = 1.78 % (Voc = 148 mV, Jsc = 35.1 mA/cm2, and FF = 1.78%) on ~500 µm bulk Ge, compared to η =5.3% (Voc = 203 mV, Jsc = 44.7 mA/cm2, and FF = 5.28%) on ~ 50 µm Ge SOM substrates. Respectively, the results obtained on ultra-thin SOM substrates are among the highest reported in literature for based on comparable architecture and substrate thickness.
In order to achieve improved cell performance, dual HJ cells with i-layer passivation of both surfaces were fabricated. First, optimized RPCVD-based i-layer films were developed by varying the deposition temperature and H2 dilution ratio (R). It was found that excellent surface passivation on planar substrates with as-deposited minority carrier lifetimes > 1 ms is achievable by using deposition temperature of 200 ºC and moderate dilution ratio 0.5 ≤ R ≤ 1, even without the more rigorous RCA pre-cleaning process typically used in literature for achieving comparable results. Subsequently, dual HJ solar cells with i-layer films were demonstrated on planar and textured bulk Si substrates showing improved conversion efficiencies of η = 17.3% (Voc = 664 mV, Jsc = 34.34 mA/cm2 and FF = 76%) and η = 19.4% (Voc = 643 mV, Jsc = 38.99 mA/cm2, and FF = 77.5%), respectively.text
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Chia-Ling, Li, and 李家羚. "Pattern formation and interaction of two-dimensional combustion waves and development of a large-scale and low-cost process for manufacturing silicon carbide." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/48867837396034177273.
Full textAbstract:
碩士國立中正大學
化學工程研究所
87
The thesis contains two parts. The first part is to study the pattern formation and interaction of two-dimensional combustion waves. In the system(Ti+C→TiC), we carried out three different combustion schemes, including ignition with a single heat source, ignition with two heat sources, and combustion with planted inhomogeneous mediums to observe what influence on pattern formation they made. In additions, for the arrangement with a single heat source, we also carried out combustion of large samples with different degree of dilutions. Furthermore, during the experiment process, we found a novel combustion phenomenon that one or a few hot spot traveled back and forth along the circular wavefront. It plays an important role in propagations and pattern formations of combustion waves. The second part is to develop a large-scale and low-cost process for manufacturing silicon carbide. From the literature, auxiliary treatments were required to produce SiC by the SHS method (self-propagating high- temperature synthesis), because of the low heat of formation of SiC. In a previous study, we found that direct combustion synthesis of SiC was possible, but the conversion length in the direction of the propagating combustion wave was very small. To overcome this drawback and develop a large-scale production process, large and thin reactant samples (120 ×120 ×6 mm), which were prepared from ground reactant powders and PVA solution, were prepared and combusted by a custom-built oxy-acetylene torch in air. The averaged yield was around 90%. In order to lower the production cost, larger Si particles were also used. The product phase and morphology were similar to those using smaller Si particles. A continuous production process based on this study is feasible.
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Fernandes, Bruno João Baptista. "pMOSFET fabrication using a low temperature pre-deposition technique." Master's thesis, 2016. http://hdl.handle.net/10362/20677.
Full textAbstract:
The objective of this work was to develop a fully functional pMOSFET using a new method for dopant pre-deposition done at low temperature (90ºC) using PECVD. This technique has many advantages when compared to the traditional manufacturing method, namely it is more cost effective, simpler and faster. Because it does not require an oxide layer to create the patterns, it can be conjugated with other low temperature techniques.
To obtain a functional pMOSFET, this work was divided in four different studies. The objective of the first study was to achieve metal-semiconductor ohmic contacts. To obtain a perfect ohmic contact of aluminum in a n-type silicon wafer, it is necessary to create a narrow space-charge region in order to allow carrier tunneling. That was reached by using a highly doped n-type hydrogenated amorphous silicon thin film made with a phosphine gas phase concentration of 1.5%, followed by a one-hour diffusion process at 1000ºC. A sheet resistance of 22.9 Ω/□ and a phosphorus surface concentration of 5.2 × 1019 aṫ cm-3 were obtained.
The second study consisted of producing p+n junctions varying the surface concentration and the diffusion time and temperature. The best diodes produced have significantly different profiles. The first was produced with a deep junction and a 0.165% diborane in the gas phase and presents the following parameters: rectification ratio of 6.01 × 103, threshold voltage of 0.53 V and an ideality factor of 1.74. The second diode was produced with a shallow junction and using a 1.5% diborane in the gas phase with the parameters: rectification ration of 3.94 × 103, a threshold voltage of 0.46 V and an ideality factor of 2.58.
Regarding the oxide characteristics for application as gate dielectric (third study), it was determined that the best oxides were produced by wet oxidation with a thickness of about 1300 Å.
After finishing the previous studies, it was possible to produce a fully functional p-type field effect transistor (fourth study). The MOSFETs worked in enhancement mode with the best parameters being: a threshold voltage of -4 V and a field effect mobility of 106.56 cm2/Vs.