Lewis Acid–Base Interaction-Induced Porous PbI₂ Film for Efficient Planar Perovskite Solar Cells

The quality of perovskite film is an important factor influencing the photovoltaic properties of solar cells, which is greatly affected by deposition methods. Here, Lewis acid–base interaction-induced porous PbI2 film is obtained by 4-tert-butylpyridine (TBP) vapor treatment method. X-ray diffraction, Raman spectroscopy, and Fourier transform infrared characteristics indicate that a new complex including both TBP and PbI2 molecules was formed by Lewis acid–base reaction. A continuous, uniform, and PbI2-free perovskite film with large grains was obtained from the porous PbI2 reacted completely with CH3NH3I. As a result, a promising power conversion efficiency of ∼18% is achieved in planar-heterojunction perovskite solar cells. Furthermore, via controlling the vapor treatment time, the porosity and thickness of PbI2 film can be readily adjusted, and the unexpected mesoporous perovskite film was first fabricated. Our work demonstrates the preparation of porous PbI2 films by Lewis base vapor treatment for highly efficient planar perovskite solar cells.