Stable and highly efficient all-inorganic CsPbBr3 perovskite solar cells by interface engineering with NiO NCs modification

The existence of considerable energy level differences and defects at interfaces between the CsPbBr3 film and the carbon electrode, have been critical bottlenecks to restrict the development of the photoelectric conversion ef-ficiencies (PCEs) of all-inorganic CsPbBr3 perovskite solar cells (PSCs). Therefore, to solve this contradiction, the interface engineering has been applied into the interface of CsPbBr3/carbon through many passivators. However, most of the passivators reported previously are composed of organic ingredients, which is inconsistent with the concept of the "real all-inorganic" PSCs. Here, NiO nanocrystals (NiO NCs) with hole transporting behaviors were prepared by hydrothermal synthesis method and applied to modify the interface between the CsPbBr3 film and carbon electrode. After NiO NCs modified, the CsPbBr3 film with a smoother surface exhibits suppressed interface defects and appropriate interfacial energy band alignment, thereby decreasing the carrier recombination and improving the charge extraction ability. Eventually, by optimizing the concentrations of NiO NCs and the spin -coating cycles of CsBr methanol solution, the NiO NCs-treated device generates a champion efficiency of 9.19% with a short-circuit current (JSC) of 7.57 mA cm-2, an open-circuit voltage (VOC) of 1.57 V and a fill factor (FF) of 77.44%, in comparison with the pristine device with an inferior efficiency of 7.15%, a JSC of 6.92 mA cm-2, a VOC of 1.48 V and an FF of 69.64%. Furthermore, the NiO NCs modified devices show no significant degradation after 30 days in open-air conditions.