Improving the Stability and Monodispersity of Layered Cesium Lead Iodide Perovskite Thin Films by Tuning Crystallization Dynamics

Assembling halide perovskites into layered structures holds promise for addressing chemical and phase stability challenges; however, several other challenges need to be addressed to create efficient and stable halide perovskite devices. Layered halide perovskites (LHPs) suffer from broad distribution of layer thicknesses and bandgaps within thin films. Reducing polydispersity could substantially improve charge transport within LHP films and the performance of LHP-based solar cells. Herein, we focused on layering α-CsPbI3 ((C4H9NH3)2Csn-1PbnI3n+1) thin films. We found that (C4H9NH3)2Csn-1PbnI3n+1 with nominal layer thicknesses of n = 1, 2, 3, and 4 can be deposited at temperatures as low as 100 °C, substantially below the phase transition temperature of bulk α-CsPbI3. Furthermore, we demonstrated that incorporating highly complexing solvents into the precursor solution promotes the formation of intermediate phases within the thin film, slowing down LHP crystallite nucleation, eventually resulting in improv...