Accessing Highly Efficient Photothermal Conversion with Stable Open‐Shell Aromatic Nitric Acid Radicals

Abstract

It is very challenging to prepare stable radicals as they are usually thermodynamically or kinetically unstable in air. Herein, a series of star‐shaped aromatic nitric acid radicals were prepared via facile demethylation and consequent oxidation. As phenol radicals without steric hindrance group protection, they exhibit high electrochemical and thermal stability due to their rich resonance structures including closed‐shell nitro‐like and open‐shell nitroxide structure with unpaired electrons delocalized in conjugated backbones. Among them, TPA‐TPA‐O6 powder exhibited extremely wide absorption from 300 to 2000 nm covering the whole solar spectral irradiance, high photothermal conversion efficiency, and negligible photobleaching effect in seawater desalination. Under the irradiation of one sunlight, the water evaporation efficiency of TPA‐TPA‐O6 is recorded to be as high as 89.41 % and the water evaporation rate is 1.293 kg m−2 h−1, which represents the top performance in pure organic small molecule photothermal materials.

Redox: Organic Robust Radicals and Their Polymers for Energy Conversion/Storage Devices

“…In batteries, radicals can be broadly categorized into two types: one where they are used as electrode active materials, and another where they are utilized as mediators in electrode reactions . With respect to solar cells, a variety of types exist, including dye-sensitized solar cells, organic photovoltaics, and perovskite solar cells. ,,− In these solar cells, radicals are employed to enhance the charge transport layers and improve the chemical stability. As for electric circuits, radicals can be used as electronic conductors or rectifying elements, opening up a wide range of uses .…”

“…Organic radicals, often referred to as free radicals, are highly reactive molecular or atomic species due to the presence of unpaired electrons in the outermost orbitals. , Radicals are usually generated through processes like homolytic bond cleavage, redox reactions, or photolytic processes. ,− Radical molecules are often highly reactive, leading to a wide range of chemical reactions. , They are particularly crucial in processes like oxidation, polymerization, combustion, and various types of biological reactions. ,− Their reactivity stems from their electron deficiency, leading them to partake in reactions that restore stable electron configurations. ,− …”

Observation of reversible light degradation in organic photovoltaics induced by long-persistent radicals

“…51,52 The presence of longpersistent radicals in organic conjugated systems is not an isolated phenomenon. 53,54 In OPV systems, long-persistent radicals were observed in P3HT chloroform solution, which could remain stable for several months. 55 Researchers once utilized electron paramagnetic resonance (EPR) to monitor radicals in OPV polymer donors formed after light ageing or thermal annealing.…”

Near‐Infrared‐I to III Absorption and Emission via Core Engineering of Open‐Shelled Organic Mixed‐Valence Systems

“…Constructing a π ‐conjugate with electron‐donor and electron‐acceptor groups, known as donor–acceptor compounds, or prolongating the molecular conjugation via a large π ‐conjugation are the conventional strategies for fabricating small organic NIR agents. [ 9–17 ] Various small organic molecules, such as BBTD, perylene, porphyrin, BF2, and cyanine derivatives, have been developed as NIR‐II photothermal agents or emitters based on these strategies. [ 15–17 ] Despite significant progress, charge delocalization, or separation in the ground state can strongly influence the degree of electron coupling and lead to the reorganization of molecular orbitals, making it challenging to manipulate the absorption of donor–acceptor compounds.…”