Synergistic Redox Modulation for High-Performance Nickel Oxide-Based Inverted Perovskite Solar Modules

Nickel oxide (NiO_x)-based inverted perovskite solar cells stand as promising candidates for advancing perovskite photovoltaics towards commercialization, leveraging their remarkable stability, scalability, and cost-effectiveness. However, the interfacial redox reaction between high-valence Ni⁴⁺ and perovskite, alongside the facile conversion of iodide in perovskite into I₂, significantly deteriorates the performance and reproducibility of NiO_x-based perovskite photovoltaics. Here, potassium borohydride (KBH₄) is introduced as a dual-action reductant, which effectively avoids the Ni⁴⁺/perovskite interface reaction and mitigates the iodide-to-I₂ oxidation within perovskite film. This synergistic redox modulation significantly suppresses nonradiative recombination and increases the carrier lifetime. As a result, an impressive power conversion efficiency of 24.17% for NiO_x-based perovskite solar cells is achieved, and a record efficiency of 20.2% for NiO_x-based perovskite solar modules fabricated under ambient conditions. Notably, when evaluated using the ISOS-L-2 standard protocol, the module retains 94% of its initial efficiency after 2000 h of continuous illumination under maximum power point at 65 °C in ambient air.