The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Tonio Buonassisi - One of the best experts on this subject based on the ideXlab platform.
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evolution of letid defects in p type Multicrystalline Silicon during degradation and regeneration
IEEE Journal of Photovoltaics, 2017Co-Authors: Mallory A Jensen, Jasmin Hofstetter, Ashley E Morishige, David Berney Needleman, Tonio BuonassisiAbstract:While progress has been made in developing engineering solutions and understanding light- and elevated temperature-induced degradation (LeTID) in p -type Multicrystalline Silicon (mc-Si), open questions remain regarding the root cause of LeTID. Previously, lifetime spectroscopy of Multicrystalline Silicon (mc-Si) passivated emitter and rear cell semifabricates in the unaffected and the degraded states enabled identification of the effective recombination parameters of the responsible defect. To gain further insight into the root cause of LeTID, in this paper, we measure the injection-dependent lifetime throughout degradation and regeneration and perform lifetime spectroscopy at several time points. Our analysis indicates that the change in lifetime during most of the process can be described by a corresponding change in the concentration of a single responsible defect. We also explore further exposure to light and temperature after nearly complete regeneration and a subsequent dark anneal to demonstrate that the behavior is no longer consistent with LeTID and the same defect is not detected by lifetime spectroscopy at maximum degradation. We consider our results in the context of the proposed hypotheses for LeTID and conclude that both hydrogenation and precipitate dissolution during firing are consistent with our results.
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an insight into dislocation density reduction in Multicrystalline Silicon
Solar Energy Materials and Solar Cells, 2016Co-Authors: Soobin Woo, Tonio Buonassisi, Mariana I Bertoni, Sergio Castellanos, Kwangmin Choi, Seungjin Nam, Douglas M Powell, Hyunjoo ChoiAbstract:Abstract Dislocations can severely limit the conversion efficiency of Multicrystalline Silicon (mc-Si) solar cells by reducing minority carrier lifetime. As cell performance becomes increasingly bulk lifetime–limited, the importance of dislocation engineering increases too. This study reviews the literature on mc-Si solar cells; it focuses on the (i) impact of dislocations on cell performance, (ii) dislocation diagnostic skills, and (iii) dislocation engineering techniques during and after crystal growth. The driving forces in dislocation density reduction are further discussed by examining the dependence of dislocation motion on temperature, intrinsic and applied stresses, and on other defects, such as vacancies and impurities.
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pathway to predict solar cell efficiencies from as grown Multicrystalline Silicon bricks
Photovoltaic Specialists Conference, 2014Co-Authors: Hannes Wagner, Jasmin Hofstetter, Bernhard Mitchell, Ashley E Morishige, Tonio Buonassisi, Pietro P. AltermattAbstract:We present an approach to estimate Multicrystalline Silicon (mc-Si) passivated emitter rear contact (PERC) solar cell efficiencies from as-grown Silicon bricks. The approach is based on interstitial iron concentration Fe i measurements across an as-grown mc-Si brick. Numerical impurity gettering and phosphorus diffusion simulations are used to simulate possible cell fabrication process conditions. The results are then used for numerical device simulations to show the efficiency potential of PERC solar cells across the mc-Si brick. This approach shows a possible pathway to predict final solar cell efficiencies based on characterization of mc-Si materials prior to cell production with state of the art experimental and simulation techniques.
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variation of dislocation etch pit geometry an indicator of bulk microstructure and recombination activity in Multicrystalline Silicon
Journal of Applied Physics, 2014Co-Authors: Sergio Castellanos, Jasmin Hofstetter, Markus Rinio, Maulid Kivambe, Barry Lai, Tonio BuonassisiAbstract:Dislocation clusters in Multicrystalline Silicon limit solar cell performance by decreasing minoritycarrier diffusion length. Studies have shown that the recombination strength of dislocation clust ...
