Enhanced Efficiency and Stability of All-Inorganic CsPbI2 Br Perovskite Solar Cells by Organic and Ionic Mixed Passivation.

All-inorganic perovskites have been intensively investigated as potential optoelectronic materials because of their excellent thermal stability, especially for CsPbI2 Br. Herein, the authors studied the effects of mixed passivation utilizing organic phenylethylammonium bromide and inorganic ionic cesium bromide (PEABr + CsBr) on the all-inorganic perovskite (CsPbI2 Br) solar cells for the first time. The treatment with different passivation mechanisms enhances the perovskite film quality, resulting in uniform surface morphology and compact film with low trap density. Besides, the passivation improves the energy level alignment, which benefits the hole extraction at the perovskite/HTL interface and drives the interface electron separation, suppressing the charge recombination and realizing a high open-circuit voltage (Voc ). Finally, the device represents a high power conversion efficiency (PCE) of 16.70%, a Voc of 1.30 V, and an excellent fill factor (FF) of 0.82. The Voc loss and high FF should be among the best values for CsPbI2 Br based devices. Furthermore, the treated devices exhibit remarkable long-term stability with only 8% PCE loss after storing in a glove box for more than 1000 h without encapsulation.