Synergistic Dual Engineering of NiO _x via Ethylenediamine Chelation and γ‐Ray Irradiation for Enhanced Interfacial Transport in Perovskite Solar Cells

This study highlights an interface-engineering strategy aimed at simultaneously stabilizing nickel oxide (NiO_x) sol-gel solutions and overcoming the intrinsic defects and charge transport limitations of NiO_x. NiO_x has been widely established as an efficient and stable hole transport layer in inverted perovskite solar cells, but sol-gel-based NiO_x is susceptible to defect formation during thermal annealing, leading to non-uniform interfacial contact and limited charge extraction efficiency. To address these issues, ethylenediamine (EDA) chelation and γ-ray irradiation were integrated into the sol-gel NiO_x process to modulate its chemical and electrical properties, followed by the introduction of a MeO-2PACz self-assembled monolayer, thereby improving interfacial ordering and hole extraction. EDA serves as a bidentate chelating ligand, stabilizing metal cations and suppressing premature hydrolysis, thereby modulating the sol-gel chemistry and surface coordination environment of NiO_x and generating an ─OH-rich surface. Subsequently, γ-ray irradiation further modulates the oxidation state of NiO_x within the EDA-modified chemical environment, leading to enhanced p-type conductivity. The resulting surface provides favorable anchoring sites for MeO-2PACz, promoting improved molecular ordering and interfacial energy-level alignment. As a result, the EDA-treated γ-NiO_x/MeO-2PACz composite HTL enables efficient hole extraction, achieving a power conversion efficiency of 24.06% with enhanced operational stability.