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precipitated iron a limit on gettering efficacy in Multicrystalline Silicon
Journal of Applied Physics, 2013Co-Authors: David P Fenning, Gianluca Coletti, Jasmin Hofstetter, Mariana I Bertoni, Barry Lai, C Del Canizo, Tonio BuonassisiAbstract:A phosphorus diffusion gettering model is used to examine the efficacy of a standard gettering process on interstitial and precipitated iron in Multicrystalline Silicon. The model predicts a large concentration of precipitated iron remaining after standard gettering for most as-grown iron distributions. Although changes in the precipitated iron distribution are predicted to be small, the simulated post-processing interstitial iron concentration is predicted to depend strongly on the as-grown distribution of precipitates, indicating that precipitates must be considered as internal sources of contamination during processing. To inform and validate the model, the iron distributions before and after a standard phosphorus diffusion step are studied in samples from the bottom, middle, and top of an intentionally Fe-contaminated laboratory ingot. A census of iron-silicide precipitates taken by synchrotron-based X-ray fluorescence microscopy confirms the presence of a high density of iron-silicide precipitates both before and after phosphorus diffusion. A comparable precipitated iron distribution was measured in a sister wafer after hydrogenation during a firing step. The similar distributions of precipitated iron seen after each step in the solar cell process confirm that the effect of standard gettering on precipitated iron is strongly limited as predicted by simulation. Good agreement between the experimental and simulated data supports the hypothesis that gettering kinetics is governed by not only the total iron concentration but also by the distribution of precipitated iron. Finally, future directions based on the modeling are suggested for the improvement of effective minority carrier lifetime in Multicrystalline Silicon solar cells.
Daniel Macdonald - One of the best experts on this subject based on the ideXlab platform.
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micrometer scale deep level spectral photoluminescence from dislocations in Multicrystalline Silicon
IEEE Journal of Photovoltaics, 2015Co-Authors: Hieu T Nguyen, Fiacre Rougieux, Fan Wang, Hark Hoe Tan, Daniel MacdonaldAbstract:Micrometer-scale deep-level spectral photoluminescence (PL) from dislocations is investigated around the subgrain boundaries in Multicrystalline Silicon. The spatial distribution of the D lines is found to be asymmetrically distributed across the subgrain boundaries, indicating that defects and impurities are decorated almost entirely on one side of the subgrain boundaries. In addition, the D1 and D2 lines are demonstrated to have different origins due to their significantly varying behaviors after processing steps. D1 is found to be enhanced when the dislocations are cleaned of metal impurities, whereas D2 remains unchanged. Finally, the D4 and D3 lines are proposed to have different origins since their energy levels are shifted differently as a function of distance from the subgrain boundaries.
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Transition-metal profiles in a Multicrystalline Silicon ingot
Journal of Applied Physics, 2005Co-Authors: Daniel Macdonald, Andres Cuevas, Atsushi Kinomura, Y. Nakano, L. J. GeerligsAbstract:The concentrations of transition-metal impurities in a photovoltaic-grade Multicrystalline Silicon ingot have been measured by neutron activation analysis. The results show that the concentrations of Fe, Co, and Cu are determined by segregation from the liquid-to-solid phase in the central regions of the ingot. This produces high concentrations near the top of the ingot, which subsequently diffuse back into the ingot during cooling. The extent of this back diffusion is shown to correlate to the diffusivity of the impurities. Near the bottom, the concentrations are higher again due to solid-state diffusion from the crucible after crystallization has occurred. Measurement of the interstitial Fe concentration along the ingot shows that the vast majority of the Fe is precipitated during ingot growth. Further analysis suggests that this precipitation occurs mostly through segregation to extrinsic defects at high temperature rather than through solubility-limit-driven precipitation during ingot cooling.
