Surface-Reconstructed NiO_x via Solvent-Mediated Engineering for Wide-Bandgap Perovskite Indoor Photovoltaics

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 (CHCl₃) as a solvent-mediated modifier. This treatment simultaneously enhances the Ni³⁺ 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 CHCl₃-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).