Donor–Acceptor‐Type Organic‐Small‐Molecule‐Based Solar‐Energy‐Absorbing Material for Highly Efficient Water Evaporation and Thermoelectric Power Generation

Abstract Recently, owing to the great structural tunability, excellent photothermal property, and strong photobleaching resistance, organic‐small‐molecule photothermal materials are proposed as promising solar absorbent materials. Herein, through fusing two strong electron‐withdrawing units dibenzo[ f , h ]quinoxaline and anthraquinone units, a rigid planar acceptor dibenzo[ a , c ]naphtho[2,3‐ h ]phenazine‐8,13‐dione (PDN) with stronger electron‐withdrawing ability is obtained and used to construct donor–acceptor‐type organic‐small‐molecule solar‐energy‐absorbing material, 2,17‐bis(diphenylamino)dibenzo[ a , c ]naphtho[2,3‐ h ]phenazine‐8,13‐dione (DDPA‐PDN). The new compound exhibits a strong intramolecular charge transfer character and conjugates rigid plane skeleton, endowing it with a broadband optical absorption from 300 to 850 nm in the solid state, favorable photothermal properties, high photothermal conversion ability, and good photobleaching resistance. Under laser irradiation at 655 nm, the solid photothermal conversion efficiency of the resulting DDPA‐PDN molecule reaches 56.23%. Additionally, DDPA‐PDN‐loaded cellulose papers equipped with abundant microchannels for water flow are integrated with thermoelectric devices, thus achieving an evaporation rate and voltage as high as 1.07 kg m −2 h −1 and 83 mV under 1 kW m −2 solar irradiation, respectively. This study demonstrates the application of photothermal organic‐small‐molecules in water evaporation and power generation, therefore offering a valuable prospect of their utilization in solar energy harvesting.