Efficient and stable planar MAPbI3 perovskite solar cells based on a small molecule passivator

Metal halide perovskite solar cells (PSCs) have made remarkable progress recently. However, the large number of defects in the polycrystalline perovskite film has an important impact on the carrier recombination and ion migration in the device. The non-radiative recombination is regarded as the main way of charge loss, which largely determines the performance of PSCs. Here, a small molecule, 2-mercaptopyrimidine (MPM), was selected as the surface passivator for MAPbI3 perovskite films. It is revealed that both S and N atoms in MPM can interact with uncoordinated Pb2+ to passivation the surface defects. As a result, the devices based on MPM passivation achieve a higher power conversion efficiency (PCE) of 19.71% than the control devices (17.85%) due to the reduced surface defect state density. Moreover, MPM-passivated PSCs also possess superior humidity stability, retaining 94% and 82% of the initial PCEs after 720 and 480 h aging in air with a relative humidity of 30% and 60%, respectively.