Enhanced performance of p-i-n perovskite solar cell via defect passivation of nickel oxide/perovskite interface with self-assembled monolayer

[Display omitted] •3-(Triethoxysilyl)propylamine (TSPA) is introduced as a surface modifier of nickel oxide (NiOx).•TSPA form a self-assemble monolayer with positive surface dipole on the NiOx surface.•TSPA passivate hydroxyl group on the surface of the NiOx and improve defect passivation.•TSPA promote batter energy level alignment and charge transportation/extraction capabilities.•NiO/TSPA based PSCs shows a higher cell-efficiency and better stability. The thin film of nickel oxide (NiOx) nanoparticles was successfully applied as the hole transporting layer (HTL) in inverted (p-i-n) perovskite solar cells (PSCs), but inevitable surface defects and hydroxyl groups present on the NiOx surface are limiting of performance and stability improvements. For overcome these problems, we introduce 3-(Triethoxysilyl)propylamine (TSPA), self-assembly molecule, as an interfacial modifier between NiOx and perovskite film to attenuate the surface defect and prevent deterioration caused by direct contact of the hydroxyl groups and the perovskite. Self-assembled monolayer is formed by hydrogen-bond between amino group of TSPA and hydroxyl group on the surface of the NiOx, which passivate surface and reduce defect density. In addition, a positive dipole was formed by the TSPA monolayer, which resulted in deeper work function at the NiOx interface and improved energy level alignment in PSCs, improving charge extraction-transportation capabilities and reducing recombination of charge carriers at the interface. In consequence, PSCs based on NiOx with TSPA monolayer have boosted PCE by up to 20.21% and showed long-term stability over 60 days under ambient air and varying humidity condition. This approach is expected to be further advanced as one of the methods for the development of high-performance PSCs.