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.

Open-shell Oligo(3,4-dioxythiophene) Radical: Synthesis and Photothermal Conversion Performance

“…In the solution state, the spectra of the two compounds are very similar, because some of the radicals can react with trace water and be converted into hydroxyl compound PTTOH2, while PTTO2 in the film still has the property of open-shell radicals, thus showing strong non-radiation decay and quenching fluorescence. [20,28,55] The results are in good agreement with the previous research results that radical materials usually show extremely low PLQY. Significant inhibition of fluorescence emission by radicals is helpful to enhance photothermal conversion.…”

“…[56] These absorption of PTTOMe2 and PTTO2 are comparable with the graphene, carbon black and Fe3O4 (Figure 2c) and much broader than those of previous pure organic materials (Figure 4a). [17,20,21,55,[57][58][59] The experimental results show that they can absorb most of the UV-vis light and near-infrared light as the PTTOMe2 and PTTO2 powder appear red-black and black, respectively, which is very consistent with the experimental results that the powder absorption spectrum covers the entire solar spectrum. The unique broad absorption in powder promotes PTTOMe2 and PTTO2 to exhibit high photothermal conversion performance.…”

Stable Open-Shell Aromatic Oxalic Acid Radical for Efficient Pho-tothermal Conversion

“…The proposed 2D spin modules are designed based on AIARs through manipulating the electronic spin states of radicals on the benzene ring, thiophene, and other aromatic rings. The ANARs have been prepared in our group and confirmed to have application potential in the fields of photothermal and energy storage [8][9][10][11][12] .…”

“…Based on the open-shell AIAR mechanism, the synthesis and characterization of a series of aromatic nitro acid radicals (ANARs) have been reported [8][9][10]13 . The ANARs with new features that are difficult to achieve by closed-shell molecules, such as outstanding photothermal performance, strong spin concentration, and excellent electrochemical cycling stability 5,[8][9][10]14 .…”

Sulfone-Functionalized Chichibabin’s Hydrocarbons: Stable Diradicaloids with Symmetry Breaking Charge Transfer Contributing to NIR Emission beyond 900 nm

“…Since the pioneering report of the earliest isolable yet highly air-sensitive diradicaloid species called Thiele’s and Chichibabin’s hydrocarbons in the 1900s, organic π-delocalized diradicaloids have fascinated chemists for more than one century. − With their unique open-shell electronic structures, these materials not only hold a significant importance in fundamental chemistry but also exhibit tremendous intriguing physicochemical properties such as intensive low-energy absorption, amphoteric redox behaviors, unique π-magnetisms, and so on. − Therefore, although the stability issue still remains as a major obstacle hampering their future uses, a great number of structurally diverse diradicaloids with relatively long lifetimes under inert environment and even in ambient conditions have been successfully prepared (especially in the past two decades), − demonstrating great potentials for a wide range of applications such as ambipolar organic field-effect transistors (OFETs), organic spintronics, near-infrared (NIR) dyes, batteries, and so on. − …”