Scalable and conformal nickel oxide for efficient perovskite solar modules

Scalable, conformal nickel oxide (NiO x ) is essential for uniform charge extraction in large-area inverted perovskite modules, yet traditional deposition comes with a trade-off between structural coverage and surface reactivity. Here we report a coordination-regulated strategy based on chemical bath deposition that resolves this bottleneck by governing the NiO x crystallization kinetics. By leveraging the high thermodynamic stability of Ni 2+ –potassium tartrate (Pta) complexes, we suppress disorderly aggregation and halve the hydrolysis rate constant to 0.124 l mol −1  min −1 . This precise kinetic control yields dense and conformal films with refined 4.8-nm nanocrystallites. This nanostructural refinement maximizes the surface density of hydroxyl groups, providing robust anchoring sites where self-assembled monolayers can form a chemically cohesive and defect-suppressed buried interface. Our Pta-NiO x strategy delivers inverted devices with a champion power conversion efficiency of 27.40% (certified reverse-scan power conversion efficiency of 27.35%) and module efficiencies of 23.42% (17.7 cm 2 ) and 21.97% (81.5 cm 2 ). Small-area devices retained 90% of their initial power conversion efficiency after 2,656 h, and 17.7 cm 2 mini-modules retained over 90% after 1,200 h under the ISOS-L-1I protocol.