Simultaneous passivation on both A and X sites of halogen perovskite with magnesium benzoate.

Surface modification engineering is a well-known effective passivation method for making efficient and stable perovskite solar cells (PSCs). However, to our knowledge, little attention has been paid to simultaneously passivating the A and X sites of halogen perovskites. Herein, we introduced an organometallic salt (CHCOO)Mg (MgBEN) as a passivator, and as a result, the CHCOOMg passivates the A site and CHCOO the X site on the perovskite layer, significantly reducing the trap-state density and nonradiative recombination. Moreover, the modification induces the perovskite film quality to improve, which may decrease the charge accumulation and facilitate carrier transport. By optimizing the concentration of the MgBEN, the perovskite film showed an increased grain size (from 1.18 μm to 1.61 μm), and the best device exhibited an enhanced power conversion efficiency (PCE) of 22.24%. Meanwhile, the device after modification performed with good long-term stability.