Preparation and Characterization of Mixed Halide MAPbI 3− x Cl x Perovskite Thin Films by Three‐Source Vacuum Deposition

Chloride is extensively used in the preparation of metal halide perovskites such as methylammonium lead iodide (MAPbI 3– x Cl x ), 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 MAPbI 3– x Cl x thin films prepared by three‐source vacuum deposition is presented using methylammonium iodide (MAI), PbI 2 , and PbCl 2 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 MAPbI 3 and MAPbI 3– x Cl x , 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.