Molecular-Level Modulation-Induced Charge Transfer in π-d Coordination Polymers for Wearable Solar Thermoelectric Power Generation

Solar-driven electricity generation enables autonomous wearables. Enhancing wearable solar thermoelectric generator (STEG) efficiency requires broadband photothermal materials for synergistic optical and thermal energy concentration. To enhance photothermal performance, we developed a strategy to modify the intramolecular charge transfer capacity by adjusting the ligand charge density. Density functional theory calculations show that this manipulation of the ligand charge density reduces the band gap, resulting in narrow band gaps of 0.715, 0.351, and 0.210 eV for the three coordination polymers (CPs), respectively. This improves solar light absorption and photothermal conversion. Under 1-sun irradiation, the maximum temperature of Cu-BTA (BTA = 1,2,4,5-benzenetetraamine tetrahydrochloride) can reach approximately 70.9 °C. Furthermore, after incorporating Cu-BTA into a photothermal film, the film can reach 74.6 °C under irradiation with 1 sun. Importantly, coating the thermoelectric device with the photothermal film enables it to generate a voltage of 98.2 mV under irradiation with 1 sun. Furthermore, the integrated system reflects changes in human body temperature through voltage changes, enabling real-time health monitoring. This work offers a new way for exploring potential applications in wearable devices.