Dissertations / Theses on the topic 'Multicrystalline'
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Gebregiorgis, Ashenafi Weldemariam. "Local Resistivity Measurement on Multicrystalline Silicon." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19278.
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Even though in the past the photovoltaic industry was dominated by single-crystalline silicon this days multi-crystalline silicon is consider to be on of the most promising material for application in low manufacturing cost solar photovoltaic arrays, consequently it has a huge potential to dominate the single-crystalline silicon in the photovoltaic industry in the next decades. However the presence of crystal defects such as dislocation and grain boundaries in multi-crystalline solar cells hugely reducing the conversion efficiency of this material compared to single crystalline silicon solar cell. Hence realizing the widespread utilization of this material will require understanding and control of the effects of this defects on the photovoltaic cell performance. Therefor we will examine the local resistivity of a given multi-crystalline sample in a dark and how it is affected by the presence of grain boundaries and the electrical activity when we cross or with in the grain boundary or twin boundaries. We have measured the resistivity of a number of samples of multi-crystalline silicon using a multi-height four-point probe.
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Schultz, Oliver. "High-efficiency multicrystalline silicon solar cells." München Verl. Dr. Hut, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=977880567.
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Li, Dai-Yin. "Texturization of multicrystalline silicon solar cells." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/64615.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 103-111).
A significant efficiency gain for crystalline silicon solar cells can be achieved by surface texturization. This research was directed at developing a low-cost, high-throughput and reliable texturing method that can create a honeycomb texture. Two distinct approaches for surface texturization were studied. The first approach was photo-defined etching. For this approach, the research focus was to take advantage of Vall6ra's technique published in 1999, which demonstrated a high-contrast surface texture on p-type silicon created by photo-suppressed etching. Further theoretical consideration, however, led to a conclusion that diffusion of bromine in the electrolyte impacts the resolution achievable with Vallera's technique. Also, diffusion of photocarriers may impose an additional limitation on the resolution. The second approach studied was based on soft lithography. For this approach, a texturization process sequence that created a honeycomb texture with 20 ptm spacing on polished wafers at low cost and high throughput was developed. Novel techniques were incorporated in the process sequence, including surface wettability patterning by microfluidic lithography and selective condensation based on Raoult's law. Microfluidic lithography was used to create a wettability pattern from a 100A oxide layer, and selective condensation based on Raoult's law was used to reliably increase the thickness of the glycerol/water liquid film entrained on hydrophilic oxide islands approximately from 0.2 pm to 2.5 pm . However, there remain several areas that require further development to make the process sequence truly successful, especially when applied to multicrystalline wafers.
by Dai-Yin Li.
Ph.D.
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Vecchi, Pierpaolo. "Defect analysis in directionally solidified multicrystalline silicon." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21177/.
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This project studies how the microstructure and metallic impurities affect the electrical properties of mc-Si wafers, to improve the efficiency and the production yield of photovoltaic solar cells.
Dislocations and impurities in silicon are recombination centres that reduce free carrier lifetime and thus efficiency of solar cells. The quality of the material can be improved by finding optimal growth conditions and a threshold value for the contamination that does not compromise the device efficiency.
Two sets of p-type mc-Si wafers located at different heights and lateral positions of two directionally solidified ingots, one contaminated with iron and one with aluminum, were analysed with several characterization techniques.
The two ingots show similar microstructure, but the top of the iron contaminated ingot has a significantly lower lifetime, as it contains more dislocation clusters decorated with segregated iron. Aluminum is less detrimental at this low concentration level and it is more homogeneously distributed along the ingot height.
A Mott-Schottky analysis after evaporation of aluminum contacts confirmed the p-type nature of the samples and estimated the free charge carrier concentration.
Current profiles and local I-V curves measured with Conductive Atomic Force Microscopy show that decorated grain boundaries are a preferential path for electrical conduction compared to the grain regions and iron precipitates affect more heavily the electrical properties of the wafer compared to aluminum precipitates.
The shape of the current profile at the boundary was justified with a theoretical model that assumes a redistribution of charge density due to a Coulombic potential introduced by a spherical and positively charged precipitate, that can be identified with b-FeSi2.
The results from this characterization show that metallic contamination at grain boundaries in Si is responsible for enhanced free carrier recombination and thus efficiency reduction in mc-Si cells.
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Macdonald, Daniel Harold, and daniel@faceng anu edu au. "Recombination and Trapping in Multicrystalline Silicon Solar Cells." The Australian National University. Faculty of Engineering and Information Technology, 2001. http://thesis.anu.edu.au./public/adt-ANU20011218.134830.
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In broad terms, this thesis is concerned with the measurement and interpretation of carrier lifetimes in multicrystalline silicon. An understanding of these lifetimes in turn leads to a clearer picture of the limiting mechanisms in solar cells made with this promising material, and points to possible paths for improvement. The work falls into three broad categories: gettering, trapping and recombination. A further section discusses a powerful new technique for characterising impurities in semiconductors in general, and provides an example of its application.
Gettering of recombination centres in multicrystalline silicon wafers improves the bulk lifetime, often considerably. Although not employed deliberately in most commercial cell processes, gettering nevertheless occurs to some extent during emitter formation, and so may have an important impact on cell performance. However, the response of different wafers to gettering is quite variable, and in some cases is non-existent. Work in this thesis shows that the response to gettering is best when the dislocation density is low and the density of mobile impurities is high. For Eurosolare material these conditions prevail at the bottom and to a lesser extent in the middle of an ingot. However, these conclusions can not always be applied to multicrystalline silicon produced by other manufacturers. Low resistivity multicrystalline silicon suffers from a concurrent thermally induced degradation of the lifetime. This had previously been attributed to the dissolution of precipitated metals, although we note that the crystallographic quality also appears to deteriorate. The thermal degradation effect results in an optimum gettering time for low resistivity material. Edge-defined Film-fed Growth (EFG) ribbon silicon was also found to respond to gettering, and even more so to bulk hydrogenation. Evidence for Cu contamination in the as-grown EFG wafers is presented.
Multicrystalline silicon is often plagued by trapping effects, which can make lifetime measurement in the injection-level range of interest very difficult, and sometimes impossible. An old model based on centres that trap and release minority carriers, but do not interact with majority carriers, was found to provide a good explanation for these effects. These trapping states were linked with the presence of dislocations and also with boron-impurity complexes. Their annealing behaviour and lack of impact on device parameters can be explained in terms of the models developed. The trapping model allowed a recently proposed method for correcting trap-affected data to be tested using typical values of the trapping parameters. The correction method was found to extend the range of useable data to approximately an order of magnitude lower in terms of carrier density than would be available otherwise, an improvement that could prove useful in many practical cases.
High efficiency PERL and PERC cells made on gettered multicrystalline silicon resulted in devices with open circuit voltages in the 640mV range that were almost entirely limited by bulk recombination. Furthermore, the injection-level dependence of the bulk lifetime resulted in decreased fill factors. Modelling showed that these effects are even more pronounced for cells dominated by interstitial iron recombination centres. Analysis of a commercial multicrystalline cell fabrication process revealed that recombination in the emitter created the most stringent limit on the open circuit voltage, followed by the bulk and the rear surface. The fill factors of these commercial cells were mostly affected by series resistance, although some reduction due to injection-level dependent lifetimes seems likely also. Secondary Ion Mass Spectroscopy on gettered layers of multicrystalline silicon revealed the presence of Cr and Fe in considerable quantities. Further evidence strongly implied that they resided almost exclusively as precipitates.
