A Codoping Strategy for Efficient Planar Heterojunction Sb₂S₃ Solar Cells

Abstract Antimony sulfide is a promising wide bandgap light‐harvesting material owing to its high absorption coefficient, nontoxicity, superior stability, and low cost. However, the reported Sb₂S₃ absorber suffers from complicated defect characteristics due to its quasi‐1D structure. Herein, a codoping technique from chlorine and selenium is developed in hydrothermal method to regulate the film defect properties and promote the device efficiency. The theoretical calculation and experimental results demonstrate that the Cl&Se codoping plays a synergistic role in absorber film quality improvement. Se doping could efficiently fill the intrinsic deep defect level V_S and Cl is a benign n‐type dopant and favor [hk1] oriented deposition. Systematic device physical characterizations verify the codoped device superior heterojunction quality and much lower interface and bulk defect density comparing with control one. The optimal codoping device delivers a certified power conversion efficiency of 7.15% (5.9% for control one), the highest certified value in planar Sb₂S₃ solar cells. This study develops an effective doping strategy with multi‐element synergistic incorporation which sheds new light on high‐efficiency Sb₂S₃ solar cells.