Solution-processed D-A-p-A-D radicals for highly efficient photothermal conversion

Organic donor-acceptor semiconductors exhibit great potential in photothermal conversion. However, it is still challenging to achieve pure organic materials with broad absorption comparable with inorganic materials such as graphene. Herein, two D-A-D type DPA-BT-O4 and NDI-TPA-O4 and three D-A-& pi;-A-D type Th-O4, Th2-O4, and IDT-O4 were readily prepared via two high-yield steps and simple air oxidization. The stability can be attributed to their multiple resonance structures based on the aromatic nitric acid radical mechanism. Compared with the D-A-D radicals, the conjugation extension of the D-A-& pi;-A-D radicals endows them with a narrowed band gap and broad absorption in powder. Interestingly, the IDT-O4 powder with aggregation-induced radical effect exhibits broad absorption between 300 and 2500 nm, which is comparable with graphene and other inorganic materials. Under irradiation of 0.9 W/cm2 (808 nm), the temperature of IDT-O4 powder rises to 250 & DEG;C within 60 s. The water evaporation conversion efficiency of 94.38 % and an evaporation rate of 1.365 kg/m2 h-1 under one sun illumination were achieved. IDT-O4 stands as one of the most efficient photothermal conversion materials among pure organic materials via a rational design strategy. With an extended & pi;-conjugation skeleton, IDT-O4 powder exhibits broad absorption from 300 to 2500 nm. Its temperature can rise to nearly 250 & DEG;C within 60 s under the irradiation of 0.9 w cm-2. Remarkably, a high water evaporation conversion efficiency of 94.38 % and an evaporation rate of 1.365 kg m-2 h-1 under one sun irradiation are detected.image