The GaAs/GaAs/Si solar cell – Towards current matching in an integrated two terminal tandem

• Published in: Solar energy materials and solar cells Vol. 160; no. C; pp. 94 - 100
• Main Authors: Ren, Zekun, Liu, Haohui, Liu, Zhe, Tan, Chuan Seng, Aberle, Armin G., Buonassisi, Tonio, Peters, Ian Marius
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.2017; Elsevier BV; Elsevier
• Subjects: Absorption; Architecture; Computing time; Energy conversion efficiency; Energy efficiency; GaAs on Si; Gallium arsenide; Group III-V semiconductors; III-V on Si; Matching; One sun tandem solar cell; Photovoltaic cells; Silicon; Solar cells; GaAs on Si; One sun tandem solar cell; III-V on Si
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2016.10.031

Non-concentrating tandem solar cells offer the potential to increase conversion efficiencies beyond 30%. Of particular interest are configurations with a silicon bottom cell – to leverage existing manufacturing infrastructure – and III-V compound semiconductor top cells to combine high efficiencies with long-term stability and experience in applications. In this work we investigate the GaAs/GaAs/Si triple-junction architecture. GaAs and Si form a non-ideal bandgap combination, which poses a challenge to the current matching requirement. As band-to-band absorption in GaAs is almost two thirds of that in Si, absorption can be balanced by replacing the GaAs top junction with a GaAs/GaAs double junction. This opens up a possibility for an integrated two terminal solar cell for the GaAs-Si material system. In this study, we numerically evaluate the efficiency and energy yield potential of the GaAs/GaAs/Si triple-junction architecture. We find that, with state-of-the-art material quality, the GaAs/GaAs/Si architecture has the potential to achieve 33.0% efficiency, and harvesting efficiencies between 31.4% and 32.1%. We fabricated a GaAs/GaAs/Si four-terminal tandem solar cell with a mathematically combined efficiency of 20.4%.