Self-assembled interlayer aiming at the stability of NiO based perovskite solar cells

Inorganic NiOx based inverted structure perovskite solar cells (PSCs) is reported to be more stable than that with the organic hole transport materials. In this work, NiOx/MAPbI3 interface chemical reaction induced instability of perovskite is unveiled: Ni3+ and I− exhibit redox reactions and deprotonation of MA+ happens, which result in interface defects and perovskite lattice deformation. Thus the defective interface accelerates the degradation of perovskite by defect pathways from the bottom interface to the perovskite surface contacting H2O/O2. Self-assembled interlayer of NH2− end silane on NiOx separates the reactive NiOx and MAPbI3, tunes the interface energy states by –NH2 end group. As a result, the PSC based on the silane treated NiOx achieves enhanced PCE of 20.1% with decent stability under environmental and extreme conditions (high temperature, high humidity, light infiltration). Our work highlights the interface chemical problem induced PSC instability and a simple interface modification to achieve the stable PSCs.