Unconventional Route to Oxygen-Vacancy-Enabled Highly Efficient Electron Extraction and Transport in Perovskite Solar Cells

The ability to effectively transfer photoexcited electrons and holes is an important endeavor toward achieving high-efficiency solar energy conversion. Now, a simple yet robust acid-treatment strategy is used to judiciously create an amorphous TiO2 buffer layer intimately situated on the anatase TiO2 surface as an electron-transport layer (ETL) for efficient electron transport. The facile acid treatment is capable of weakening the bonding of zigzag octahedral chains in anatase TiO2, thereby shortening staggered octahedron chains to form an amorphous buffer layer on the anatase TiO2 surface. Such amorphous TiO2-coated ETL possesses an increased electron density owing to the presence of oxygen vacancies, leading to efficient electron transfer from perovskite to TiO2. Compared to pristine TiO2-based devices, the perovskite solar cells (PSCs) with acid-treated TiO2 ETL exhibit an enhanced short-circuit current and power conversion efficiency.