Unraveling Passivation Mechanism of Imidazolium-Based Ionic Liquids on Inorganic Perovskite to Achieve Near-Record-Efficiency CsPbI2Br Solar Cells

A series of 10 imidazolium-based ionic liquids (IILs) with different cations and anions have applied to unravel the passivation mechanism of the IILs on CsPbI 2 Br inorganic perovskites. It is found that anions of IILs play a more important role in passivation of lead- and cesium-related defects in inorganic perovskite compared with imidazole cations because they can form strong ionic interactions (Pb-F, Cs-F). A high-power conversion efficiency of 17.02% is obtained, which is among the highest values of CsPbI 2 Br-based perovskite solar cells.