Screen-Assisted\nSelf-Spreading of TiO<sub>2</sub> Precursor\nSolution on FTO Substrates for High-Quality Electron Transport Layers\nin Perovskite Solar Cells

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