Performance enhancement of perovskite-sensitized mesoscopic solar cells using Nb-doped TiO₂ compact layer

Perovskite solar cells are one of the most promising alternatives to conventional photovoltaic devices, and extensive studies are focused on device optimization to further improve their performance. A compact layer of TiO₂ is generally used in perovskite solar cells to block holes from reaching the fluorine-doped tin oxide electrode. In this contribution, we engineered a TiO₂ compact layer using Nb doping, which resulted in solar cells with a power conversion efficiency (PCE) of 10.26%, which was higher than that of devices with the same configuration but containing a pristine TiO₂ compact layer (PCE = 9.22%). The device performance enhancement was attributed to the decreased selective contact resistance and increased charge recombination resistance resulting from Nb doping, which was revealed by the impedance spectroscopy measurements. The developed strategy highlights the importance of interface optimization for perovskite solar cells.