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Assessment of Bulk and Interface Quality for Liquid Phase Crystallized Silicon on Glass
摘要： This paper reports on the electrical quality of liquid phase crystallized silicon (LPC-Si) on glass for thin-film solar cell applications. Spatially resolved methods such as light beam induced current (LBIC), microwave photoconductance decay (MWPCD) mapping, and electron backscatter diffraction were used to access the overall material quality, intra-grain quality, surface passivation, and grain boundary (GB) properties. LBIC line scans across GBs were fitted with a model to characterize the recombination behavior of GBs. According to MWPCD measurement, intra-grain bulk carrier lifetimes were estimated to be larger than 4.5 μs for n-type LPC-Si with a doping concentration in the order of 1016 cm?3. Low-angle GBs were found to be strongly recombination active and identified as highly defect-rich regions which spatially extend over a range of 40–60 μm and show a diffusion length of 0.4 μm. Based on absorber quality characterization, the influence of intra-grain quality, heterojunction interface, and GBs/dislocations on the cell performance were separately clarified based on two-dimensional (2-D)-device simulation and a diode model. High back surface recombination velocities of several 105 cm/s are needed to get the best match between simulated and measured open circuit voltage (Voc), indicating back surface passivation problem. The results showed that Voc losses are not only because of poor back surface passivation but also because of crystal defects such as GBs and dislocation.
关键词： Bulk lifetime,heterojunction,grain boundaries (GBs),two-dimensional (2-D)-device simulation,liquid phase crystallized silicon (LPC-Si),light beam induced current (LBIC)
更新于2025-11-14 15:25:21
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - On the Origin of Silicon Lifetime Degradation During Anneal in III-V Material Growth Chambers
摘要： Silicon bulk lifetime degradation in III-V material growth chambers has been a major hindrance to the development of III-V/Si tandem solar cells. While the exact mechanisms responsible for this degradation remain unknown, many researchers have attributed such degradation to extrinsic contaminants that diffuse into silicon bulk during growth. In this work, we show that thermal activation of grown-in defects in ?oat zone wafers is also a key mechanism behind such degradation. Annealing of the wafer at 1000 ?C to remove these defects, together with a SiNX diffuse barrier layer deposition are both required to preserve the silicon bulk lifetime.
关键词： grown-in defects,diffuse barrier,III-V/Si,silicon bulk lifetime degradation
更新于2025-09-23 15:19:57
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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) - Low-temperature silicon surface passivation for bulk lifetime studies based on Corona-charged Al2O3
摘要： Bulk lifetime studies of crystalline silicon wafers, e.g. with the aim of studying the light-induced degradation and regeneration behavior, require low-temperature surface passivation schemes that do not alter the silicon bulk properties, e.g. through hydrogenation. Aluminum oxide (Al2O3) can provide an excellent and stable surface passivation, however, in order to achieve the best possible surface passivation, an annealing step at ~400°C is typically required, which has been found to alter the bulk properties of some silicon materials. Hence, in this contribution we examine the possibility of passivating the silicon surface using Al2O3 layers that have seen a much lower thermal budget. We demonstrate that we are able to achieve an excellent silicon surface passivation using atomic-layer-deposited Al2O3 with measured effective surface recombination velocities Seff as low as 1.3 cm/s without exceeding a temperature of 250°C. We are able to achieve such excellent low-temperature passivation by applying a post-deposition annealing step at 250°C in combination with the deposition of negative Corona charges on the Al2O3 surface. For samples annealed at only 220°C, we still reach very low Seff values of 2 cm/s after deposition of negative Corona charges. We demonstrate that the Corona-charged low-temperature Al2O3 passivation shows only a slight degradation from an Seff of 1.6 cm/s to an Seff of 5 cm/s after 218 days of storage. Even without any post-deposition anneal and only negative Corona charges deposited, we achieve stable Seff values of 15 cm/s. As an alternative to Corona charging, a short exposure to intense UV light (λ = 395 nm) also significantly improves the surface passivation quality of low-temperature-annealed Al2O3-passivated silicon samples. However, the best surface passivation for the latter method is limited to an Seff value of 6.6 cm/s, which is still quite reasonable for bulk lifetime studies.
关键词： bulk lifetime studies,Al2O3,Corona charging,silicon surface passivation,low-temperature annealing
更新于2025-09-11 14:15:04