High purity and crystalline thin films of methylammonium lead iodide perovskites by a vapor deposition approach

Highlights: • High-purity perovskite films can be prepared by a vapor deposition approach. • Thin film deposition is controlled by the molar flow rate of perovskite sources. • Stoichiometric flow rates of both reactants are achieved by using Knudsen cells. • Compact, uniform, stable and crystalline perovskite thin films were produced. - Abstract: A procedure for the physical vapor deposition (PVD), in high-vacuum conditions, for high purity and crystalline methylammonium lead halide perovskite thin films is described. This procedure and methodology can be used to fabricate high-performance hybrid organic-inorganic materials that have recently emerged as the next-generation photovoltaic technology. PVD of methylammonium iodide and lead iodide to produce lead halide perovskite thin films was optimized according to the equilibrium vapor pressures of corresponding precursors evaporated from Knudsen effusion cells. Optical properties of perovskite thin films were characterized by UV-Vis-NIR and fluorescence spectroscopy. The high crystallinity of vapor-deposited thin films on glass, indium tin oxide, fluorine-doped tin oxide, and TiO₂ surfaces was proved by scanning electron microscopy and X-ray diffraction. This vapor deposition approach leads to the production of very pure, crystalline and high stable perovskite thin films.