Reduction of Nonradiative Recombination in Sb 2 Se 3 Thin Films by Heat Treatment Under Sulfur Atmosphere

Antimony selenide (Sb 2 Se 3 ) thin films have attracted significant interest for developing low‐cost, hazardous‐element‐free photovoltaic technology. While the initial progress in Sb 2 Se 3 solar cells was rapid, the growth of power conversion efficiency slowed down. High open‐circuit voltage ( V OC ) deficit is recognized as the critical performance‐reducing factor, barely reaching 50% of the radiative limit even in the record‐efficiency solar cells. In this article, using heat treatment under sulfur atmosphere and Cl‐doping, we investigate passivation strategies by measuring photoluminescence (PL) emission. We show that the PL response was strongly enhanced after the S‐treatment and correlated with the level of incorporated S. From absolute PL measurements, a quasi‐Fermi‐level splitting of 562 meV was achieved in Cl‐doped Sb 2 Se 3 thin films and annealed under optimal conditions. This article provides a technological route for reducing nonradiative recombination in Sb 2 Se 3 which is a highly encouraging process for mitigating V OC deficit in Sb 2 Se 3 solar cells.