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

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 Ni²⁺ 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 cm² 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 cm² device and 22.96% for a 12.96 cm² 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.