Efficient and Stable All-Inorganic Niobium-Incorporated CsPbI₂Br-Based Perovskite Solar Cells

Inorganic cesium lead halide perovskite (CsPbX₃) is a promising light-harvesting material to increase the thermal stability and the device performance as compared to the organic-inorganic hybrid counterparts. However, the photoactive stability at ambient conditions is an unresolved issue. Here, we studied the influence of Nb⁵⁺ ions' incorporation in the CsPbI₂Br perovskite processed at ambient conditions. Our results exhibited that 0.5% Nb-incorporated CsPb_1-NbI₂Br (herein x = 0.005) thin films show excellent uniformity and improved grain size because of the optimum concentration of Nb⁵⁺ doping and hot-air flow. The improved grain size and uniform film thickness deliver a superior interface between the CsPb_1-NbI₂Br layer and the hole-transporting material. The fabricated all-inorganic perovskite solar cell (IPVSC) devices exhibited the Nb⁵⁺ cation incorporation which enables decreased charge recombination, leading to negligible hysteresis. The champion device produces an open-circuit voltage (V_OC) as high as 1.317 V. The IPVSC device containing a CsPb_0.995Nb_0.005I₂Br composition delivers the highest power conversion efficiency of 16.45% under a 100 mW cm^-2 illumination and exhibits a negligible efficiency loss over 96 h in ambient conditions.