More generally, injection-level dependent lifetime measurements offer the prospect of powerful contamination-monitoring tools, provided that the impurities are well characterised in terms of their energy levels and capture cross-sections. Conversely, lifetime measurements can assist with this process of characterising impurities, since they are extremely sensitive to their presence. This possibility is explored in this thesis, and a new technique, dubbed Injection-level Dependent Lifetime Spectroscopy (IDLS) is developed. To test its potential, the method was applied to the well-known case of FeB pairs in boron-doped silicon. The results indicate that the technique can offer much greater accuracy than more conventional DLTS methods, and may find applications in microelectronics as well as photovoltaics.
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Orellana, Pérez Teresa. "Mechanical behavior of alternative multicrystalline silicon for solar cells." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-117455.
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The usage of more inexpensive silicon feedstock for the crystallization of multicrystalline silicon blocks promises cost reduction for the photovoltaic industry. Less expensive substrates made out of metallurgical silicon (MG-Si) are used as a mechanical support for the epitaxial solar cell. Moreover, conventional inert solar cells can be produced from up-graded metallurgical silicon (UMG-Si). This feedstock has higher content of impurities which influences cell performance and mechanical strength of the wafers. Thus, it is of importance to know these effects in order to know which impurities should be preferentially removed or prevented during the crystallization process. Solar cell processing steps can also exert a change in the values of mechanical strength of processed multicrystalline silicon wafers until the fabrication of a solar cell.
Bending tests, fracture toughness and dynamic elastic modulus measurements are performed in this work in order to research the mechanical behavior of multicrystalline silicon crystallized with different qualities of silicon feedstock. Bending tests and residual stress measurements allows the quantification of the mechanical strength of the wafers after every solar cell processing step. The experimental results are compared with theoretical models found in the classical literature about the mechanical properties of ceramics. The influence of second phase particles and thermal processes on the mechanical strength of silicon wafers can be predicted and analyzed with the theoretical models.
Metals like Al and Cu can decrease the mechanical strength due to micro-cracking of the silicon matrix and introduction of high values of thermal residual stress. Additionally, amorphous silicon oxide particles (SiOx) lower the mechanical strength of multicrystalline silicon due to thermal residual stresses and elastic mismatch with silicon. Silicon nitride particles (Si3N4) reduce fracture toughness and cause failure by radial cracking in its surroundings due to its thermal mismatch with silicon. Finally, silicon carbide (SiC) and crystalline silicon oxide (SiOx) introduce thermal residual stresses but can have a toughening effect on the silicon matrix and hence, increase the mechanical strength of silicon wafers if the particles are smaller than a certain size.
The surface of as-cut wafers after multi-wire sawing presents sharp micro-cracks that control their mechanical behavior. Subsequent removal of these micro-cracks by texture or damage etching approximately doubles the mechanical strength of silicon wafers. The mechanical behavior of the wafers is then governed by defects like cracks and particles formed during the crystallization of multicrystalline silicon blocks. Further thermal processing steps have a minor impact on the mechanical strength of the wafers compared to as-cut wafers. Finally, the mechanical strength of final solar cells is comparable to the mechanical strength of as-cut wafers due to the high residual thermal stress introduced after the formation of the metallic contacts which makes silicon prone to crack.
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Al-Amin, Mohammad. "Low-temperature gettering in multicrystalline silicon materials for photovoltaics." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/95505/.
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This thesis presents results on the effects of low-temperature gettering processes on minority carrier lifetime in multicrystalline silicon. Wafers are sourced from different height positions of a commercially-grown ingot. The distribution of different key material properties including bulk lifetime, interstitial iron concentration, and dislocation density are characterised and are found to vary widely with ingot height position. Lifetimes are measured by using temporary liquid iodine-ethanol passivation at room temperature or silicon nitride films deposited by plasma-enhanced chemical vapour deposition. Lifetimes are lower in samples from the extrema of ingot than the centre parts. Interstitial iron concentrations are found to be highest in the bottom samples and lowest at the centre of the ingot. Dislocation density is lowest at the bottom of the ingot and increases with ingot height position. In as-grown wafers, low-temperature gettering can improve lifetime substantially in relatively poor samples from the extrema of the ingot. Iodine-ethanol passivation is used to separate thermal effects of annealing from any bulk passivation which may occur during surface passivation from lifetime measurement. The largest relative lifetime improvement (from 5.5 μs to 38.7 μs) is achieved in material from the bottom of the ingot with annealing at 400°C for 35 h. The benefit of low-temperature annealing is marginal for middle samples. Bulk interstitial iron concentrations decrease by up to 2.1 order of magnitude in the bottom samples. The reduction in interstitial iron concentration is not found to be systematically dependent on annealing temperature. For bottom samples a good correlation between the changes in lifetime and interstitial iron concentration is found. The effects of different passivation schemes on low-temperature gettering is also investigated. The results show that starting lifetime and interstitial iron concentration strongly depends on the choice of passivation scheme. The effect of different surface passivation schemes is more pronounced in relatively high lifetime samples. In samples from the bottom of the middle of the wafer, lifetime improves from 113 μs to 171 μs with silicon nitride passivation upon annealing at 400 °C for 25 h. Supporting results from secondary ion mass spectrometry show that substantial concentrations of iron exist in the silicon nitride film after low-temperature annealing. This suggests silicon nitride layer might be an additional gettering centre for interstitial iron. This thesis also studies the effects of low-temperature annealing combined with a standard phosphorus diffusion process to form an emitter. Lifetime in samples from the top and bottom of the ingot can be improved by annealing at 300°C and 400°C even after the phosphorus diffusion process. The largest improvement is from 54 μs to 78 μs upon post-diffusion annealing of bottom samples at 300°C, and the results suggest gettering of impurities other than interstitial iron is likely. The phosphorus diffused emitter layers do not act as effective additional gettering sites for interstitial iron upon low-temperature annealing. The lifetime improvement upon pre-diffusion annealing is retained after the diffusion process. In summary, low-temperature annealing has the potential to improve the lifetime in as-grown multicrystalline silicon and after a phosphorus diffusion gettering under some conditions. Low-temperature annealing thus provides a potential low cost route to improve multicrystalline solar cell efficiencies.
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Vogl, Michelle (Michelle Lynn). "Dislocation density reduction in multicrystalline silicon through cyclic annealing." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68956.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 77-78).
Multicrystalline silicon solar cells are an important renewable energy technology that have the potential to provide the world with much of its energy. While they are relatively inexpensive, their efficiency is limited by material defects, and in particular by dislocations. Reducing dislocation densities in multicrystalline silicon solar cells could greatly increase their efficiency while only marginally increasing their manufacturing cost, making solar energy much more affordable. Previous studies have shown that applying stress during high temperature annealing can reduce dislocation densities in multicrystalline silicon. One way to apply stress to blocks of silicon is through cyclic annealing. In this work, small blocks of multicrystalline silicon were subjected to thermal cycling at high temperatures. The stress levels induced by the thermal cycling were modeled using finite element analysis (FEA) on Abaqus CAE and compared to the dislocation density reductions observed in the lab. As too low of stress will have no effect on dislocation density reduction and too high of stress will cause dislocations to multiply, it is important to find the proper intermediate stress level for dislocation density reduction. By comparing the dislocation density reductions observed in the lab to the stress levels predicted by the FEA modeling, this intermediate stress level is determined.
by Michelle Vogl.
S.M.
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Schultz, Oliver [Verfasser]. "High-efficiency multicrystalline silicon solar cells / vorgelegt von Oliver Schultz." München : Verl. Dr. Hut, 2005. http://d-nb.info/977880567/34.
