A Facile Preparative Route of Nanoscale Perovskites over Mesoporous Metal Oxide Films and Their Applications to Photosensitizers and Light Emitters

By two-step sequential Pb²⁺ adsorption and reaction with methylammonium-iodide (MAI) or -bromide (MABr) at a low concentration level of 0.06–0.10 m over mesoporous TiO₂ or ZrO₂ film, a well-defined nanoscale CH₃NH₃PbI₃ (MAPbI₃) photosensitizer or CH₃NH₃PbBr₃ (MAPbBr₃) light emitter could be prepared in situ, respectively in a reproducible and atom-economical way. The as-prepared nanoscale perovskites are compared with their thin film counterparts in terms of light absorption/emission, crystallinity, surface morphology, and energy-conversion efficiency. The nanoscale perovskite-decorated films display more transparency than the bulky film due to the much lower amount deposited, while blueshifted and overwhelmingly brighter photoluminescence is observed in the “nano” relative to the “bulk” due to quantum size confinement. Transmission electron microscopy images also clearly show that a few nanometer-sized perovskite dots are deposited homogeneously over the surface of TiO₂- or ZrO₂-particulate film in the course of the current preparative route. When the nano-MAPbI₃ is tested as a photosensitizer in a solid-state dye-sensitized solar cell configuration with a very thin (≈650 nm) TiO₂ mesoporous film, it has a promising initial power conversion efficiency of 6.23%, which outperformed the result of 2.28% from a typical organic molecular dye coded as MK-2.