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.