Efficiency of GaAs P/Si Two-junction Solar Cells with Multi-Quantum Wells: a Realistic Modeling with Carrier Collection Efficiency

A new structure for III-V on Si two-junction solar cells is proposed with the use of multi-quantum wells (MQWs), reducing the lattice constant of the GaAsP-based top cell and minimizing the thickness of a metamorphic buffer layer between the top cell and the GaP seed layer on Si. The strain-balanced MQWs helps the reduction of As content in the top-cell matrix while extending the absorption edge to a longer wavelength by narrow-gap quantum wells. The efficiency is predicted to be as large as 40% with an entire MQW thinner than 800 nm. The model takes into account the drawbacks of MQWs such as limited light absorption and the bottleneck of carrier collection from the confinement states. This work addresses a new direction toward high-efficiency III-V on Si cells.