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texturing industrial Multicrystalline Silicon solar cells
Solar Energy, 2004Co-Authors: Daniel Macdonald, D.s. Ruby, Andres Cuevas, Mark Kerr, Christian Samundsett, Saul Winderbaum, A LeoAbstract:Abstract Three potential techniques for texturing commercial Multicrystalline Silicon solar cells are compared on the basis of reflectance measurements. Wet acidic texturing, which would be the least costly to implement, produces a modest improvement in reflection before antireflection coating and encapsulation, whereas maskless reactive-ion etching texturing, and especially masked reactive-ion etched ‘pyramids’, generate a larger gain in absorption. After antireflection coating and encapsulation however, the differences between the methods are reduced. Short-circuit current measurements on wet acidic textured cells reveal that there is a significant additional current gain above that expected from the reduced reflection. This is attributed to both light-trapping and oblique coupling of incident light into the cell, resulting in generation closer to the junction.
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trapping of minority carriers in Multicrystalline Silicon
Applied Physics Letters, 1999Co-Authors: Daniel Macdonald, Andres CuevasAbstract:Abnormally high effective carrier lifetimes have been observed in Multicrystalline Silicon wafers using both transient and steady-state photoconductance techniques. A simple model based on the presence of trapping centers explains this phenomenon both qualitatively and quantitatively. By fitting this model to experimental data acquired with a quasi-steady-state photoconductance technique, it is possible to determine the trap density, trap energy, and the ratio between the mean-trapping time and mean-escape time. A correlation between trap density and dislocation density in the material has been found.
Andres Cuevas - One of the best experts on this subject based on the ideXlab platform.
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Transition-metal profiles in a Multicrystalline Silicon ingot
Journal of Applied Physics, 2005Co-Authors: Daniel Macdonald, Andres Cuevas, Atsushi Kinomura, Y. Nakano, L. J. GeerligsAbstract:The concentrations of transition-metal impurities in a photovoltaic-grade Multicrystalline Silicon ingot have been measured by neutron activation analysis. The results show that the concentrations of Fe, Co, and Cu are determined by segregation from the liquid-to-solid phase in the central regions of the ingot. This produces high concentrations near the top of the ingot, which subsequently diffuse back into the ingot during cooling. The extent of this back diffusion is shown to correlate to the diffusivity of the impurities. Near the bottom, the concentrations are higher again due to solid-state diffusion from the crucible after crystallization has occurred. Measurement of the interstitial Fe concentration along the ingot shows that the vast majority of the Fe is precipitated during ingot growth. Further analysis suggests that this precipitation occurs mostly through segregation to extrinsic defects at high temperature rather than through solubility-limit-driven precipitation during ingot cooling.
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texturing industrial Multicrystalline Silicon solar cells
Solar Energy, 2004Co-Authors: Daniel Macdonald, D.s. Ruby, Andres Cuevas, Mark Kerr, Christian Samundsett, Saul Winderbaum, A LeoAbstract:Abstract Three potential techniques for texturing commercial Multicrystalline Silicon solar cells are compared on the basis of reflectance measurements. Wet acidic texturing, which would be the least costly to implement, produces a modest improvement in reflection before antireflection coating and encapsulation, whereas maskless reactive-ion etching texturing, and especially masked reactive-ion etched ‘pyramids’, generate a larger gain in absorption. After antireflection coating and encapsulation however, the differences between the methods are reduced. Short-circuit current measurements on wet acidic textured cells reveal that there is a significant additional current gain above that expected from the reduced reflection. This is attributed to both light-trapping and oblique coupling of incident light into the cell, resulting in generation closer to the junction.
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millisecond minority carrier lifetimes in n type Multicrystalline Silicon
Applied Physics Letters, 2002Co-Authors: Andres Cuevas, Mark Kerr, Christian Samundsett, Francesca Ferrazza, Gianluca ColettiAbstract:Exceptionally high minority carrier lifetimes have been measured in n-type Multicrystalline Silicon (mc-Si) grown by directional solidification and subjected to phosphorus gettering. The highest effective lifetimes, up to 1.6 ms averaged over several grains and 2.8 ms within some of them, were measured for relatively lowly doped, 2–3 Ωcm, wafers. The lifetime was found to decrease for lower resistivities, still reaching 500 μs for 0.9 Ωcm and 100 μs for 0.36 Ωcm. Several important findings are reported here: (i) achievement of carrier lifetimes in the millisecond range for mc-Si, (ii) effectiveness of phosphorus gettering in n-type mc-Si, and (iii) demonstration of good stability under illumination for n-type mc-Si.
