Indoor NFA‐Organic Photovoltaic for Grid‐Free Water Electrolysis

ABSTRACT Off‐grid hydrogen production via water electrolysis is gaining traction for decentralized energy; however, outdoor solar dependence limits indoor operation. Indoor organic photovoltaics (iOPVs) exhibit high efficiency under artificial illumination and offer a promising power source for such applications. We demonstrate a PM6:Y6‐ based photovoltaic–driven water electrolysis (iOPV–WE) system by integrating optimized OPV devices with a high‐performance oxygen evolution reaction (OER) catalyst. The iOPV devices were engineered using PDINO as the electron transport layer, where thickness optimization (∼6–8 nm) significantly improved charge extraction and reduced interfacial recombination. As a result, the PM6:Y6‐based iOPVs achieved power conversion efficiencies of 12.2% under halogen illumination (1000 lux), while maintaining stable operation in a 30 cm 2 large‐area device. For efficient electrolysis, a Co‐ and Fe‐doped Ni(OH) 2 nanosheet catalyst supported on CuO nanowires (NCF–CuO) was developed, exhibiting a low overpotential of 291 mV at 100 mA cm − 2 and excellent stability. By coupling the optimized iOPV with the NCF–CuO electrode, the integrated system delivered a stable output of ∼1.5 V and 35 mA under halogen illumination (1000 lux), enabling continuous water electrolysis with a Faradaic efficiency of ∼99.2% for O 2 . These results demonstrate the feasibility of indoor solar‐to‐hydrogen conversion using organic photovoltaics.