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Austad, Karianne. "Characterization of electrical activity and lifetime in compensated multicrystalline silicon." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13263.
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This master's thesis concerns the electrical activity and lifetime in compensated multicrystalline silicon wafers used for solar cell production.Resistivity profiles across grain boundaries have been obtained by a Four Point Probe (FPP). Profiles have been investigated in relation to minority carrier lifetime acquired by Microwave Photo Conductance Decay (uW-PCD).It has been found that a two-step process consisting of pre-annealing at either 600C or at 900C followed by phosphorus diffusion (P) gettering will increase the electrical activity of crystalline defects. It has been proposed that a P gettering step should follow directly after annealing for a better dissolution of metallic precipitates. Introduced defects in the material as a consequence of both pre-annealing at 900$^circ$C and of resistivity measurements before gettering, have possibly enhanced the phosphorus diffusion depth in the gettering process. The higher concentration of phosphorus has lead to an augmented lifetime in the material. Metallic impurity precipitation at defects, affecting the electrical activity and the minority carrier recombination rate, has been observed. A good correlation between grain structure, resistivity- and lifetime profiles has thus been established.
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Henriksen, Lisa Grav. "Pump-probe experiments of multicrystalline silicon for solar cell applications." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19207.
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In order to make cost effective solar cells from mc-Si materials, the negative contributions from defects and impurities should be reduced. The analysis of the photogenerated carrier properties is therefore of great importance for characterising carrier processes and hence, for improving the material performance.In this work, pump-probe measurement of a range of silicon wafers have been performed, using anultrafast laser of 800 nm wavelength and 85 fs pulses. The optical response in the samples were analysed by measuring the reflected probe beam initial transient.The purpose of this theses was to explore the use of pump-probe experiment to study carrier dynamics in mc-Si. Measurements of single c-Si samples were used as a basis for developing good experimental skills as well as achieving knowledge about carrier dynamics in c-Si. The initial Delta R/R was studied for a range of input parameters, aiming to characterise important contributions to the measurements.The effects of passivation has been studied, indicating a significant contribution to R~R. Etchingoff the passivated layer of an oxide (SiO2) wafer, showed a radically increased in pump beam reflectivity, from 9% to 32%, and a reduced DeltaR~R from 47×10-6 to 37×10-6 was be observed. Analysis has showed that incident angle may be chose such that the pump reflection loss is at a minimum for the given passivation thickness.The final results showed a R~R is in the range of (14-41)e-6 for bare c-Si, and (47-171)e-6 for passivated c-Si wafers.Ultrafast initial recovery has been observed for mc-Si samples, and attributed to trapping of carriers. Decay times in the range of 1-6 ps are deduced and trapping densities are found as (1:3 - 4:3) × 10^18 cm-3, which is in the same order as the excitation densities.A methodology for using pump-probe measurements to analyse mc-Si samples is established, and the technique is used in characterising the observed defect states, which is of great interest for improving solar cell materials.
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Lilliestråle, Johan Carl Åke. "Structural properties of Ge doped multicrystalline Silicon wafers and Solar cells." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18886.
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The efficiency of multi crystalline silicon solar cells is around 17% but the theoretical limit is 33,7 %. Impurities and dislocations are the main sources for degradation of the solar cell efficiency, especially the combination. Dislocations are also responsible for plastic deformation of materials. To improve the solar cell efficiency it is important to reduce the dislocation density in the raw material for solar cells. The nucleation and multiplication of dislocations in wafer can be suppressed by doping it with a method called solid solute strengthening. In solar cells, the minority carrier lifetime, internal quantum efficiency and the solar cell efficiency are also affected by germanium despite although it is, electrically inactive in the silicon lattice. In this thesis I have studied how all these factors are affected by germanium with different experimental methods. The main goal is to conclude if germanium could be a cost effective dopant in future solar cell production.
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Sana, Peyman. "Design, fabrication and analysis of high efficiency multicrystalline silicon solar cells." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15039.
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Karzel, Philipp [Verfasser]. "Reduction and Analysis of Lifetime-limiting Defects in Multicrystalline Silicon / Philipp Karzel." München : Verlag Dr. Hut, 2014. http://d-nb.info/1051550114/34.
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Dadzis, Kaspars. "Modeling of directional solidification of multicrystalline silicon in a traveling magnetic field." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-117492.
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Melt flow plays an important role in directional solidification of multicrystalline silicon influencing the temperature field and the crystallization interface as well as the transport of impurities. This work investigates the potential of a traveling magnetic field (TMF) for an active control of the melt flow. A system of 3D numerical models was developed and adapted based on open-source software for calculations of Lorentz force, melt flow, and related phenomena. Isothermal and non-isothermal model experiments with a square GaInSn melt were used to validate the numerical models by direct velocity measurements. Several new 3D flow structures of turbulent TMF flows were observed for different melt heights. Further numerical parameter studies carried out for silicon melts showed that already a weak TMF-induced Lorentz force can stir impurities near to the complete mixing limit. Simultaneously, the deformed temperature field leads to an increase of the deflection of crystallization interface, which may exhibit a distinct asymmetry. The numerical results of this work were implemented in a research-scale silicon crystallization furnace. Scaling laws for various phenomena were derived allowing a limited transfer of the results to the industrial scale.
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Jensen, Mallory Ann. "Root cause defect identification in multicrystalline silicon for improved photovoltaic module reliability." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119344.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 135-145).
To meet climate targets by 2030, manufacturing capacity for photovoltaic (PV) modules must be scaled at 22-25% annual growth rate while maintaining high performance and low selling price. The most suitable material substrate to enable this scale-up is cast multicrystalline silicon (mc-Si) due to its low operating cost and capital requirements compared to other technologies. However, a new form of light-induced degradation was discovered when transitioning mc-Si to the latest high efficiency device architecture. Light- and elevated temperature-induced degradation (LeTID) causes performance to decrease by about 10% (relative) under field-relevant conditions within only four months. In this work, the root cause of LeTID is investigated in three parts: (1) Candidate hypotheses are developed for LeTID; (2) Targeted experiments are carried out toward developing a defect-based description of LeTID; and (3) The basis for a predictive model of LeTID is proposed. Techniques including minority carrier lifetime spectroscopy, synchrotron-based X-ray fluorescence, intentional contamination, and process simulation are employed to probe the defect causing LeTID. The results indicate that LeTID is caused by at least two reactants-hydrogen and one or more reactants that can be modified by high-temperature processing-and that the defect at the point of maximum degradation has recombination characteristics similar to a deep-level donor in silicon. By providing the basis for a predictive model, this work enables both identification of the root cause of LeTID and de-risking of novel solar cell architectures based on mc-Si, allowing assessment of the impact of LeTID on the future of the PV industry. This work also enables development of mitigating strategies for LeTID.
Funding from the National Science Foundation Graduate Research Fellowship Program and grants from the National Science Foundation and the U.S. Department of Energy
by Mallory Ann Jensen.
Ph. D.
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Skenes, Kevin. "Characterization of residual stresses in birefringent materials applied to multicrystalline silicon wafers." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53050.