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trapping of minority carriers in Multicrystalline Silicon
Applied Physics Letters, 1999Co-Authors: Daniel Macdonald, Andres CuevasAbstract:Abnormally high effective carrier lifetimes have been observed in Multicrystalline Silicon wafers using both transient and steady-state photoconductance techniques. A simple model based on the presence of trapping centers explains this phenomenon both qualitatively and quantitatively. By fitting this model to experimental data acquired with a quasi-steady-state photoconductance technique, it is possible to determine the trap density, trap energy, and the ratio between the mean-trapping time and mean-escape time. A correlation between trap density and dislocation density in the material has been found.
L. J. Geerligs - One of the best experts on this subject based on the ideXlab platform.
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tem studies of oxide and metal silicide precipitation on structural defects in Multicrystalline Silicon grown from metallurgical feedstock
2009Co-Authors: Heidi Nordmark, M. Di Sabatino, Eivind Øvrelid, L. J. Geerligs, John C Walmsley, P Manshanden, Randi HolmestadAbstract:TEM studies of oxide and metal silicide precipitation on structural defects in Multicrystalline Silicon grown from metallurgical feedstock
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Effect of iron in Silicon feedstock on p- and n-type Multicrystalline Silicon solar cells
Journal of Applied Physics, 2008Co-Authors: Gianluca Coletti, R Kvande, Lars Arnberg, V. D. Mihailetchi, L. J. Geerligs, Eivind ØvrelidAbstract:The effect of iron contamination in Multicrystalline Silicon ingots for solar cells has been investigated. Intentionally contaminated p- and n-type Multicrystalline Silicon ingots were grown by adding 53 ppm by weight of iron in the Silicon feedstock. They are compared to reference ingots produced from nonintentionally contaminated Silicon feedstock. p-type and n-type solar cell processes were applied to wafers sliced from these ingots. The as-grown minority carrier lifetime in the iron doped ingots is about 1–2 and 6–20 μs for p and n types, respectively. After phosphorus diffusion and hydrogenation this lifetime is improved up to 50 times in the p-type ingot, and about five times in the n-type ingot. After boron/phosphorus codiffusion and hydrogenation the improvement is about ten times for the p-type ingot and about four times for the n-type ingot. The as-grown interstitial iron concentration in the p-type iron doped ingot is on the order of 1013 cm−3, representing about 10% of the total iron concentra...
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Distribution of iron in Multicrystalline Silicon ingots
Journal of Applied Physics, 2008Co-Authors: R Kvande, Lars Arnberg, Gianluca Coletti, M. Di Sabatino, Eivind Øvrelid, L. J. Geerligs, C. C. SwansonAbstract:The distribution of iron in Multicrystalline Silicon ingots for solar cells has been studied. A p- and a n-type Multicrystalline ingot were intentionally contaminated by adding 53ppmwt (μg∕g) of iron to the Silicon feedstock and compared to a reference p-type ingot produced from ultrapure Silicon feedstock. The vertical total iron distribution was determined by neutron activation analysis and glow discharge mass spectrometry. For the intentionally Fe-contaminated ingots, the distribution can be described by Scheil’s equation with an effective distribution coefficient of 2×10−5. The interstitial iron concentration was measured in the p-type ingots. In the Fe-contaminated ingot, it is almost constant throughout the ingot and constitutes about 50% of the total concentration, which is in conflict with the previous studies. Gettering had a large impact on the interstitial iron levels by reducing the concentration by two orders of magnitude. Considerable trapping was observed at crystal defects on as-cut wafers...
