High-Efficiency and UV-Stable Planar Perovskite Solar Cells Using a Low-Temperature, Solution-Processed Electron-Transport Layer

Efficient metal-halide perovskite solar cells (PSCs) with a regular structure typically use high-temperature-processed TiO₂ electron-transport layers (ETLs), which suffer from high electron recombination and inherent UV instability. Herein, we present low-temperature solution-processed lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI)-doped C₆₀ (Li-C₆₀) ETLs for high-efficiency and UV-stable planar PSCs with an n-i-p architecture. We found that simple Li-TFSI doping ensured a better energy match between the active layer and the cathode, considerably enhanced the electron mobility of the ETL, and even improved CH₃NH₃PbI₃ crystallization finally to increase the power conversion efficiency (PCE) from 15.3 to 17.8 % with a minor hysteresis effect. Moreover, it was demonstrated that replacing TiO₂ with Li-C₆₀ resulted in PSCs that were much more stable under UV light under an air atmosphere with almost no degradation after 3000 h under a nitrogen atmosphere.