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

Abstract This study systematically investigates the component modulation of NiO x hole transport layers fabricated via reactive magnetron sputtering for high-performance perovskite solar cells. By precisely controlling O 2 flow rates (4–8 sccm) during deposition, we elucidate the interplay between O stoichiometry, crystallographic ordering, defect dynamics, and optoelectronic properties of NiO x films. Structural characterization reveals a critical O 2 flow (≥6 sccm) for cubic phase crystallization, with XRD demonstrating enhanced crystallinity and XPS showing increased Ni 3+ /Ni 2+ ratios under O-rich conditions. Optical studies correlate elevated O 2 flow with bandgap narrowing (3.62–3.45 eV) and transmittance degradation, attributed to Ni 3+ -mediated mid-gap states and free carrier absorption. Optimized NiO x HTLs deposited at 6 sccm O 2 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 h, respectively. These findings establish O 2 flow as a critical lever for balancing defect engineering and interfacial energetics, providing a pathway for scalable fabrication of efficient and stable NiO x -based perovskite solar cells.