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AIP Conference Proceedings [Author(s) SILICONPV 2018, THE 8TH INTERNATIONAL CONFERENCE ON CRYSTALLINE SILICON PHOTOVOLTAICS - Lausanne, Switzerland (19–21 March 2018)] - Atom probe Tomography of fast-diffusing impurities and the effect of gettering in multicrystalline silicon
摘要： This article demonstrates an approach for multiscale characterisation of individual defects, such as grain boundaries, in multicrystalline silicon. The analysis techniques range from macroscale characterisation of average bulk lifetime, through photoluminescence to resolve spatial recombination, and finally to nanoscale analysis of the crystallographic characteristics and impurity decoration of the grain boundary using Transmission Kikuchi Diffraction and Atom Probe Tomography. This method can be used to characterise defects and their response to processing, such as gettering and hydrogen passivation. In this paper it is applied to the test case of Saw Damage Gettering on Red Zone High Performance Multicrystalline Silicon. In both as-cast and gettered samples, copper and chromium were observed at a recombination active, random angle grain boundary. After gettering the copper excess was found to decrease. In contrast, the slower diffusing chromium was found to increase, potentially indicating internal gettering. At a recombination inactive Σ3 grain boundary only oxygen was observed at the boundary before gettering, with no transition metals detected.
关键词： multicrystalline silicon,grain boundaries,gettering,impurities,Atom Probe Tomography
更新于2025-11-21 11:20:48
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Low-temperature dark anneal as pre-treatment for LeTID in multicrystalline silicon
摘要： Light and elevated temperature induced degradation (LeTID) is currently a severe issue in crystalline silicon photovoltaics, which has led to numerous efforts to both understand the mechanism and to mitigate it. Here we show that a low-temperature dark anneal performed as the last step in typical solar cell processing influences greatly LeTID characteristics, both the strength of the degradation and the degradation kinetics. While a relatively short anneal in the temperature range of 200–240 °C can be detrimental to LeTID by doubling the degradation intensity, an optimized anneal at 300 °C shows the opposite trend providing an efficient means to eliminate LeTID. Furthermore, we show that the simulated recombination activity of metal precipitation and dissolution during the dark anneal correlates with the experiments, suggesting a possible explanation for the LeTID mechanism.
关键词： PERC,Precipitation,Multicrystalline silicon,Minority-carrier lifetime,LeTID,Copper in silicon
更新于2025-09-23 15:23:52
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Simulation of grain evolution in solidification of silicon on meso-scopic scale
摘要： We present a cellular automata model for computing the grain evolution during directional solidification of silicon on a meso-scopic scale. Firstly, the method is applied to test cases with different shapes of the melt/crystal interface. In a second step we compute the case of an experiment with in-situ observation of the interface shape evolution (Tandjaoui et al., 2012). Here we also include the effect of twinning. The interchanging appearance of two twins could be revisited by our calculations. The probabilities used correspond to those which were analytically derived for an undercooling of 0.6 K (Lin and Lan, 2017). This undercooling is a typical value for a groove with facets (Miller and Popescu, 2017).
关键词： Directional solidification,Cellular automata,Multicrystalline silicon,Lattice Boltzmann methods
更新于2025-09-23 15:23:52
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Development of additive-assisted Ag-MACE for multicrystalline black Si solar cells
摘要： The uniform distribution of silver nanoparticles on the surfaces of diamond-wire sawn multicrystalline silicon (mc-Si) is critical for the texturing of mc-Si by the Ag metal-assisted chemical etching method (Ag-MACE). In this study, an additive containing alkylphenol polyoxyethylene is developed to improve the Ag-MACE process. It enables an even deposition of the silver nanoparticles over the surface of the silicon wafer, so that the entire wafer surface can be uniformly textured with nanostructures. The experimental results show that the additive improves the appearance and performance of solar cells, including their reflectivity, efficiency, internal quantum efficiency and external quantum efficiency. Mass-produced mc-Si solar cells textured using Ag-MACE with this additive have achieved a maximum efficiency of 19.51%, compared with an efficiency of 19.16% for cells fabricated without the additive.
关键词： metal-assisted chemical etching,additive,diamond wire saw,uniform textures,solar cell,multicrystalline silicon
更新于2025-09-23 15:19:57
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Imaging Interstitial Iron Concentrations in Gallium-Doped Silicon Wafers
摘要： In this work, the established method of iron imaging is transferred from B-doped silicon to Ga-doped material. For this purpose, the pairing and splitting conditions are investigated and a preparation procedure suggested that ensures a sufficient fraction of iron–gallium pairing and splitting, respectively. Furthermore the defect parameters available in literature are compared and evaluated for a suitable description of the injection dependent carrier lifetime measurements. A parameter set that enables a coherent and adequate iron evaluation is suggested. Thus, a robust method for spatially resolved determination of the interstitial iron concentration in Ga-doped silicon wafers is presented.
关键词： multicrystalline silicon,defect parameters,photoluminescence,iron imaging,Ga-doped silicon
更新于2025-09-19 17:15:36
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Chemical Texturization Processes for Non-conventional Silicon Substrates for Silicon Heterojunction Solar Cell Applications
摘要： The present work addresses the exhaustive study of the surfaces of multicrystalline silicon wafers after being subjected to a texturization process for silicon heterojunction solar cell applications. The investigations described include the effect that the time of isotropic etching based on combinations of hydrofluoric and nitric acids has on the reflectance, the morphology of the surfaces and the surface recombination through the evolution of the implicit open-circuit voltage. The influence of previous treatments and the elimination of porous silicon or silicon oxide formed on wafer surfaces as a consequence of these texturization processes are also addressed. Textured multicrystalline silicon wafer surfaces with a good uniformity and low weighted hemispherical reflectances (23–24%) have been achieved with short etching times. These texturization processes have also been tested on upgraded metallurgical silicon wafers, resulting in weighted hemispherical reflectance values around 23%, but at the cost of the appearance of important surface defects.
