Crystal recombination control by using Ce doped in mesoporous TiO2 for efficient perovskite solar cells.

Efficient electron transport layers (ETLs) are the crucial issue for electron transport and hole blocking in organic-inorganic hybrid perovskite solar cells (PSCs). To date, most of the reported effective ETLs have comprised TiO2, which exhibits limited electron mobility and numerous defect states and restricts the enhancement of the performance of PSCs. Hence, the investigation of effective tactics for improving the electronic properties of TiO2 is critical for the fabrication of high-efficiency devices. In this study, a cerium doping method was adopted in mesoporous TiO2, which was prepared via a traditional one-step hydrothermal process, to improve its electron transport properties by recombining nanocrystals and optimizing the negative flat band potential of TiO2. Continuous, aligned and regulated recombined crystals of mesoporous TiO2 were obtained with optimized pathways of electron transport from the ETL to the FTO layer. Moreover, a small amount of Ti4+ ions was replaced by Ce4+ ions in the TiO2 lattice, which led to deformation of the TiO2 lattice and influenced the growth process of TiO2 grains. With an optimized mole proportion of Ce element in the TiO2 precursor, the power conversion efficiency (PCE) of perovskite solar cells was typically boosted to 17.75% in comparison with 15.92% in the case of undoped TiO2.