A Coupled Organic Solar Battery with 12.1% Efficiency

Coupled solar batteries enable direct solar-to-electrochemical energy storage but show low efficiencies due to insufficient solar spectrum utilization. Here, we report the exciton-coupled redox reactions over molecular photoelectrochemical materials for wide-spectrum, high-efficiency, coupled organic solar batteries. The molecular materials are prescreened to match the redox potential with visible light photovoltage for band-edge excitons utilization. The combination of strong donor-acceptor structure with external ion polarization enables long-lived superband gap excitons under ultraviolet light for hot exciton redox reactions, while the incorporation of photothermal molecular motifs further realizes in-band near-infrared energy utilization by the photothermal exciton-photon coupling. A record-high solar-to-electrochemical energy storage efficiency of 12.1% and an exchange photocurrent of 11.2 mA cm^-2 at 0.93 V were achieved under full-spectrum illumination. The long-term stable operation of the manufactured upscalable (∼200 cm²) tandem device under natural sunlight further demonstrates the potential of coupled organic solar batteries as a commercially viable system for practical applications.