The moisture instability of perovskite materials especially under illumination has engendered severe hindrance toward future industrial applications for high-efficiency and stable perovskite solar cells. Here, we designed and synthesized a series of hydrophobic alkyl bisphosphonic molecules which served as interfacial layers between a perovskite and PC 61 BM to improve the moisture and light-stability of the inverted PVSCs. The steric arrangement of the bisphosphonic molecules suppressed the infiltration of moisture and oxygen inside the perovskite film under humidity and continuous illumination, and decreased the loss of halide and methylammonium ions as revealed by the lower PbI 2 and Pb 0 in the film. When exposed to 50-60% RH and continuous AM1.5G illumination, devices after undergoing interfacial treatment retained 70% of the initial power conversion efficiency, while the control device totally failed, suggesting markedly improved moisture and light-stability by the interfacial engineering.Moreover, the treated devices showed almost no degradation after being stored in an ambient atmosphere for 300 h.

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