Component modulation engineering of NiOx hole transport layers in perovskite solar cells by magnetron sputtering

Abstract This study systematically investigates the component modulation of NiOₓ hole transport layers fabricated via reactive magnetron sputtering for high-performance perovskite solar cells. By precisely controlling oxygen flow rates (4–8 sccm) during deposition, we elucidate the interplay between oxygen stoichiometry, crystallographic ordering, defect dynamics, and optoelectronic properties of NiOx films. Structural characterization reveals a critical oxygen threshold (≥6 sccm) for cubic phase crystallization, with X-ray diffraction and X-ray photoelectron spectroscopy analyses demonstrating enhanced crystallinity and increased Ni3+/ Ni2+ ratios under oxygen-rich conditions. Optical studies correlate elevated oxygen flux with bandgap narrowing (3.62–3.45 eV) and transmittance degradation, attributed to Ni3+-mediated mid-gap states and free carrier absorption. Optimized NiOx HTLs deposited at 6 sccm oxygen flow yield PSCs with peak power conversion efficiency of 17.29%, outperforming devices with 4 sccm (17.10%) and 8 sccm (16.64%) counterparts. Accelerated aging tests under thermal (85°C) and light-soaking (AM1.5) stresses reveal superior stability for 6 sccm-optimized devices, retaining 94% and 97.3% of initial PCE after 400 hours, respectively. These findings establish oxygen flux as a critical lever for balancing defect engineering and interfacial energetics, providing a pathway for scalable fabrication of efficient and stable NiOx-based perovskite solar cells.