Facilely synthesized cerium oxide nanocrystals for low-temperature solution-processed and efficient mesoscopic organo-halide perovskite solar cells.

A low-temperature (∼150 °C) mesoporous CeO2 film and compact CeOx layer serve as consecutive electron-transporting layers (ETLs) for PSCs. Optimizing CeO2 nanoparticle size enables a maximum power conversion efficiency of 20.85%, with cerium-based ETLs offering low-cost, effective, stable solutions for high-performance devices.