Screen-Assisted Self-Spreading of TiO 2 Precursor Solution on FTO Substrates for High-Quality Electron Transport Layers in Perovskite Solar Cells.

The electron transport layer (ETL) plays a critical role in efficient and stable perovskite solar cells (PSCs). The current effective method for the large-scale preparation of metal oxide ETLs is mainly based on expensive sputtering processes. Here, a screen-assisted self-spreading method is proposed as a novel approach to prepare uniformly thin and conformal TiO 2 films on a rough fluorine-doped tin oxide (FTO) substrate as an ETL in planar PSCs. The TiO 2 ETL deposited by this method exhibited good coverage and homogeneity on the rough FTO substrate, thereby minimizing interfacial recombination. The photovoltaic performance of the PSCs fabricated by this method is superior to that of the cells fabricated by spin coating, especially in terms of the fill factor. The performance enhancement can be attributed to the complete coverage of the FTO substrate by the conformal TiO 2 film, confirming the effectiveness and reliability of the proposed method for the preparation of the TiO 2 ETL. The advantages of this method lie in its scalability to prepare oxide films with a large area, eliminating the requirement of complex equipment, such as spinners, sputters, or physical vapor deposition equipment.