Simultaneous Halides Oxidation Inhibition and Defects Passivation for Efficient and Stable Perovskite Solar Cells

Despite significant progress in improving the photovoltaic efficiency of perovskite solar cells (PSCs), achieving long-term operational stability remains challenging for their commercialization. Light-induced halide ion migration causes instability, oxidizing iodide into iodine. Elevated temperatures exacerbate this issue, resulting in irreversible device degradation. Here, ammonium oxalate (AO) is introduced as an additive to the perovskite precursor to prevent both the degradation of the perovskite precursor and the photo-induced degradation pathway to formamidinium iodide and PbI₂ in perovskite films. AO stabilizes the precursor by inhibiting the oxidation of iodide ions (I^-) and passivates charged traps through coordination and hydrogen bonding interactions, thereby enhancing crystallinity and reducing defects within the resultant perovskite films. This leads to the achievement of a higher-quality perovskite film with a low trap density and an extended carrier lifetime. In addition, the oxidation of I^- within the perovskite film is inhibited, reducing the corrosion of I₂ on the silver electrode and enhancing the long-term operating stability of the photovoltaic device. Consequently, the champion power conversion efficiency (PCE) of PSCs is increased from 22.19% to 24.82%. Meanwhile, the air, thermal, and light stability are also enhanced.