关键词： Multicrystalline silicon,Reflectance,Chemical texturization,Surface morphology,Silicon heterojunction solar cells,UMG silicon
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Hydrogen diffusion from PECVD silicon nitride into multicrystalline silicon wafers: Elastic recoil detection analysis (ERDA) measurements and impact on light and elevated temperature induced degradation (LeTID)
摘要： Hydrogen is a crucial element for crystalline silicon solar cells due to its ability to passivate bulk defects in silicon. The introduction and distribution of hydrogen has gained a lot of interest due to its proposed involvement in the phenomenon termed “light and elevated temperature induced degradation” (LeTID) in multicrystalline silicon (mc-Si) solar cells. LeTID, which can cause an efficiency loss of about 6-14% (relative) for mc-Si PERC (passivated emitter and rear cell) devices upon exposure to elevated temperature and illumination, is a serious cause of concern for the silicon photovoltaic industry. Interaction of hydrogen with mc-Si is complex as mc-Si contains grain boundaries, dislocations, large concentrations of impurities and traps which may affect the diffusivity of hydrogen in silicon. Understanding the diffusion of hydrogen in mc-Si, and how it affects LeTID, is therefore of great interest. In this contribution, the concentration of hydrogen diffused into p-type mc-Si lifetime samples from hydrogen-rich passivation layers (SiNx:H and AlOx:H) fired at different peak firing temperatures is measured by elastic recoil detection analysis (ERDA) along with Rutherford backscattering (RBS). Also, experiments are done to study the impact of annealing in the presence of hydrogen on the extent of LeTID. A correlation is established between the hydrogen concentration diffused into silicon bulk and the extent of LeTID in lifetime samples fired at different peak firing profiles.
关键词： light and elevated temperature induced degradation,multicrystalline silicon wafers,PECVD silicon nitride,elastic recoil detection analysis,Hydrogen diffusion
更新于2025-09-12 10:27:22
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On the Defect Physics Behind Light and Elevated Temperature-Induced Degradation (LeTID) of Multicrystalline Silicon Solar Cells
摘要： State-of-the-art solar cells with passivated surfaces fabricated on block-cast multicrystalline silicon (mc-Si) wafers show a pronounced degradation in efficiency under illumination at elevated temperature, as it typically occurs during operation in a solar module. This effect, frequently named 'Light and elevated Temperature-Induced Degradation' (LeTID), has been attributed to the activation of a specific, hitherto unrevealed bulk defect in mc-Si. Recent experimental results of several labs have indicated that hydrogen is somehow involved in the responsible defect physics, without however providing any direct evidence so far. In this article, we present experimental data unambiguously showing a direct positive correlation of the extent of LeTID with the hydrogen content introduced into the silicon bulk during firing of the silicon wafers coated with hydrogen-rich silicon nitride (SiNx:H) layers. Additional experiments including the pronounced impact of phosphorus gettering on the LeTID extent and the dependence of the degradation and regeneration on the wafer thickness support the involvement of a second species, with most indications pointing towards a metallic impurity. Several approaches of completely avoiding the instability in mc-Si solar cells are derived from the presented defect model, including 1) tuning of the SiNx:H layer properties to minimize the in-diffusion of hydrogen into the wafer and 2) the thinning of the mc-Si wafer, improving the getterability of the metal impurity component toward the surfaces.
关键词： Defects,multicrystalline silicon (mc-Si),solar cells,metallic impurity,degradation,silicon,hydrogen
更新于2025-09-11 14:15:04
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Impact of black silicon on light- and elevated temperature-induced degradation in industrial passivated emitter and rear cells
摘要： Light and elevated‐temperature induced degradation (LeTID) is currently a severe issue in passivated emitter and rear cells (PERC). In this work, we study the impact of surface texture, especially a black silicon (b‐Si) nanostructure, on LeTID in industrial p‐type mc‐Si PERC. Our results show that during standard LeTID conditions the b‐Si cells with atomic‐layer‐deposited aluminum oxide (AlOx) front surface passivation show no degradation despite the presence of a hydrogen‐rich AlOx/SiNx passivation stack on the rear. Furthermore, b‐Si solar cells passivated with silicon nitride (SiNx) on the front lose only 1.5%rel of their initial power conversion efficiency, while the acidic‐textured equivalents degrade by nearly 4%rel under the same conditions. Correspondingly, clear degradation is visible in the internal quantum efficiency (IQE) of the acidic‐textured cells, especially in the ~850 to 1100‐nm wavelength range confirming that the degradation occurs in the bulk, while the IQE remains nearly unaffected in the b‐Si cells. The observations are supported by spatially resolved photoluminescence (PL) maps, which show a clear contrast in the degradation behavior of b‐Si and acidic‐textured cells, especially in the case of SiNx front surface passivation. The PL maps also suggest that the magnitude of LeTID scales with surface area of the texture, rather than wafer thickness that was recently reported, although the b‐Si cells are slightly thinner (140 vs 165 μm). The results indicate that b‐Si has a positive impact on LeTID, and hence, benefits provided by b‐Si are not limited only to the excellent optical properties, as commonly understood.
关键词： passivated emitter and rear cells,multicrystalline silicon,light‐induced degradation,black silicon,solar cells,light‐ and elevated temperature‐induced degradation
更新于2025-09-04 15:30:14