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Birefringence has been used to study transparent materials since 1815, and is based on the decomposition of a polarized ray of light into two distinct rays when passing through an optically anisotropic material. This thesis uses this phenomenon in a study of phase retardation in crystalline materials. Single and multicrystalline silicon was chosen as the model material. Silicon is an interesting and important material in its own right, and the use of photoelasticity to determine stresses at linear and planar defects can have important consequences in the electrical performance of devices such as electronics and photovoltaic cells. This thesis presents the results of an experimental investigation of residual stresses in multicrystalline silicon wafers using near-infrared (NIR) transmission photoelasticity. NIR transmission through multicrystalline silicon is found to vary with crystallographic orientation and relate to planar atomic density, enabling the assignment of appropriate stress-optic coefficients to different grains. Noise in the data is reduced with the Ramji and Ramesh 10-step phase shifting algorithm when compared to the Patterson and Wang process. Normal stresses at points of zero maximum shear stress can be characterized based on isoclinic behavior around the point. Points at which all normal stresses are zero serve as boundary conditions for shear difference integration and allow for stress separation from a point that is not a free boundary. The second part of this work focuses on residual stresses in silicon wafers subjected to known physical damage such as indentations. Residual stress fields around Vickers indentations in silicon are found to be larger in size than predicted by contact mechanics. Placing Vickers indentations in close proximity creates a secondary stress field surrounding the entire indentation array, and a relationship is developed to explain this behavior. High residual stresses measured at grain boundaries are found to be consistent with models of atomic displacement. Placement of Vickers indentations near grain boundaries results in a change in stress state at the grain boundaries. The results of this study demonstrate the capacity of birefringence as a non-destructive evaluation tool and describe the effects of residual stress concentrations in silicon wafers.
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Brody, Jed. "Doping dependence of surface and bulk passivation of multicrystalline silicon solar cells." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180041/unrestricted/brody%5Fjed%5F200312%5Fphd.pdf.
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Nakayashiki, Kenta. "Understanding of defect passivation and its effect on multicrystalline silicon solar cell performance." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19854.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dr. Ajeet Rohatgi; Committee Member: Dr. Bernard Kippelen; Committee Member: Dr. Gabriel Rincon-Mora; Committee Member: Dr. Miroslav Begovic; Committee Member: Dr. W. Brent Carter.
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Scott, Stephanie Morgan. "Sacrificial high-temperature phosphorus diffusion gettering for lifetime improvement of multicrystalline silicon wafers." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92128.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 71-75).
Iron is among the most deleterious lifetime-limiting impurities in crystalline silicon solar cells. In as-grown material, iron is present in precipitates and in point defects. To achieve conversion efficiencies in excess of 20%, bulk minority-carrier lifetimes in excess of 300 Rs (p-type) are required [1]. For cost-effective multicrystalline silicon wafers, achieving this lifetime often requires gettering. Gettering at higher temperatures for longer times is often necessary to fully dissolve and remove precipitated impurities. However, such time temperature profiles can result in unacceptably deep emitters, affecting the blue response of the finished device. Here, we explore a "sacrificial" gettering step, in which gettering and emitter-formation steps are decoupled and optimized independently. The optimization of the sacrificial gettering step is guided by the Impurity-to-Efficiency simulation tool [2] and explores higher temperatures (up to 1100°C) than standard industrial processes (typically 820-850°C). The models indicate that iron concentration should be reduced by higher-temperature gettering, which is confirmed by experiment. However, uniform lifetime degradation occurs at higher temperatures, suggesting another homogeneously distributed defect is generated as a result of the high-temperature gettering process. A list of candidate defects is presented.
by Stephanie Morgan Scott.
S.M.
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Ryningen, Birgit. "Formation and growth of crystal defects in directionally solidified multicrystalline silicon for solar cells." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-4980.
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Chiguluri, Praneeth. "Quasi-steady-state Photoluminescence Lifetime Imaging of p- and n-type Multicrystalline Silicon Wafers." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1300311806.
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Stoffers, Andreas Verfasser], Dierk [Akademischer Betreuer] Raabe, and Joachim [Akademischer Betreuer] [Mayer. "Grain boundary segregation in multicrystalline silicon studied by correlative microscopy / Andreas Stoffers ; Dierk Raabe, Joachim Mayer." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1161739521/34.
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Stoffers, Andreas [Verfasser], Dierk Akademischer Betreuer] Raabe, and Joachim [Akademischer Betreuer] [Mayer. "Grain boundary segregation in multicrystalline silicon studied by correlative microscopy / Andreas Stoffers ; Dierk Raabe, Joachim Mayer." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1161739521/34.
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Bredemeier, Dennis [Verfasser]. "Light and elevated Temperature Induced Degradation (LeTID) of the carrier lifetime in multicrystalline silicon / Dennis Bredemeier." Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2020. http://d-nb.info/1211083705/34.
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Bolisetty, Sreenivasulu. "Novel Process and Manufactur of Multi crystalline Solar Cell." Thesis, Linköping University, Department of Science and Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-17580.
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Patterning of multi crystalline silicon Solar cell is prepared with photolithography etching. Electroless plating is used to get metallization of Nickel contacts. SEM analysis of Nickel deposition and measurement of contact resistance for series and shunt resistance is done. To increase the fill factor, the screen printed electrodes are subjected to different firing temperatures there by increasing the efficiency of solar cell. Nickel-silicide formation at the interface between the Silicon and Nickel enhances stability and reduces the contact resistance, resulting in higher energy conversion efficiency.
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Cai, Li. "Improved understanding and control of the properties of PECVD silicon nitride and its applications in multicrystalline silicon solar cells." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/15468.
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Fleck, Martin Gabriel [Verfasser]. "The Influence of High Temperature Steps on Defect Etching and Dislocations : Etch Pit Density Reduction in Multicrystalline Silicon / Martin Gabriel Fleck." Konstanz : KOPS Universität Konstanz, 2020. http://d-nb.info/1233203193/34.
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Dadzis, Kaspars [Verfasser], H. J. [Akademischer Betreuer] Möller, and André [Gutachter] Thess. "Modeling of directional solidification of multicrystalline silicon in a traveling magnetic field / Kaspars Dadzis ; Gutachter: André Thess ; Betreuer: H. J. Möller." Freiberg : Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://d-nb.info/1220837288/34.
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Castellanos, Rodríguez Sergio. "Application of infrared birefringence imaging for measuring residual stress in multicrystalline, quasi-mono, dendritic web, and string ribbon silicon for solar cells." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/88385.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 96-102).
One of the parameters with highest impact on photovoltaic module cost is manufacturing yield during solar cell production. Yield is, to a great extent, directly affected by the crystallization technique used to grow the substrate wafers due to its role in generating residual stresses that can lead to fracture upon wafer processing and handling. This thesis explores the nature, impact, and a method for quantifying residual stresses in silicon wafers used for solar cells. The combination of an infrared birefringence imaging technique along with a sectioning method is proposed as an approach to spatially resolve and decouple the in-plane residual stress components on four wafers originating from different growth methods. The suitability of this technique is verified, and recommendations for future expansion of this work are presented.
by Sergio Castellanos Rodriguez.
S.M.
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Micard, Gabriel [Verfasser]. "Quantitative Investigation of Grain Boundary Recombination Activity in multicrystalline Silicon using Light Beam Induced Current Contrast Profiles : Analytical Models and Applications / Gabriel Micard." Konstanz : Bibliothek der Universität Konstanz, 2011. http://d-nb.info/101793388X/34.
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Orellana, Pérez Teresa [Verfasser], Hans Joachim [Akademischer Betreuer] Möller, Hans Joachim [Gutachter] Möller, and Cano Jose Ygnacio [Gutachter] Pastor. "Mechanical behavior of alternative multicrystalline silicon for solar cells / Teresa Orellana Pérez ; Gutachter: Hans Joachim Möller, Jose Ygnacio Pastor Cano ; Betreuer: Hans Joachim Möller." Freiberg : Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://d-nb.info/122083727X/34.
