NH <sub>4</sub> PF <sub>6</sub> assisted buried interface defect passivation for planar perovskite solar cells with efficiency exceeding 21%
Xing-Dong Ding, Xiaowen Zhou, Jinwei Meng, Haoxin Wang, Tai‐Sing Wu, Yong Hua, Cheng Chen, Ming Cheng
Abstract
Abstract The buried interface defects severely affect the further enhancements of efficiency and stability of SnO 2 ‐based planar perovskite solar cells (PSCs). To well tackle this problem, we propose a passivation strategy employing NH 4 PF 6 to modify the buried interface of perovskite layer ((FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 composition) in planar PSCs. After introducing NH 4 PF 6 , the oxygen defects on the surface of SnO 2 film are greatly restricted due to the coordinate interaction between fluorine atoms (F) in PF 6 − and undercoordinated Sn 4+ . Meanwhile, the hydrogen bonding interaction (N–H⋯I) between NH 4 PF 6 and PbI 2 can passivate the non‐radiative charge recombination sites, significantly optimizing the quality of perovskite film, as well as the charge transfer process at the SnO 2 /perovskite interface. As a result, the NH 4 PF 6 ‐modified PSC obtains a champion power conversion efficiency (PCE) of 21.11% superior to the reference device (18.46%), and the device with an active area of 1 cm 2 achieves a PCE as high as 17.38%. Furthermore, the unencapsulated NH 4 PF 6 ‐modified PSCs show good humidity stability and retain about 80% of the initial PCE after 1080 h aging at the relative humidity (RH) of 35% ± 5%.