A Coupled Organic Solar Battery with 12.1% Efficiency.

Area of Science:

• Materials Science
• Electrochemistry
• Renewable Energy

Background:

• Direct solar-to-electrochemical energy storage (coupled solar batteries) offers promise but suffers from low efficiencies.
• Current limitations stem from insufficient utilization of the broad solar spectrum.
• Molecular photoelectrochemical materials present a potential avenue for improvement.

Purpose of the Study:

• To develop wide-spectrum, high-efficiency coupled organic solar batteries.
• To enhance solar energy conversion and storage using novel molecular materials and exciton-coupled redox reactions.
• To demonstrate the commercial viability of these advanced solar battery systems.

Main Methods:

• Prescreening molecular materials for optimal redox potential matching with visible light photovoltage.
• Utilizing strong donor-acceptor structures and ion polarization for long-lived superband gap excitons (hot excitons).
• Incorporating photothermal molecular motifs for near-infrared light utilization via photothermal exciton-photon coupling.

Main Results:

• Achieved a record solar-to-electrochemical energy storage efficiency of 12.1%.
• Obtained a high exchange photocurrent of 11.2 mA cm^-2 at 0.93 V under full-spectrum illumination.
• Demonstrated long-term stable operation of an upscalable tandem device (∼200 cm²) under natural sunlight.

Conclusions:

• Exciton-coupled redox reactions over tailored molecular photoelectrochemical materials enable wide-spectrum, high-efficiency solar energy storage.
• The developed coupled organic solar batteries show significant potential for practical, commercially viable applications.
• This approach overcomes previous limitations in solar spectrum utilization for energy storage systems.