Interfacial modification of NiOx by self-assembled monolayer for efficient and stable inverted perovskite solar cells

NiOx as a hole transport material for inverted perovskite solar cells (iPSCs) has received great attention owing to its high transparency, low fabrication temperature, and superior stability. However, the mismatched energy levels and possible redox reactions at the NiOx/perovskite interface severely limit the performance of NiOx-based iPSCs. Herein, we introduce a p-type self-assembled monolayer (SAM) between NiOx and perovskite layers to modify the interface and block the undesirable redox reaction between perovskite and NiOx. The SAM molecules all contain phosphoric acid function groups, which can be anchored onto the NiOx surface and passivate the surface defect. Moreover, the introduction of SAMs can regulate the energy level structure of NiOx, reduce the interfacial band energy offset, and hence promote the hole transport from perovskite to NiOx layer. Consequently, the device performance is significantly enhanced in terms of both power conversion efficiency (PCE) and stability.