Designing organic charge-transfer (CT) cocrystals for efficient solar-thermal conversion is a long-sought goal but remains challenging. Here we construct a unique CT cocrystal by using persistent 2,2'-azino-bis (3 ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS +• ) as the electron acceptor. The strong persistency and electron affinity of ABTS +• endow a high degree of electron delocalization between ABTS +• and 3,3',5,5'-tetramethylbenzidine donor. Together with the intrinsic long-wavelength absorption of ABTS +• , the synthesized cocrystal can effectively capture the full solar spectrum and show distinguished photothermal efficiency. Such cocrystal is further used for solar-driven interfacial evaporation, and a high evaporation rate of 1.407 kg m -2 h -1 and a remarkable solar-to-vapor efficiency of 97.0% have been achieved upon 1 sun irradiation. This work indicates the enormous prospects for charge transfer-based functional materials through rational radical cations engineering.