Interface Defects Dependent on Perovskite Annealing Temperature for NiO_X-Based Inverted CsPbI₂Br Perovskite Solar...

Nickel oxide (NiO_X) is an ideal inorganic hole transport material for the fabrication of inverted perovskite solar cells owing to its excellent optical and semiconductor properties. Currently, the main research on developing the performance of NiO_X-based perovskite solar cells focuses on improving the conductivity of NiO_X thin films and preventing the redox reactions between metal cations (Ni³⁺ on the surface of NiO_X) and organic cations (FA⁺ or MA⁺ in the perovskite precursors) at the NiO_X/perovskite interface. In this study, a new type of interface defects in NiO_X-based CsPbI₂Br solar cells is reported. That is the Pb²⁺ from CsPbI₂Br perovskites can diffuse into the lattice of NiO_X surface as the annealing temperature of perovskites changes. The diffusion of Pb²⁺ increases the ratio of Ni³⁺/Ni²⁺ on the surface of NiO_X, leading to an increase in the density of trap state at the interface between NiO_X and perovskites, which eventually results in a serious decline in the photovoltaic performance of solar cells.