Donor-Acceptor Radicaloid Materials with Enhanced Nonradiative Decay Enable Efficient Solar-Thermal Conversion

Organic photothermal materials are promising for solar-driven water purification and thermoelectric energy harvesting, yet their practical deployment is frequently limited by insufficient solar utilization, suboptimal photothermal conversion, and photobleaching under prolonged irradiation. Here, we report TBT-ThT-O, a donor-acceptor small molecule in which a strong D-π-A-π-D framework, π-bridge extension, and radical character act cooperatively to enhance intramolecular charge transfer and suppress radiative decay, thereby favoring nonradiative heat dissipation under sunlight. TBT-ThT-O exhibits broadened solar absorption extended to 2000 nm and excellent photothermal stability. When immobilized in porous polyurethane foam to construct an interfacial evaporator, TBT-ThT-O@PU achieves a high evaporation rate of 1.356 kg m-2 h-1 and a solar-to-vapor efficiency of 93.05% under 1 sun. As a photothermal coating coupled with a thermoelectric module, the system delivers a voltage of 245 mV and an output power density of 3.936 W m-2 under 1 sun. Furthermore, a lens-assisted hybrid platform is demonstrated to intensify outdoor solar flux for simultaneous freshwater production and electricity generation. This work demonstrates that D-A radicaloid molecular engineering provides a viable route to stable, high-performance organic photothermal materials for integrated solar desalination and power generation.