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 CsPb₁–_xNb_xI₂Br (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 CsPb₁–_xNb_xI₂Br 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.