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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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High-Speed MOVPE Growth of InGaP Solar Cells
摘要： Impacts of reactor pressure and growth temperature on the qualities and properties of InGaP epitaxial layers grown in a narrow-channel horizontal metalorganic vapor-phase epitaxy (MOVPE) reactor were investigated with a growth rate of 10 μm/h. The roughness of InGaP was improved remarkably when the pressure was increased from 6 to 10 and 15 kPa. The reason is most likely related to the absolute pressure of P and the migrations of In and Ga adatoms on the wafer surface. Owing to the gas-phase reactions and desorption of P from InGaP, the surface of InGaP became rough, and the pit dislocation was increased with an increase in growth temperature. Although a low temperature was beneficial in order to obtain a smooth InGaP surface, the carrier lifetime in InGaP was shortened as a drawback. Consequently, InGaP n-on-p solar cells grown at a low temperature suffered from the degradations of both short-circuit current density and open-circuit voltage. Background impurities and defect densities in low temperature grown InGaP were attributed to these deteriorations. At the optimized growth temperature of 650 °C and the reactor pressure of 15 kPa, the growth rate of InGaP was accelerated to 20 and 30 μm/h. InGaP solar cells were successfully fabricated with the rate of 30 μm/h that opened up the way for the fabrication of III–V multijunction solar cells in the high-speed MOVPE reactor.
关键词： III–V semiconductor materials,semiconductor growth,photovoltaic cells
更新于2025-09-23 15:19:57
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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) - Investigating Industrial Metallization Solutions for Double-side Contact Passivated biPoly Solar Cells
摘要： We present the design and fabrication of suspended optical waveguides on indium phosphide platform for use in an optical buffer device with MEMS actuation, in which the optical delay can be achieved by changing the spacing of the waveguides by electrostatic actuation. The optical and mechanical properties of the waveguides and pillar supports are modeled, and different MEMS actuation schemes are simulated. We also present fabrication and characterization results of the epitaxially grown sample structure and of the suspended waveguide device, exhibiting two parallel waveguides with submicron dimensions separated by a 400-nm air gap, and suspended at 40-μm intervals by S-shaped supports.
关键词： microelectromechanical systems,indium phosphide,optical waveguides,III-V semiconductor materials,optical buffering
更新于2025-09-19 17:13:59
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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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Development of Germanium-Based Wafer-Bonded Four-Junction Solar Cells
摘要： Multijunction solar cells with four junctions are expected to be the next-generation technology for both space and concentrator photovoltaic applications. Most commercial triple-junction solar cells are today grown on germanium, which also forms the bottom subcell. Extending this concept to four junctions with an additional ～1-eV subcell was proven to be challenging. We investigate a new cell concept, which uses direct wafer bonding to combine a metamorphic GaInAs/Ge bottom tandem solar cell with a GaInP/AlGaAs top tandem on GaAs resulting in a monolithic four-junction cell on germanium. This article summarizes results of the cell developments, which have been resulting in a four-junction concentrator cell with 42% ef?ciency. We implemented a new passivated Ge backside technology to enhance the current generation in the Ge junction, and we propose realistic steps to realize solar cells with 45% ef?ciency using this cell architecture.
关键词： photovoltaics,concentrator,photovoltaic cells,germanium,III-V semiconductor materials
更新于2025-09-11 14:15:04