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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) - Toward >25% Efficient Monolithic Epitaxial GaAsP/Si Tandem Solar Cells
摘要： We report here on progress made in the development of >20% efficient monolithic epitaxial III-V/Si tandem solar cells. Following our prior demonstration of a GaAs0.75P0.25/Si tandem cell with verified AM1.5G efficiency of 20.1%, we have undertaken intensive efforts aimed at optimization of the top and bottom subcells, involving both materials quality improvement and detailed device structure refinement. To date we have thus demonstrated 21.8% AM1.5G GaAs0.75P0.25/Si tandem cells making use of an optimized, but still defect-limited GaAsP top cell combined with a simple diffusion-processed (emitter and back-surface field) Si bottom cell. With recent development of a low dislocation density III-V-on-Si epitaxial materials platform, as well as bottom cell enhancements for photon management, analytical performance loss analysis and efficiency projections indicate that >25% is achievable in the near-term, and 30% within reach with additional holistic optimization.
关键词： photovoltaic cells,Si,III-V semiconductor materials,semiconductor epitaxial layers
更新于2025-09-23 15:21:01
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Investigation of Rear-Emitter GaAs <sub/>0.75</sub> P <sub/>0.25</sub> Top Cells for Application to III–V/Si Tandem Photovoltaics
摘要： A rear-emitter (rear-junction) n-on-p+ device design was investigated for use in metamorphic monolithic III–V/Si tandem solar cells as an alternative to the traditional front-emitter (front-junction) n+-on-p design for potentially greater resistance to threading dislocation-induced performance degradation. A comparison of MOCVD-grown rear- versus front-emitter 1.7-eV bandgap GaAs0.75P0.25 top cell isotypes demonstrated as 30-mV advantage in WOC for the rear-emitter design. This reduction in WOC was determined to be nearly equally caused by a reduction in junction recombination current as well as reduced reverse saturation current from improved quasi-neutral region transport. These results suggest that the rear-emitter design may indeed be a promising pathway for application to metamorphic cells, including III–V/Si tandems, where achieving maximum voltage output is often hindered by elevated dislocation densities. However, further optimization of short-circuit current collection is needed to overcome suboptimal collection probability pro?les that could limit the ef?cacy of such structures.
关键词： semiconductor epitaxial layers,photovoltaic (PV),photovoltaic cells,III–V semiconductor materials
更新于2025-09-12 10:27:22
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Defects and their reduction in Ge selective epitaxy and coalescence layer on Si with semicylindrical voids on SiO<formula><tex>$_{2}$</tex></formula> masks
摘要： Formation of semicylindrical voids on SiO2 masks in Ge layers selectively grown on Si has positive impacts for reduction of threading dislocation density (TDD). Semicylindrical voids are formed through selective epitaxial growth (SEG) and coalescence of SEG Ge layers. A cross-sectional transmission electron microscope (TEM) observation reveals that a threading dislocation (TD) is terminated at a semicylindrical void, resulting in the reduction of TDD. The semicylindrical voids also contribute to the suppression of two-dimensional defects generated at the coalesced interfaces between the SEG Ge layers, which were widely observed in previous reports. Plan-view TEM observations reveal that there are TDs inclined to be parallel to the semicylindrical voids, and plan-view TEM observations show a large (4 μm × 4 μm) TD-free area in the Ge layer with the semicylindrical voids.
关键词： silicon photonics,threading dislocation density,germanium (Ge),semiconductor epitaxial layers,Epitaxial growth
更新于2025-09-10 09:29:36