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), 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 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.