Photovoltaic-electrochemical devices for solar water splitting: Progress, challenges, and future perspectives

Photovoltaic-electrochemical (PV-EC) systems combine photovoltaic power generation with water electrolysis for solar hydrogen production. This review examines recent progress in III-V, silicon, perovskite, CIGS, and tandem PV-EC technologies. The discussion extends beyond record solar-to-hydrogen (STH) efficiencies to practical factors such as operating conditions, active area, thermal management, durability, hydrogen production, and scale-up. Traditional and integrated configurations are compared, together with their advantages and limitations. Particular emphasis is placed on outdoor operation, large-area demonstrations, and the gap between laboratory performance and practical deployment. The levelized cost of hydrogen (LCOH) is also examined by considering system efficiency, capital and operating costs, component replacement, and lifetime. While perovskite and tandem technologies show high efficiency potential, silicon, CIGS + Si(HJ), and III-V systems have progressed further toward large-area and pilot-scale operation. The review highlights the key barriers to translating high-efficiency PV-EC systems into practical solar hydrogen production.