Solution‐processed D‐A‐π‐A‐D radicals for highly efficient photothermal conversion

Abstract 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‐π‐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‐π‐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°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.