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Oliver, Cyril. "Dopage au Bore du Silicium Multicristallin de type N : application à la fabrication de cellules photovoltaïques par un procédé industriel." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20199/document.
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Cette thèse présente le développement d'un équipement permettant le dopage Bore des cellules photovoltaïques à base de silicium de type n. Un four de diffusion, appartenant à la société Semco Engineering a été développé pour tirer profit du procédé LYDOP (Leaktight Yield Doping en anglais), breveté par la société. Ce dernier a permis la mise au point d'un procédé de diffusion du Bore, régulé sous basse pression, intégrant une source dopante gazeuse à base de BCl3 afin d'effectuer le dopage de plusieurs plaques de silicium simultanément. Les principaux paramètres influençant le procédé de dopage ont été étudiés pour obtenir un dopage très uniforme sur plaque et sur nacelle. Une large gamme de résistances carrées d'émetteurs (de 40 à 100 ohm/sq) a été obtenue avec une uniformité inférieure à 5% sur plaque et sur nacelle. Le développement du procédé de dopage a conduit à étudier deux méthodes de fabrication d'une cellule photovoltaïque sur silicium multicristallin de type n. Plusieurs méthodes pour la formation de l'émetteur Bore sur une seule face ont été présentées : masquage (SiNx, SiO2), dopage back-to-back ou gravure chimique. De cette étude, deux procédés de fabrication (flowcharts) ont été développés pour la fabrication de cellules photovoltaïques : la première par gravure à l'hydroxyde de potassium (KOH) de l'émetteur, la seconde en effectuant le dopage bore des cellules en position back-to-back (dos à dos). Un rendement sur cellule de 13,2% et 14,4% a été obtenu respectivement pour chacune des flowcharts. Ces résultats, limités principalement par les étapes de passivation et de métallisation permettent de démontrer l'utilisation du procédé Bore comme solution à la formation des émetteurs p+This thesis presents the development of an equipment for boron doping of n-type multicrystalline silicon solar cells. A diffusion furnace was developed by Semco Engineering Company. It was built using LYDOP (LeakTight Yields DOPing) technology, patented by Semco. This one permits a simultaneous doping of a big amount of silicon wafers using regulated low pressure processes. Boron diffusion process development was carried out using LYDOP's specifications with BCl3 as gaseous doping source. Main parameters have been studied to control diffusion process. Several sheet resistance values of emitters were achieved (from 40 to 100 ohm/sq) with uniformity under 5% within wafer and within boat by tuning process parameters. Doping process development leads us to investigate how to create a single side emitter with n-type multicrystalline solar cells. Two fabrications flowcharts were presented: one using KOH emitter etches on backside and the other using back-to-back positioning during boron diffusion. Comparison between both flowcharts carried out to 13,2% and 14,4% efficiencies solar cells, respectively on each flowchart. Results are limited by passivation and metallization of emitters. However boron diffusion process demonstrate that LYDOP technology is well adapted to develop n-type solar cells
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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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Zierer, Robert. "Wechselwirkungen von interstitiellem Eisen mit Defekten im multikristallinen Silizium." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-156584.
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Innerhalb dieser Arbeit werden die Wechselwirkungen von interstitiellem Eisen mit Defekten, wie Versetzungen und Ausscheidungen, untersucht. Dazu wurde zunächst das Löslichkeitsverhalten von Eisen im p-dotierten mc-Silizium im Temperaturbereich von 550°C bis 800°C gemessen. An Versetzungsstrukturen konnte in einigen Bereichen eine deutlich erhöhte Konzentration an gelöstem Eisen im as cut Zustand und nach dem Tempern der Probe festgestellt werden. Diese wurde mit der Struktur der Versetzungsanordnung erklärt. An vorhandenen Ausscheidungen im Silizium konnte eine Abnahme der gelösten Eisenkonzentration beobachtet werden. Die Dichte und Morphologie der Ausscheidungen haben dabei einen großen Einfluss. Der Eintrag des Eisens in das Silizium aus Tiegeln mit unterschiedlicher Reinheit während der Kristallisation wurde untersucht. Dabei zeigte sich ein deutlicher Einfluss der Tiegelreinheit auf die Konzentration am Rand des Blockes, jedoch nur einen geringen Einfluss auf die Eisenkonzentration im Blockinneren.
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Schmid, Ekaterina. "Einfluss der Züchtungsbedingungen auf die Eigenschaften von mc-Si-Kristallen." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-199263.
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Die vorliegende Arbeit befasst sich mit den Untersuchungen zum Einfluss der Züchtungsbedingungen auf die Eigenschaften von multikristallinen (mc) Silizium-Kristallen. Im Mittelpunkt stehen Züchtungsexperimente mit einer gezielten Variation der Züchtungsaufbauten und Züchtungsgeschwindigkeiten. Die gezüchteten Kristalle wurden umfassend charakterisiert im Hinblick auf die Kohlenstoffkonzentration, die Kornstruktur, die Vesetzungsdichte, Verteilung der Ausscheidungen und Ladungsträgerlebensdauer. Zusätzlich wurde die Versetzungsanordnung in Abhängigkeit von der Wachstumsrate bzw. Abkühlrate systematisch untersucht. Als Ergebnis wurde gezeigt, dass die Züchtungsbedingungen die Kohlenstoffkonzentration, die Versetzungsdichte, die Bildung von den Ausscheidungen sowie die Ladungsträgerlebensdauer beeinflussen können, jedoch nicht die Korngröße. Es wurde ein direkter Zusammenhang zwischen Ausscheidungsgebieten und erhöhte Versetzungsdichte beobachtet. Im Rahmen der Arbeit wurde festgestellt, dass die endgültige Versetzungsstruktur sich als Resultat von Gleit- und Erholungsprozessen darstellt.
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Kreßner-Kiel, Denise. "Wechselwirkung von Kupfer mit ausgedehnten Defekten in multikristallinem Silicium und Einfluss auf die Rekombinationseigenschaften." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-229212.
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Die Rekombinationsaktivität von Versetzungen und Korngrenzen in multikristallinem Silicium wird von Kupfer und anderen metallischen Verunreinigungen wie Eisen mitbestimmt. Das Hauptziel der Arbeit war es, die Verteilung von Kupfer und dessen Wirkung auf die Rekombinationsaktivität von Versetzungen und Korngrenzen genauer zu untersuchen. Dazu wurden optische und elektrische Untersuchungen an gezielt mit Metallen verunreinigten Modellmaterialien durchgeführt. Nicht alle Versetzungen sind rekombinationsaktiv. Es konnte gezeigt werden, dass der Anteil rekombinationsaktiver Versetzungen am Gesamtinventar und die Hintergrunddiffusionslänge von der Verunreinigung mit Metallen abhängig sind. Ergebnisse von Untersuchungen an Proben, die Diffusionsexperimenten unterzogen wurden, deuten auf unterschiedliches Ausscheidungsverhalten von Kupfer und Eisen hin sowie auf Wechselwirkungen mit Versetzungen und Korngrenzen, die mit der Diffusionstemperatur und den Abkühlbedingungen in Zusammenhang stehen.
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Nilsson, Amanda, and Nora Orrenius. "How to reduce the total environmental, economic and social impact of Solar Cell Panels." Thesis, KTH, Industriell ekonomi och organisation (Inst.), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298239.
