Multifunctional pyridinium-based ionic liquid treatment of perovskite for interface engineering and surface defect reduction

Surface passivation has been an effective method to protect the halide perovskite surface. In this work, we adopt the effective one step passivation of surface using new type of ionic liquid, 1-Butyl-4-methylpyridinium hexafluorophosphate. The pyridinium-based ionic liquid treatment facilitates the interface engineering and reduces the non-radiative carrier recombination. The nitrogen atom on pyridinium ring can effectively bond with under-coordinated Pb²⁺ and hence reduce the surface defects. The presence of fluorine atom with bulky organic group enhances the hydrophobicity of perovskite surface leading to enhanced moisture stability. Finally, detailed analysis is carried out on interaction of ionic liquid with lead halide to prove formers passivation effect and hence to be used as a new potential material for perovskite surface passivation. This work paves the way for developing a stable interface environment for perovskites in devices.