Preparation and Characterization of Mixed Halide MAPbI3−xClx Perovskite Thin Films by Three-Source Vacuum Deposition

Abstract

Chloride is extensively used in the preparation of metal halide perovskites such as methylammonium lead iodide (MAPbI3–xClx), but its persistence and role in solution-processed materials has not yet been rationalized. Multiple-source vacuum deposition of perovskites enables a fine control over thin-film stoichiometry and allows the incorporation of chemical species irrespective of their solubility. Herein, the first example of mixed MAPbI3–xClx thin films prepared by three-source vacuum deposition is presented using methylammonium iodide (MAI), PbI2, and PbCl2 as precursors. The optoelectronic properties of the material are evaluated through photovoltaic and electro-/photoluminescent characterizations. Besides the very similar structural and optical properties of MAPbI3 and MAPbI3–xClx, an increased electroluminescence efficiency, longer photoluminescence lifetimes, as well as larger photovoltage, are observed in the presence of chloride, suggesting a reduction of nonradiative charge recombination.