Surface‐Reconstructed NiO <i> _x </i> via Solvent‐Mediated Engineering for Wide‐Bandgap Perovskite Indoor Photovoltaics

Abstract Nickel oxide (NiO x ) has been emerged as a highly promising hole‐transport layer (HTL) for inverted perovskite solar cells (PSCs) due to its exceptional operational stability, cost‐effectiveness, and scalability. However, the presence of inherent surface defects in NiO x films (e.g., oxidized species and chemical impurities) leads to significant open‐circuit voltage ( V OC ) losses and severe non‐radiative recombination, particularly pronounced under low‐light conditions. To address these challenges, a facile surface reconstruction strategy is introduced using chloroform (CHCl 3 ) as a solvent‐mediated modifier. This treatment simultaneously enhances the Ni 3+ concentration and hydroxyl group density on the NiO x surface, thereby improving electrical conductivity and providing more bonding sites for the subsequent deposition of the polymeric co‐HTL Poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine]. As a result, wide‐bandgap PSCs incorporating CHCl 3 ‐treated NiO x achieve a power conversion efficiency (PCE) of over 21% under AM 1.5 G illumination, along with an outstanding indoor PCE of 44.74% (steady‐state 42.69%) under LED lighting conditions (1000 lux, 301.9 µW cm −2 and 3 000 K).