Smooth perovskite thin films and efficient perovskite solar cells prepared by the hybrid deposition method

We provide details on the development of instrumentation and methodology to overcome the common difficulties that the vacuum-related techniques face for fabrication of perovskite thin films and perovskite solar cells (PSCs). Our methodology relies on precisely controlling the flow of methylammonium iodide (CH₃NH₃I, MAI), which has a high-vapor pressure nature, and the deposition rate of metal halides (PbCl₂ or PbI₂). This hybrid deposition method allows the growth of perovskite films with smooth surface, good crystallinity, high surface coverage, uniform chemical composition and semi-transparency. We also systematically investigated the effects of the evaporation source materials (PbCl₂ : MAI versus PbI₂ : MAI), substrate temperatures, and post-annealing on the properties of perovskite films, as well as device performances based on this method. By employing a thin perovskite film (<200 nm), the power conversion efficiency of PSC can be as high as 11.5%.