Computational Screening of Indirect-Gap Semiconductors for Potential Photovoltaic Absorbers

Photovoltaic (PV) absorbers are key components of PV cells used to harvest solar energy, which is an attractive renewable energy resource. In this study, a high-throughput computational screening is conducted to discover potential PV absorbers. While direct-gap semiconductors are usually favored as PV absorbers, herein, we focus on indirect-gap semiconductors that could exhibit a long lifetime of photocarriers because of the low probability of band-to-band recombination, enabling high-performance PV cells. From the Materials Project database, we screen semiconductors considering the direct band gap, the difference between the direct and indirect band gaps, and the effective mass of carriers as selection metrics. Taking low costs and earth abundance of constituent elements into account, we suggest GeAs2, SiAs2, and NaSbS2 as particularly promising indirect-gap semiconductors. Their absorption and defect properties are analyzed in detail, providing a route to engineering materials with high efficiency.