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.