Efficient Inverted CsPbI₃ Solar Cells with Pb─S Contained Organosulfide‐Halide Perovskite Heterojunction

Abstract Here robust Pb‐S covalency is successfully incorporated into CsPbI₃ heterojunction by introducing a new zwitterionic organosulfide‐halide perovskite on top of CsPbI₃. Cysteamine (CYS: ⁺NH₃(CH₂)₂S⁻) will react with PbCl₂ and form a new 3D perovskite with much shallower fermi level on CsPbI₃ surface, constructing an efficient CsPbI₃/[CYS][PbCl₂] heterojunction. As a result, interfacial energy loss can be significantly inhibited and device open‐circuit voltage (Voc) is increased to over 1.20 V with champion efficiency of 20.38% in inverted CsPbI₃ perovskite solar cells (PSCs). Besides, the intrinsic moisture and phase stability of [CYS][PbCl₂] perovskite will effectively stabilize the CsPbI₃ beneath owing to its robust Pb‐S covalency. PSCs with [CYS][PbCl₂] exhibit significantly improved stability, whether in moist air or under continuous maximum power point (MPP) tracking.