Facile synthesis of hierarchical structured TiO ₂ spheres for high-efficiency mesostructured perovskite solar cells

The formation of an electron transport layer (ETL) in perovskite solar cells (PSCs) plays a significant role in their performance and long-term stability. Researchers have focused on exploring suitable ETL materials with large surface areas and proper nanostructures for developing stable and efficient PSCs. The use of TiO₂ spheres as an ETL in PSCs will help to improve high absorber loading and carrier transport. Herein, the growth of hierarchical structured TiO₂ spheres enhanced device performance and stability owing to better morphology and efficient electron ejection from the absorber layer. Eventually, an averaged maximum power conversion efficiency of 21.3% was attained when 3D hierarchical TiO₂ nanorod-sphere ETLs were employed in PSCs. We believe that our work brings a novel vision for the development and design of highly effective hybrid photovoltaics.