Cuprous Halide Coordination Polymer for Efficient NIR-I Photothermal Effect and Photo-thermo-electric Conversion

Photo-thermo-electric conversion devices represent a promising technology for converting solar energy into electrical energy. Photothermal materials, as a critical component, play a significant role in efficient conversion from solar energy to thermal energy and subsequently to electrical energy, thereby directly influencing the overall system's solar energy utilization efficiency. However, the application of single-component photothermal materials in photo-thermo-electric conversion systems remains limited. The exploration of novel photothermal materials with broad-spectrum absorption, high photothermal conversion efficiency (PCE), and robust output power density is highly desired. In this study, we investigated a black cuprous halide compound, [Cu2Cl2PA]n (1, PA = phenazine), which exhibits broad-spectrum absorption extending into the near-infrared (NIR) region. Compound 1 demonstrated a high NIR-I PCE of 50% under irradia-tion of an 808 nm laser, attributed to metal-to-ligand charge transfer (MLCT) from Cu(I) to PA ligands and strong intermolecular π–π interactions among PA ligands. Furthermore, the pho-to-thermo-electric conversion device constructed using compound 1 achieved a notable output voltage of 261 mV and an output power density of 0.92 W/m² under the 1 Sun (1000 W/m²) xenon lamp.