Efficient Passivation Strategy on Sn Related Defects for High Performance All‐Inorganic CsSnI3 Perovskite Solar Cells

Abstract Despite remarkable progress in hybrid perovskite solar cells (PSCs), the concern of toxic lead ions remains a major hurdle in the path towards PSC's commercialization; tin (Sn)‐based PSCs outperform the reported Pb‐free perovskites in terms of photovoltaic performance. However, it is of a particularly great challenge to develop effective passivation strategies to suppress Sn(II) induced defect densities and oxidation for attaining high‐performance all‐inorganic CsSnI 3 PSCs. Herein, a facile yet effective thioamides passivation strategy to modulate defect state density at surfaces and grain boundaries in CsSnI 3 perovskites is reported. The thiosemicarbazide (TSC) with SCN functional groups can make strong coordination interaction with charge defects, leading to enhanced electron cloud density around defects and increased vacancy formation energies. Importantly, the surface passivation can reduce the deep level trap state defect density originated from undercoordinated Sn 2+ ion and Sn 2+ oxidation, significantly restraining nonradiative recombination and elongating the carrier lifetime of TSC treated CsSnI 3 PSCs. The surface passivated all‐inorganic CsSnI 3 PSCs based on an inverted configuration delivers a champion power conversion efficiency (PCE) of 8.20%, with a prolonged lifetime over 90% of initial PCE, after 500 h of continuous illumination. The present strategy sheds light on surface defect passivation for achieving highly efficient all‐inorganic lead‐free Sn‐based PSCs.