Surface Engineering of Ambient-Air-Processed Cesium Lead Triiodide Layers for Efficient Solar Cells

Summary

Cesium lead triiodide (CsPbI₃) presents a desirable band gap, does not require the use of mixed halides for Si tandem solar cells, and possesses relatively high thermal stability owing to its inorganic components. However, the power conversion efficiency (PCE) of CsPbI₃ is lower than that of organic cation-based halide perovskites with identical band gaps. The main factors that govern the PCE of CsPbI₃ are the surface morphology and defect passivation of its thin films on substrates. In this study, we used the sequential dripping of a methylammonium chloride (MACl) solution (SDMS) to obtain highly uniform and pinhole-minimized thin films by controlling the intermediate stages of the crystallization process, followed by surface passivation using octylammonium iodides in ambient air. SDMS accelerated the crystallization process of the CsPbI₃ perovskite layer, resulting in the formation of a uniform and dense surface with few pinholes. Consequently, we fabricated CsPbI₃ solar cells with excellent PCE (20.37%).