Radical-activable charge-transfer cocrystals for solar thermoelectric generator toward information conversion

Solar thermoelectric generators (STEGs) that can effectively harvest solar energy and convert it into affordable electricity, provide a promising solution for self-powered wearable electronics and the Internet of Things (IoT). However, their electricity generation is often limited by the low thermal concentration or unstable temperature gradients in practical applications. Herein, we rationally designed an organic radical-activable charge-transfer (CT) cocrystal based on the open-shell radical electron acceptor of 2,6-dibromonaphthalene-1,4,5,8-tetracarboxylic dianhydride. The open-shell radical contributes to the strong near-infrared absorption and nonradiative recombination, resulting in a high photothermal conversion efficiency of 67.2% for the prepared CT cocrystal. Furthermore, the photothermal ink containing the radical-activable CT cocrystal and the transparent resin was successfully coated onto a thermoelectric generator as a cost-effective light absorber, facilely forming a high-performance STEG. Notably, the prepared STEG output a voltage of 143 mV under 1 sun irradiation, demonstrating real-time photodetection capability. We anticipate the potential applications of these cocrystals in self-powered optoelectronics, such as a non-contact and long-distance information converters.