Heterojunction Annealing Enabling Record Open‐Circuit Voltage in Antimony Triselenide Solar Cells

Abstract Despite the fact that antimony triselenide (Sb 2 Se 3 ) thin‐film solar cells have undergone rapid development in recent years, the large open‐circuit voltage ( V OC ) deficit still remains as the biggest bottleneck, as even the world‐record device suffers from a large V OC deficit of 0.59 V. Here, an effective interface engineering approach is reported where the Sb 2 Se 3 /CdS heterojunction (HTJ) is subjected to a post‐annealing treatment using a rapid thermal process. It is found that nonradiative recombination near the Sb 2 Se 3 /CdS HTJ, including interface recombination and space charge region recombination, is greatly suppressed after the HTJ annealing treatment. Ultimately, a substrate Sb 2 Se 3 /CdS thin‐film solar cell with a competitive power conversion efficiency of 8.64% and a record V OC of 0.52 V is successfully fabricated. The device exhibits a much mitigated V OC deficit of 0.49 V, which is lower than that of any other reported efficient antimony chalcogenide solar cell.