Photo-thermo-electric conversion system based on photothermal organic cocrystal composite film for outdoor self-power supply

Abstract

Harvesting sunlight for cost-efficient and environmentally-friendly electricity generation holds significant promise for advancing practical applications of self-powered systems. However, solar-driven thermoelectric generators (STEGs) continue to face the challenge of establishing a stable and substantial temperature gradient across thermoelectric modules for efficient power generation. To address this, we synthesized a photothermal organic charge-transfer (CT) cocrystal, TMPD–PMDA, via a facile solution self-assembly strategy. Strong intermolecular CT interactions endow the cocrystal with a narrow optical bandgap (0.97 eV), a broad absorption spectrum (250–1500 nm), and enhanced non-radiative decay, enabling a temperature rise of 77 °C under one-sun irradiation. By embedding the cocrystal into a polydimethylsiloxane (PDMS) matrix, we fabricated a flexible and customizable composite film (TPF), which reached 89 °C under 1 kW·m⁻² illumination. When employed as a solar absorber in an STEG, the TPF facilitates a pronounced temperature gradient, resulting in an open-circuit voltage of 195 mV, a short-circuit current of 32.7 mA, and a maximum output power density of 1.11 W·m⁻² under one-sun conditions. As a scalable proof of concept, an integrated TPF-based device array operated outdoors successfully enabled temperature monitoring and LED illumination. This work underscores the potential of photothermal CT cocrystals in practical solar energy harvesting and off-grid power applications.