Efficient Inverted CsPbI 3 Solar Cells with Pb─S Contained Organosulfide‐Halide Perovskite Heterojunction

Here robust Pb‐S covalency is successfully incorporated into CsPbI 3 heterojunction by introducing a new zwitterionic organosulfide‐halide perovskite on top of CsPbI 3 . Cysteamine (CYS: + NH 3 (CH 2 ) 2 S − ) will react with PbCl 2 and form a new 3D perovskite with much shallower fermi level on CsPbI 3 surface, constructing an efficient CsPbI 3 /[CYS][PbCl 2 ] 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 CsPbI 3 perovskite solar cells (PSCs). Besides, the intrinsic moisture and phase stability of [CYS][PbCl 2 ] perovskite will effectively stabilize the CsPbI 3 beneath owing to its robust Pb‐S covalency. PSCs with [CYS][PbCl 2 ] exhibit significantly improved stability, whether in moist air or under continuous maximum power point (MPP) tracking.