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 CH3 NH3 PbI3 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.