Reproducible One-Step Fabrication of Compact MAPbl(3-x)Cl(x) Thin Films Derived from Mixed-Lead-Halide Precursors

Methylammonium lead trihalide perovskites are attracting intensive interest due to its high photovoltaic performance, low cost and one-step solution processability. Since the morphology of the perovskite thin films play the central role on the cell performance, a plethora of methods have been developed to fabricate uniform perovskite film. Herein, we demonstrate that an innovative approach by applying mixed lead salts (PbI2 + PbCl2) to facilitate reproducible fabrication of compact perovskite thin film. It is proposed that rapid reaction kinetics of PbI2 with MAI enables preformation of perovskite within the intermidiate film matrix, working as homogeneously located domains for squential growth of the PbCl2-derived perovskite. The as-prepared perovskite film exhibited a overall textured crystal morphology and superior compactness, which enables excellent light absorption and long-time preservation of photogenerated charge carriers and therefore exhibits 11% efficiency in planar-structured solar cells. The annealing testing shows the film also possesses very stable morphology upon long-time heating, indicative of the insensitivity of our new protocol to the preparation condition and also the promising thermal stability of its based solar cells. The simplicity of the one-step solution-processing and the high morphology stability of the as-prepared perovskite film endow this mixing lead salts method with feasibility of the large-scale fabrication.