Retarding the Growth Kinetics of Chemical Bath Deposited Nickel Oxide Films for Efficient Inverted Perovskite Solar Cells and Minimodules

Abstract The interfacial contact between the hole transport layer (HTL) and perovskite layer plays a critical role in determining the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Herein, to address the limitations of commercial NiO x nanoparticles and realize low temperature fabrication of compact NiO x film, a chemical bath deposition (CBD) approach is employed and strategically modified. By introducing an amino‐alcohol ligand of triisopropanolamine (TPA) into the precursor, the deposition process is effectively controlled. TPA binds strongly with Ni 2+ ions, facilitating their gradual release and promoting the in situ formation of a compact Ni(OH) 2 intermediate. This retarded growth kinetics yield high‐quality NiO x films with enhanced coverage, increased conductivity, and reduced trap‐state. The films also feature abundant hydroxyl groups, providing sufficient anchoring sites for MeO‐2PACz. Based on this bilayer HTL, a PCE of 26.53% (certified 26.44%) with improved operational stability is achieved for the 0.09 cm 2 device, marking the highest efficiency for inverted PSCs based on CBD NiO x . Furthermore, the strategy demonstrates excellent scalability, delivering efficiencies of 24.75% for a 1 cm 2 device and 22.96% for a 12.96 cm 2 minimodule. This work provides a facile but effective CBD approach for preparing high‐quality NiO x films, offering a promising and scalable pathway for inverted PSCs.