Interface Defects Dependent on Perovskite Annealing Temperature for NiO X -Based Inverted CsPbI 2 Br Perovskite Solar Cells.

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 (Ni 3+ 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 CsPbI 2 Br solar cells is reported. That is the Pb 2+ from CsPbI 2 Br perovskites can diffuse into the lattice of NiO X surface as the annealing temperature of perovskites changes. The diffusion of Pb 2+ increases the ratio of Ni 3+ /Ni 2+ 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.