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To be able to mitigate the climate change and disasters that will come with it and to ensure economic growth, there is a need for change. A good start is more renewable energy and less harmful emissions. It is known that solar energy is sustainable and made from an endless source, the sun. However, it is not known how much impact the photovoltaic solar panels have through its entire lifecycle, from extraction of raw materials to End of Life management. This study has investigated photovoltaic solar panels' full life cycle to see how sustainable they really are. Including where the biggest opportunities for improvement of environmental, financial and social sustainability within the value chain is found. The results have been obtained by conducting a literature study, interviews with people with expertise of different parts of the value chain and finally calculations have been made to compare and visualize the findings. Two main ways to improve the PV panels’ negative impact in terms of environmental, financial and social sustainability have been established. Firstly, the study suggests the importance of implementing advanced recycling within the value chain. Recycling a high percentage of materials in the PV panel, and reusing the recovered material in production will decrease the energy consumption and harmful emissions significantly, alongside increasing circularity of critical materials and bring both financial and social benefits. Secondly, moving the better part of the production to Europe from China would also decrease the negative impact of the PV panels, especially the environmental and social impact, the study could however not find sufficiently good arguments for financial improvement to move the production to Europe. To be conclusive, this subject would need further studies.För att kunna lindra klimatförändringar och de medföljande katastroferna och säkerställa den ekonomiska tillväxten finns det ett stort behov av förändring. En bra start är att använda mer förnybar energi och som bidrar till färre skadliga utsläpp. Det är känt att solenergi är hållbart med bränsle från en oändlig källa, solen. Det är emellertid inte känt hur stor påverkan solcellspanelerna har under hela dess livscykel, från utvinning av råvaror till dess panelens liv är över. Denna studie har undersökt solcellspanelernas hela livscykel för att se hur hållbara de egentligen är. Studien har även studerat var de största möjligheterna för förbättring av miljömässig, finansiell och social hållbarhet inom värdekedjan finns. Resultaten har erhållits genom att genomföra en litteraturstudie, intervjuer av personer med expertis inom olika delar av värdekedjan och slutligen har beräkningar gjorts för att jämföra och visualisera resultaten. Två huvudsakliga sätt att förbättra solpanelernas negativa påverkan när det gäller miljömässig, ekonomisk och social hållbarhet har identifierats. För det första föreslår studien vikten av att implementera avancerad återvinning inom värdekedjan. Återvinning av en hög andel material i solcellspanelen och återanvändning av det återvunna materialet i produktionen kommer att minska energiförbrukningen och skadliga utsläpp avsevärt samt förbättra cirkuläriteten av kritiska material och medföra både ekonomiska och sociala fördelar. För det andra skulle förflyttning av den större delen av produktionen till Europa från Kina också minska de negativa effekterna av solcellspaneler, särskilt de miljömässiga och sociala effekterna, studien kunde dock inte hitta tillräckligt med goda argument för att en förflyttning av produktionen till Europa skulle leda till en ekonomisk förbättring. För att detta ska vara avgörande skulle detta ämne behöva ytterligare studier.
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Ghosh, Michael. "Defekte im Bodenbereich blockerstarrten Solar-Siliziums." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2010. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-38493.
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Etwa die Hälfte aller Solarzellen weltweit wird aus blockerstarrtem Silizium hergestellt. Derartige Blöcke weisen in ihren Außenbereichen eine verringerte Diffusionslänge der Minoritätsladungsträger auf. Um die Ursache dafür im Fall des bodennahen Bereichs zu bestimmen wurden zwei Spezialblöcke (ein Block mit reduzierter Bor-Dotierung und ein Block mit Phosphor-Dotierung) - u. a. mittels DLTS und FTIR - auf Kristalldefekte untersucht. Zusätzlich zu Dotierelementen (B, P, Al, As) wurden im Bodenbereich folgende Defekte nachgewiesen:
Metalle: Fe, Cr
Sauerstoffhaltige Defekte: Interstitieller Sauerstoff, Thermische Donatoren (TD), O1, O2
Stickstoffhaltige Defekte: NN-Paar, NNO-Komplex, Shallow Thermal Donors (STD)
Ausgedehnte Defekte: Versetzungen, Ausscheidungen, Korngrenzen.
Die Verteilung der flachen Donatoren (P, TD, STD, As) und Akzeptoren (B, Al) bestimmt den Widerstandsverlauf im bodennahen Bereich des Phosphor dotierten Spezialblocks. Das dortige Diffusionslängenprofil kann im Rahmen der Shockley-Read-Hall-Statistik erst durch eine Erhöhung des Minoritätseinfangquerschnitts für das Cr-Niveau (Faktor 5) bzw. für das STD-Niveau (Faktor 10) nachgezeichnet werden. Eisen, Versetzungen und Korngrenzen haben hier keinen wesentlichen Einfluss. In den untersten Millimetern des Spezialblocks müssen weitere Defekte hinzukommen, die die Diffusionslänge zusätzlich reduzieren; Thermische Donatoren und O1 und eventuell Ausscheidungen kommen dazu in Frage.
Die sinngemäße Übertragung der Konzentrationsverläufe aus den beiden Spezialblöcken auf einen Block mit einer produktionsüblichen Dotierung ([B]≈1016/cm3) ergibt, dass in diesem Fall verschiedene Defekte (TD, STD, CrB und FeB) einen Beitrag zur Diffusionslängenreduktion im bodennahen Blockbereich liefern.
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Favre, Wilfried. "Silicium de type n pour cellules à hétérojonctions : caractérisations et modélisations." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00635222.
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Les cellules à hétérojonctions de silicium fabriquées par croissance de couches minces de silicium amorphe hydrogéné (a-Si :H) à basse température sur des substrats de silicium cristallin (c-Si) peuvent atteindre des rendements de conversion photovoltaïque élevés (η=23 % démontré). Les efforts de recherche ayant principalement été orientés vers le cristallin de type p jusqu'à présent en France, ce travail s'attache à l'étude du type n pour d'une part déterminer les performances auxquelles s'attendre avec cette nouvelle filière et d'autre part les améliorer. Pour cela, nous avons mis en œuvre des techniques de caractérisation des matériaux composant la structure et de l'interface (a-Si :H/c-Si) couplées à des outils de simulations numériques afin mieux comprendre les phénomènes de transport électronique. Nous nous sommes également intéressés aux cellules à hétérojonctions avec substrats de silicium multicristallin de type n, le silicium multicristallin étant le matériau le plus répandu actuellement dans la fabrication des cellules photovoltaïques.
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Stocks, Matthew. "High efficiency multicrystalline silicon solar cells." Phd thesis, 1998. http://hdl.handle.net/1885/144956.
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Serra, Filipe. "Multicrystalline Silicon Ribbons Grown Over a Dust Substrate." Doctoral thesis, 2020. http://hdl.handle.net/10451/49758.
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O Silício sobre Substrato de Pó (SDS da sigla em inglês) é um processo desenvolvido para fabricar fitas de silício multicristalino directamente a partir de uma fonte gasosa (silano), evitando as etapas industriais de deposição de poli-silício, crescimento de cristal e corte em bolachas. Este processo tem por objectivo alcançar um material com boa qualidade cristalográfica para o fabrico de células solares, aliado a uma expressiva redução do custo global dos sistemas fotovoltaicos.
O foco do trabalho apresentado nesta tese é o aperfeiçoamento de toda a técnica SDS, a qual consiste em três passos principais: (i) produção de pó de silício; (ii) deposição química em fase de vapor (CVD da sigla em inglês) de silício sobre um substrato de pó de silício; e (iii) recristalização por zona fundida flutuante (ZMR da sigla em inglês) da fita microcristalina obtida no passo de CVD. Adicionalmente, foram identificadas as melhores práticas e parâmetros experimentais ideais para os três passos, que possibilitam obter fitas de silício multicristalino de melhor qualidade.
