Interface engineering of low temperature processed all-inorganic CsPbI2Br perovskite solar cells toward PCE exceeding 14%

All-inorganic perovskite CsPbI2Br has received much attention recently due to its suitable bandgap and excellent thermal stability. Herein, we demonstrated a low temperature solution process to obtain high quality CsPbI2Br films and fabricate devices with a facile n-i-p structure (ITO/SnO2/CsPbI2Br/Spiro-OMeTAD/MoO3/Ag), in which MoO3 was introduced as interfacial layer that led to high efficient charge extraction and suppressed carrier recombination. As a result, the champion cells exhibited a relatively high power conversion efficiency of 14.05% and superb fill factor of 81.5%. More importantly, unencapsulated PSCs with MoO3 interfacial layers showed outstanding stabilities with retaining 80% of initial PCE with thermal treatment at 85 °C for 140 min in ambient air, 80% of initial PCE under continuous illumination for 120 min in ambient air, and 89% of initial PCE after being stored in N2 glove-box over 60 days. Meantime, it should be mentioned that all interlayers and active layer were processed at temperature below 160 °C, and hence, this fabrication technique is promising for flexible energy devices and future commercialization.