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Transition-metal profiles in a Multicrystalline Silicon ingot
Journal of Applied Physics, 2005Co-Authors: Daniel Macdonald, Andres Cuevas, Atsushi Kinomura, Y. Nakano, L. J. GeerligsAbstract:The concentrations of transition-metal impurities in a photovoltaic-grade Multicrystalline Silicon ingot have been measured by neutron activation analysis. The results show that the concentrations of Fe, Co, and Cu are determined by segregation from the liquid-to-solid phase in the central regions of the ingot. This produces high concentrations near the top of the ingot, which subsequently diffuse back into the ingot during cooling. The extent of this back diffusion is shown to correlate to the diffusivity of the impurities. Near the bottom, the concentrations are higher again due to solid-state diffusion from the crucible after crystallization has occurred. Measurement of the interstitial Fe concentration along the ingot shows that the vast majority of the Fe is precipitated during ingot growth. Further analysis suggests that this precipitation occurs mostly through segregation to extrinsic defects at high temperature rather than through solubility-limit-driven precipitation during ingot cooling.
C Levyclement - One of the best experts on this subject based on the ideXlab platform.
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macropore formation on p type Multicrystalline Silicon and solar cells
Physica Status Solidi (a), 2003Co-Authors: C Levyclement, S Lust, Stephane Bastide, Quang Nam Le, Dominique SartiAbstract:Conditions of macropore formation on Multicrystalline medium doped Silicon were deduced from a systematic study of the macroporous morphology of (100) and (111) oriented monocrystalline Silicon in function of the porous etching parameters and Silicon doping. A new promising method to texturize the surface of Multicrystalline Silicon wafers has been developed which leads to a macroporous surface with a very low effective reflectivity ∼9%. Macroporous Multicrystalline Silicon solar cells exhibit high efficiency larger than 13.5%.
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Multicrystalline Silicon solar cells with porous Silicon emitter
Solar Energy Materials and Solar Cells, 2000Co-Authors: R R Bilyalov, Lieven Stalmans, L Schirone, R. Ludemann, W Wettling, Jef Poortmans, Johan Nijs, G Sotgiu, S Strehlke, C LevyclementAbstract:Abstract A review of the application of porous Silicon (PS) in Multicrystalline Silicon solar cell processes is given. The different PS formation processes, structural and optical properties of PS are discussed from the viewpoint of photovoltaics. Special attention is given to the use of PS as an antireflection coating in simplified processing schemes and for simple selective emitter processes as well as to its light trapping and surface passivating capabilities. The optimization of a PS selective emitter formation results in a 14.1% efficiency mc-Si cell processed without texturization, surface passivation or additional ARC deposition. The implementation of a PS selective emitter into an industrially compatible screenprinted solar cell process is made by both the chemical and electrochemical method of PS formation. Different kinds of Multicrystalline Silicon materials and solar cell processes are used. An efficiency of 13.2% is achieved on a 25 cm 2 mc-Si solar cell using the electrochemical technique while the efficiencies in between 12% and 13% are reached for very large (100–164 cm 2 ) commercial mc-Si cells with a PS emitter formed by chemical method.
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use of porous Silicon antireflection coating in Multicrystalline Silicon solar cell processing
IEEE Transactions on Electron Devices, 1999Co-Authors: R R Bilyalov, Lieven Stalmans, L Schirone, C LevyclementAbstract:The latest results on the use of porous Silicon (PS) as an antireflection coating (ARC) in simplified processing for Multicrystalline Silicon solar cells are presented. The optimization of a PS selective emitter formation results in a 14.1% efficiency Multicrystalline (5/spl times/5 cm/sup 2/) Si cell with evaporated contacts processed without texturization, surface passivation, or additional ARC deposition. Specific attention is given to the implementation of a PS ARC into an industrially compatible screen-printed solar cell process. Both the chemical and electrochemical PS ARC formation method are used in different solar cell processes, as well as on different Multicrystalline Silicon materials. Efficiencies between 12.1 and 13.2% are achieved on large-area (up to 164 cm/sup 2/) commercial Si solar cells.