Um novo sistema experimental para a produção de pó de silício com granulometria micrométrica a partir de bolachas de silício multicristalino foi testado, caracterizado e usado na produção de seis pós de silício com intervalos bem definidos de dimensão de partículas, variando entre ≤25 e ]180; 250] μm.
A dimensão das partículas, massa por unidade de área e porosidade são propriedades do substrato de pó que têm uma importante influência no sucesso do processo de CVD e nas propriedades físicas da pré-fita de silício microcristalino crescida sobre o substrato de pó, tais como rácio de pó, taxa de crescimento e porosidade. Foi demonstrado que à medida que a dimensão das partículas do substrato de pó diminui, a taxa de crescimento por CVD aumenta (até 52.8 μm/min) e ambos os valores de porosidade e rácio de pó da pré-fita diminuem (até 52.7 ± 7.3% e 0.60 ± 0.01, respectivamente).
Consequentemente, o êxito do processo ZMR é fortemente afectado pelas características da pré-fita, de tal modo que o material cristalizado de melhor qualidade foi obtido a partir de pré-fitas crescidas sobre substratos de pó com partículas de menor dimensão (≤75 μm), as quais também têm menor porosidade e incorporação de pó do substrato. Foram produzidas fitas de silício multicristalino com sucesso, tendo-se obtido largas áreas cristalinas, medindo aproximadamente 2×4 cm2, com crescimento cristalino colunar e com uma dimensão média do cristal no intervalo de 1 a 10 mm. O valor de resistividade obtido foi 0.70 ± 0.05 Ω.cm, equivalente a uma concentração de dopante de 2.1×1016 cm-3 e o valor obtido para o tempo de vida de portadores minoritários foi de 0.3 ± 0.1 μs.
Foi demonstrada a capacidade de produção de fitas de silício multicristalino, por CVD sobre um substrato de pó, previamente obtido a partir da moagem de pedaços silício, seguido de um passo de recristalização por zona fundida.The Silicon on Dust Substrate (SDS) is a gas-to-wafer process, developed to manufacture multicrystalline silicon ribbons directly from gaseous feedstock (silane), avoiding the standard industry stages of polysilicon deposition, crystal growth and wafering. It aims to achieve good quality material for solar cell manufacturing with a significant reduction of the overall photovoltaic systems cost. The focus of the work presented in this thesis is the improvement of the entire SDS technique, which consists of three main steps: (i) production of silicon powder; (ii) chemical vapour deposition (CVD) of silicon over a silicon powder substrate; and (iii) zone melting recrystallization (ZMR) of the microcrystalline pre-ribbon obtained in the CVD step. Additionally, the best practices and optimal experimental parameters across the three steps were identified. A new experimental setup to produce micrometric sized silicon powders from multicrystalline silicon wafers was tested, characterized and used to manufacture six silicon powders of well-defined particle size intervals, ranging from ≤25 to ]180; 250] μm. The powder substrate properties, such as particle size, mass per unit of area and porosity, have a preponderant influence on the success of the CVD process and the physical characteristics, like powder ratio, growth rate and porosity, of the microcrystalline pre-ribbon grown over the powder substrate. It was demonstrated that as the powder substrate particle size decreases, the CVD growth rate increases (up to 52.8 μm/min) and both pre-ribbon porosity and powder ratio decreases (down to 52.7 ± 7.3% and 0.60 ± 0.01, respectively). The ZMR process performance is substantially impacted by the pre-ribbon physical characteristics, as the best crystallized material was obtained from pre-ribbons grown over powder substrates with smaller particle size (≤75 μm), which also have a lower porosity and powder incorporation from the substrate. Multicrystalline silicon ribbons were successfully produced, having large crystalline areas measuring approximately 2×4 cm2, with visible columnar crystal growth and an average crystal size in the 1 to 10 mm range. The measured resistivity was 0.70 ± 0.05 Ω.cm, equivalent to a dopant concentration of 2.1×1016 cm-3 and a measured minority carrier lifetime of 0.3 ± 0.1 μs. The ability to produce multicrystalline silicon ribbons by CVD over a powder substrate, previously obtained from grinding small silicon chunks, followed by a recrystallization step with a linear molten zone was demonstrated.
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Macdonald, D. "Recombination and Trapping in Multicrystalline Silicon Solar Cells." Phd thesis, 2001. http://hdl.handle.net/1885/47793.
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In broad terms, this thesis is concerned with the measurement and interpretation of carrier lifetimes in multicrystalline silicon. An understanding of these lifetimes in turn leads to a clearer picture of the limiting mechanisms in solar cells made with this promising material, and points to possible paths for improvement. The work falls into three broad categories: gettering, trapping and recombination. A further section discusses a powerful new technique for characterising impurities in semiconductors in general, and provides an example of its application. ¶ ...
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Liu, Anyao. "Precipitation and hydrogenation of iron in multicrystalline silicon." Phd thesis, 2015. http://hdl.handle.net/1885/156242.
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This thesis studies the precipitation and the hydrogenation of dissolved iron in multicrystalline silicon (mc-Si). Photoluminescence imaging is used to obtain both the concentration and the spatial distribution of interstitial iron across mc-Si wafers, with an image resolution of 25 micrometres. In the first part, as-cut mc-Si wafers were examined in order to better understand the internal gettering of iron that occurs during the mc-Si ingot directional solidification process. A simple one-dimensional diffusion-capture model was developed to quantify the gettering process. Relaxation gettering by the grain boundaries was found to be present during ingot cooling, and results indicate that iron must have been super-saturated before the onset of precipitation. A systematic study of the precipitation kinetics of iron in mc-Si was then performed, with respect to the annealing temperature, time, iron super-saturation level, and different types and densities of precipitation sites in mc-Si. Annealing temperatures in the range of 400 - 700C (Celsius degree) were examined in detail. The precipitation of iron approximately follows an exponential decay, which is consistent with the classical Ham's precipitation model. However, the precipitation kinetics were found to demonstrate an increasing dependence on the level of the initial iron super-saturation as the super-saturation level decreases. A higher level of initial iron super-saturation was shown to result in a faster precipitation process. The degree of super-saturation only becomes irrelevant for a high level well above 1000. The dependence of the precipitation kinetics on the initial super-saturation level is likely related to the chemical energy required to initiate the precipitation process. Precipitation of iron was found to occur both at some of the grain boundaries and also at the intra-grain dislocations. The precipitation of iron, at temperatures where the dissolved iron is super-saturated, results in a significant reduction of the interstitial iron concentration by 1 - 2 orders of magnitude. However, the process is inefficient compared to the external gettering of iron via phosphorous diffusion. More importantly, annealing at elevated temperatures leads to a degradation of the mc-Si material quality, which offsets the benefit of the reduced dissolved iron concentration. The last section investigates the impact of hydrogen incorporation on the changes in the interstitial iron concentration and distribution in mc-Si wafers. Hydrogen was introduced into the silicon bulk by annealing wafers with plasma-enhanced chemical vapour deposited silicon nitride films, at 400 - 900C and for minutes to hours. Effective hydrogenation of the interstitial iron was observed. The concentration of interstitial iron was shown to reduce by more than 90% after a 30-minute anneal at 600 - 900C with silicon nitride films. The most effective hydrogenation of iron was found to take place at 700C, where more than 99% of iron was hydrogenated after 30 minutes. Results indicate that the observed reduction in interstitial iron concentration is not caused by an enhanced internal gettering of iron, as some authors suggested. The hydrogenation process is conjectured to be the pairing of positively charged iron with negatively charged hydrogen, forming less recombination active Fe-H complexes in silicon.
