Stabilizing Sputtered NiO_x via In Situ Dissociative Adsorption Passivation for Efficient Perovskite Solar Cells

Sputtered nickel oxide (NiO_x) is an industrially compatible hole transport layer for perovskite solar cells (PSCs), yet its practical deployment is limited by interfacial instability arising from disordered Ni³⁺ species and unfavorable reactions with perovskite absorbers. Here, we introduce an in situ dissociative adsorption passivation (IDAP) strategy using bromoacetamide (BAA) to stabilize sputtered NiO_x. In this approach, Br^- ions act as site-blockers by coordinating with surface Ni, suppressing interfacial disorder and stabilizing Ni³⁺ species, while the amide group provides dual anchoring: N-H···O hydrogen bonding strengthens attachment to NiO_x, and the carbonyl group (C═O) passivates the uncoordinated Pb²⁺ located at or near the interface between the NiO_x and the perovskite films. These cooperative efforts reduce trap states, suppress interfacial redox reactions, and mitigate defect-driven degradation under thermal stress. PSCs incorporating BAA-NiO_x achieve a champion power conversion efficiency (PCE) of 26.31% along with a certified PCE of 26.07%, while the larger-area PSCs (1 cm²) maintain 25.48% efficiency. This is one of the highest efficiencies reported for NiO_x-based PSCs. In addition, the encapsulated cell retains 93% of its initial performance after 1500 h of continuous operation.