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

The thin film of nickel oxide (NiO_x) 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 NiO_x 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 NiO_x 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 NiO_x, 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 NiO_x 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 NiO_x 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.