High-Quality TiO₂ Electron Transport Film Prepared via Vacuum Ultraviolet Illumination for MAPbI₃ Perovskite Solar Cells

The electron transport layer (ETL) plays an important role in determining the conversion efficiency and stability of perovskite solar cells (PSCs). Here, TiO2 thin film was prepared by irradiating diisopropoxy diacetylacetone titanium precursor thin film with 172 nm vacuum ultraviolet (VUV) at a low temperature. The prepared TiO2 thin film has higher electron mobility and conductivity. As it is used as an ETL for MAPbI(3) PSCs, its band structure is better matched with the perovskite, and at the same time, due to the good interface contact, more uniform perovskite crystals are formed. Most importantly, a large number of hydroxyl radicals were formed during VUV irradiation of the precursor film, which made up for the oxygen defect present on the surface of the TiO2 thin film, and were adsorbed to the film surface. These hydroxyl groups form hydrogen bonds with methylammonium (MA) components on the MAPbI(3) buried surface, thus promoting the transfer of photogenerated electrons at the MAPbI(3)/ETL interface. The power conversion efficiency of PSCs fabricated in air with the ETL prepared by VUV irradiation is 20.46%, which is higher than that of the contrast solar cell based on the sintered ETL (17.96%).