Thermopower amplification in thermogalvanic cells via radiative cooling-mediated photothermal conversion

Emerging quasi-solid-state thermogalvanic cell (TGC) hold promise for low-grade heat harvesting. Harnessing solar energy to generate electricity through TGCs is limited by the challenge of maintaining a large temperature gradient (Δ T ) under illumination. Herein, we report an enhanced-performance photothermoelectric TGC by synergistically integrating localized photothermal (PT) heating with passive radiative cooling (RC), spontaneously establishes a robust ΔT on the bacterial cellulose-based TGC under illumination, enabling efficient photothermoelectric conversion. The flexible device featured an asymmetrically coated structure, employing carbon nanotubes and titanium dioxide as PT and RC functional layers. The optimized device achieved a Δ T of 14.11 K under 1 sun illumination, producing a voltage of 18.07 mV, substantially exceeding that of the PT-only counterpart. It delivers a maximum power density of 13.98 mW m −2 , a 214% enhancement attributed to effective suppression of parasitic heating. A practical outdoor application scenario was demonstrated, highlighting its potential as a self-powered device. As a proof-of-concept, the device has been developed as an intelligent light-control switch for smart windows aided by a voltage amplifier. By harnessing sunlight not only as a heat source but also as a trigger for asymmetric thermal management, this work achieves maximized Δ T in solar-driven TGCs, enabling a potential platform that integrates energy harvesting, environmental sensing, and responsive control.