Synergistic Passivation of Pyridinium Tetrafluoroborate (PyBF4) in Inverted (CsPbI3)0.05((FAPbI3)1−x(MAPbBr3)x)0.95 Solar Cells with Atomic Layer Deposited NiO Layers

Nickel oxide (NiO) is a promising hole transport layer (HTL) that can be used to fabricate efficient, large-scale inverted-type perovskite solar cells (PSCs). However, depositing a high-quality perovskite layer on NiO substrates comparable to those realized in the normal structure still presents a challenge. Herein, a pyridinium tetrafluoroborate (PyBF₄) additive is introduced to passivate the intrinsic defects in the bulk perovskite films. The nitrogen Lewis base in the PyBF₄ molecule interacts well with uncoordinated Pb²⁺ cations, leading to high-quality perovskite films with minimized defects. Meanwhile, the pseudohalide BF₄⁻ can fill halogen vacancies in the perovskite films to enable defect passivation. As a result, the perovskite precursor solution with PyBF₄ shows better reproducibility for high-efficiency devices. The optimal PSC based on PyBF₄ modification yields a champion power conversion efficiency of 22.7% with atomic layer deposited NiO as the HTL.