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Liu, Yu Chun, and 劉侑群. "Improving the Quality of Multicrystalline Silicon Ingot Dipping Process." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/16037452015435980000.
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Ku, Shih-Tung, and 古世炖. "Research on carbon footprint of multicrystalline silicon solar cell." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/93522727473661386470.
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碩士明新科技大學
工業工程與管理系碩士在職專班
103
Since the industrial revolution, the development of technology and progress created a convenient living life, but the development of science and technology also leads serious environmental pollution. The world is facing climate changes and warming phenomenon. Many studies have shown that emissions of associated human activities have high impact to greenhouse gases, global warming and climate changes. So that environmental issues become more important. Many international organizations began to develop specifications to control carbon emissions, including the "United Nations Framework Convention on Climate Change" and the "Kyoto Protocol" …, etc., to develop carbon dioxide emissions reduction progress. Under supporting of EU regulations, the request to a product with carbon emissions tracing is dramatically increasing, enterprises are facing a new challenge to get sustainable development and reduce the impact of new business. Therefore, while enterprises develop new products, the products must be placed in a low-carbon concept. At this stage, the product life cycle inventory is focused in accordance with ISO 14044, ISO 14064 Greenhouse Gas, Product life-cycle assessment (LCA). Then according to PAS 2050, ISO / TS 14067, the carbon footprint is calculated in order to comply with the relevant regulations and business continuity. In this study, with the cradle-to-gate (C2G) mode, we study the polycrystalline silicon solar cell life cycle to get carbon emission data in order to understand the carbon footprint of the polycrystalline silicon solar cell products. The results show that solar total carbon emissions are 3.192 kgCO2e / piece, ie. 754.141 kgCO2e / kw. Raw material stage contributes the total emissions of 90.147%, 9.853% of the total manufacturing stage of emissions.
47
Phang, Sieu. "Gettering approaches for n-type multicrystalline silicon solar cells." Phd thesis, 2014. http://hdl.handle.net/1885/155810.
Full textAbstract:
The inherent resistance of n-type silicon towards metal contamination can potentially offset the higher metal content of multicrystalline silicon, allowing n-type multicrystalline silicon solar cells to reach high lifetime. Nevertheless, n-type multicrystalline silicon is still affected by metal contaminations and can be further improved by gettering. In terms of the high temperature steps involved, n-type cells require either an additional boron diffusion step or a longer aluminium annealing step to form the p+ emitter region. If not managed carefully, the additional high temperature steps can degrade the lifetime of n-type multicrystalline silicon cells. On the other hand, these additional steps can also be potentially engineered to provide additional gettering effects. This thesis seek to investigate the gettering options available for n-type multicrystalline silicon solar cells. First, the gettering effectiveness of standard phosphorus diffusion, boron diffusion, and aluminium annealing are compared. Results show that all 3 methods considered can be very effective, but the gettering effectiveness of boron diffusion depends on the Boron-Rich Layer (BRL) and is hence very sensitive to the processing conditions. Next, the gettering effect of boron diffusions is investigated in more detail, taking into consideration the trade-off between surface passivation, bulk degradation and gettering effectiveness of BRL. The results show that the gettering effect of the BRL is reversed when oxidised thermally, but is maintained if oxidised chemically using boiling nitric acid. However, the J0e values are lower when the BRL is oxidised thermally instead of chemically, partly due to the lower surface concentration resulting from thermal oxidation. The gettering effectiveness of light phosphorus diffusion overlapping with a deeper boron diffusion, and also the dependence of the gettering effect on the phosphorus concentration were also studied. The results show that the light phosphorus diffusion is effective at gettering, even if only 50nm of the wafer is converted to net n-type doping. In addition, the effect boron diffusion gettering and phosphorus diffusion gettering on sister wafers from n-type multicrystalline silicon ingots were compared. Both diffusion gettering methods resulted in improved average lifetime, with intra-grain lifetime reaching up to 1ms after gettering. However, the gettering on the grain boundaries are less effective, and limits the overall average lifetime. Lastly, we propose a method based on the 2-D continuity equation to reverse the smearing effect caused by lateral carrier diffusion in photoluminescence (PL) images. Since the de-smearing method is very sensitive to the measurement noise, noise filtering methods using smoothing spline, wiener filter, and diffusion smoothing are compared. Furthermore, a method for automatic selection of the noise filter parameter based on the convergence of multiple noisy images is implemented and demonstrated.
48
Chou, Chia-Cheng, and 周家澄. "Quality Deterioration of Multicrystalline Silicon Solar Cell in Transshipment Process." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/ub22c4.
Full textAbstract:
碩士國立東華大學
光電工程學系
100
This study described the deterioration by performance of power, variance of surface and quantum efficiency (QE) in multicrystalline silicon solar cell (mc-Si solar cell) after vibration test which was simulated under the condition of land & air transportation. The vibration test follows some procedures from an unpublished draft of one developing international Standard. Mechanical defects on the surface of solar cell were obviously inspected by recognizable patterns evolving, shown from the method of electroluminescence (EL) imaging. The patterns were classified into 7 types by symptoms of crack/micro-crack. On the other hand, quantum efficiency variances of cell were measured in incident photon-to-electron conversion efficiency (IPCE). In our results, the IPCE performance drop was found indeed in spectrum as 23.7%. After vibration test,we can indicate thatsome specific cells with 3% power loss in I-V measurement. Actually, the total breakage rate is near 1%. The EL images showed the sufficient evidences of defect’s growth due to mc-Si cells experienced vibration response during transshipment simulation. Furthermore, this applied research provided a common vibration test from a pre-normative Standard, and two nondestructive inspection (NDI)methods, EL and QE/IPCE to evaluate the damaged spot on mc-Si solar cells. Result shall also be considered as one key point to improve transportation package as well in the future.
49
Fei, Chih-Chieh, and 費致傑. "Effect of Thermal Annealing On Multicrystalline Silicon For Photovoltaic Applications." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/80033621684656010486.
Full textAbstract:
碩士國立臺灣大學
化學工程學研究所
98
We propose and demonstrate an easy method to remove dislocation limited solar cell performance in multicrystalline silicon solar material. Over 97.5% dislocation density reduction was achieved after annealing at 1350℃ for 6 hours with controlled ambient. The results show that reduction increases with increasing annealing temperature and time. According to the experiment results, the time and temperature factors are the two most important parameters for annealing processes. The mechanism of dislocation reduction is based on pair-wise annihilation which has been categorized as a mechanism of recovery. Moreover, it is evident that the rate limited step is not governed only by thermal activated glide but also by two other modes, cross slip and climb. Lifetime of minority carriers and Fe-B pair concentration are examined by μ-PCD for the case before and after annealing. Minority carrier lifetime decays conspicuously after annealing process because of the increasing concentration of Fei. The reason of Fe-B pair increased should be the precipitate of iron being dissolved during annealing process. Phosphorous gettering process for reducing metal concentration was applied for solving metal dissolving problem. The amount of Fei can be reduced by phosphorous gettering, however, it is still higher than the original level. Internal gettering is found effective only for reducing metal point defects with high mobility in silicon. The existence of metal with low mobility could also deteriorate the lifetime of silicon solar material.
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Cheng, Chao-Yu, and 鄭兆佑. "Study of Multicrystalline Silicon Solar cells with Buried-Contact Structure." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/63720005677558764066.
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