Enhanced electron extraction using neodymium ions doped TiO2 for all-inorganic CsPbBr3 perovskite solar cells

The high-quality electron-transport layer (ETL) plays a vital role in boosting the power conversion efficient (PCE) of perovskite solar cells (PSCs). Herein, the lanthanide neodymium (Nd) is used as a dopant to incorporate into the lattice of TiO2 to reduce the trap states and form a n-doping effect, resulting in an increase in electron mobility and conductivity of TiO2, an energy level of TiO2 matching well with that of the perovskite layer. Moreover, the improved wettability of the Nd-TiO2 film enables a fabrication of perovskite light-absorbing layer with high-quality. As a result, the all-inorganic CsPbBr3 PSCs based on Nd-TiO2 ETL achieve a champion PCE of 10.06% owing to the promotion of charge extraction and the inhibition of charge recombination, which is a significantly improved efficiency in comparison with the 6.57% value of the reference cell. Additionally, the target device without encapsulation displays an effectively enhanced stability with over 90% and 80% retention of the original efficiency after aging in ambient air with high humidity (80% RH, 25 °C) for 30 days and under AM 1.5 G illumination at 85 °C for 100 h, respectively.