Interface dipole at nickel oxide surface to enhance the photovoltage of perovskite solar cells

Inorganic nickel oxide (NiOx)-based inverted perovskite solar cells (PSCs) are reported to be more stable compared to those using organic hole transport layer materials. However, the Fermi level of NiOx is relatively away from the valence band of perovskite (PVK) layer, causing a large energy level shift at the NiOx/PVK interface and a weak built-in electric field strength. These increase the possibility of recombination, reduce the effective charge collection, seriously affect the efficiency of the device. In this work, an interface dipole with -CF3 end group is anchored to the NiOx/PVK interface, leading to a more matched energy level structure and greatly reducing the energy barrier at the NiOx/PVK interface. Moreover, the addition of Si-CF3 significantly improves the conductivity of NiOx and blunts the defects to large extent. The dipole interlayer significantly improves the built-in electric field and thus increases the photovoltage. Ultimately, the modified device achieves a score of 19.58% efficiency, much better than 17.98% of the control device.