High-throughput computational search for high carrier lifetime, defect-tolerant solar absorbers

The solar absorber is a key component in a solar cell as it captures photons and converts them into electron-hole pairs. Its efficiency is driven by the carrier lifetime and the latter is controlled by Shockley-Read-Hall non-radiative processes, which involve defects. Here, we present an ab initio high-throughput screening approach to search for new high-efficiency photovoltaic absorbers taking into account carrier lifetime and recombination through defects. We first show that our methodology can distinguish poor and highly efficient solar absorbers. We then use our approach to identify a handful of defect-tolerant, high carrier lifetime, absorbers among more than 7000 Cu-based known materials. We highlight K3Cu3P2 and Na2CuP as they combine earth-abundance and the potential for high efficiency. Further analysis of our data articulates two challenges in discovering Cu-based solar absorbers: deep anti-site defects lowering the carrier lifetime and low formation-energy copper vacancies leading to metallic behavior. The alkali copper phosphides and pnictides offer unique chemistries that tackle these two issues.