High-Performance Organic Photothermal Material Based on Fusion of the Donor–Acceptor Structure for Water Evaporation and Thermoelectric Power Generation

Recently, organic photothermal materials have shown great application potential for solar-driven water–electricity co-generation. However, their extended application is limited by low solar-heat conversion efficiency. This study designed a planarized donor–acceptor (D–A)-type organic photothermal material 5,18-dibutyl-5,18-dihydrodiquinoxaline[2,3-a:2′,3′-c]phenazine (DDHT) by fusing a strongly electron-donating arylamine unit and strongly electron-withdrawing quinoxalino[2,3-a]phenazine unit. The fused-ring D–A structure not only endowed the material with broad absorption spectra through low-energy intramolecular charge–transfer transition, but also allowed for intense intermolecular π–π interactions, which improve non-radiative transition probability and, correspondingly, the photothermal conversion efficiency (58.58% under laser irradiation at 655 nm). Under a solar intensity of 1 kW m–2, the water evaporation rate was 1.13 kg m–2 h–1 with a solar-to-vapor efficiency of 78.40% for the DDHT-based interfacial evaporation devices. Finally, a solar-driven steam and electricity co-generation device was prepared with the DDHT/wood composite as the solar-evaporator material, demonstrating electricity generation performances and excellent water purification capabilities. Our research found that fused-ring D–A structures are promising organic photothermal systems for efficient solar-heat conversion.