Efficient and Stable Chemical Passivation on Perovskite Surface via Bidentate Anchoring

Chemical passivation is an effective approach to suppress the grain surface dominated charge recombination in perovskite solar cells (PSCs). However, the passivation effect is usually labile on perovskite crystal surface since most passivating agents are weakly anchored. Here, the use of a bidentate molecule, 2-mercaptopyridine (2-MP), to increase anchoring strength for improving the passivation efficacy and stability synchronously is demonstrated. Compared to monodentate counterparts of pyridine and p-toluenethiol, 2-MP passivation on CH3NH3PbI3 film results in twofold improvement of photoluminescence lifetime and remarkably enhanced tolerance to chlorobenzene washing and vacuum heating, which improve the power conversion efficiency of n-i-p planar structured PSCs from 18.35% to 20.28%, with open-circuit voltage approaching 1.18 V. Moreover, the CH3NH3PbI3 films passivated with 2-MP exhibit unprecedented humid-stability that they can be exposed to saturated humidity for at least 5 h, mainly due to the passivation induced surface deactivation, which renders the unencapsulated devices retaining 93% of the initial efficiency after 60 days aging in air with relative humidity of 60-70%.