Theoretical Optimization\nof an Earth-Abundant and\nEnvironmentally Friendly Photovoltaic Absorber Cu<sub>3</sub>PSe<sub>4</sub> from First-Principles Study to Device Simulation

To seek an earth-abundant and environmentally friendly\nabsorber\nfor thin-film solar cells, Cu<sub>3</sub>PSe<sub>4</sub> is investigated\nby first-principles calculations and device simulations. We demonstrate\nthat the compound has a suitable band gap width of 1.3 eV as well\nas a high sunlight absorption coefficient. However, drawbacks like\nsmall electron affinity, high hole concentration, large lattice mismatch\nwith CdS, etc., are revealed, which may degrade the photovoltaic performance.\nTo address those shortcomings, we propose (1) to optimize the carrier\nconcentration by preparing the samples at low temperature and under\na Cu-rich environment, (2) to replace the CdS buffer layer by a more\nsuitable wide-gap semiconductor with smaller lattice mismatch, and\n(3) that the selected buffer layer should have small electron affinity\nin order to reduce the open-circuit voltage losses. After implementation\nof these optimization approaches, the device simulations demonstrate\nthat the power conversion efficiency reaches 17.7% for a solar cell\nwith the configuration Mo/Cu<sub>3</sub>PSe<sub>4</sub>/WS<sub>2</sub>/n-ZnO. The combination of first-principles calculations at the atomistic\nlevel and device simulations at the macroscopic level provides an\nappropriate approach to design ideal solar cells.