Breakthrough in organic radical crystals boosts solar power-to-electricity tech
by Simon Mansfield
Sydney, Australia (SPX) Apr 23, 2025
Recent innovations in solar thermoelectric generator (STEG) technology have significantly advanced the ability to convert sunlight into electricity, opening up promising applications in areas such as wearable devices, the Internet of Things, and personalized climate control. Central to these developments is the strategic refinement of thermoelectric materials, device architecture, and heat management techniques.
Among the array of materials explored, photothermal substances have emerged as particularly promising for facilitating the temperature differentials critical to efficient power generation. These materials include carbon-based compounds, metal oxides, polymers, and substances capable of phase transitions. Now, researchers from Soochow University have pushed the boundaries further by introducing a new class of organic radical photothermal materials.
The team engineered a novel charge-transfer (CT) cocrystal composed of coronene (COR) and the electron acceptor 2,6-dibromonaphthalene-1,4,5,8-tetracarboxylic dianhydride (Br2NDA). This compound, termed CBC, demonstrated exceptional photothermal conversion efficiency (PCE) of 67.2% when subjected to 808 nm light at 0.367 W/cm2. This achievement marks a significant milestone in the quest for high-performance photothermal materials.
The synthesis process utilized a simple solution-based self-assembly method, yielding crystalline microrods with distinct needle-like morphology. Advanced characterization methods confirmed the material’s structure and functionality. X-ray diffraction (XRD), selected area electron diffraction (SAED), UV-Vis spectroscopy, photoluminescence (PL), Fourier-transform infrared spectroscopy (FT-IR), and solid-state nuclear magnetic resonance (NMR) revealed strong CT interactions and a broad light absorption range of 350 to 1100 nm. These features were accompanied by near-total photoluminescence quenching and evidence of unpaired electrons via electron spin resonance (ESR), supporting the material’s CT behavior in its ground state.
Thermogravimetric analysis (TGA) validated the CBC cocrystal’s thermal robustness. Under 808 nm laser exposure, the cocrystal swiftly reached 86oC, with a calculated PCE that outperforms many organic photothermal materials to date. Its thermal stability and performance consistency were preserved across multiple irradiation cycles. Under simulated solar irradiation (2 suns), CBC achieved a temperature of 64oC, with results showing a clear linear correlation between heat generation and light intensity.
Building on this foundation, the research team embedded the cocrystal into a transparent resin, creating a photothermal ink. This was applied to a thermoelectric generator (TEG), yielding a high-performance STEG. When tested under 2 sun irradiation, the modified TEG attained a surface temperature of 70.3oC and an output voltage of 209 mV, representing a 375% gain over the uncoated TEG. The device exhibited strong durability, with stable electrical output over multiple thermal cycles and across different lighting conditions.
In a further demonstration of its versatility, the CBC-TEG system showed sensitivity to near-infrared (NIR) light, allowing it to function as a medium for wireless data transmission. By adjusting the laser’s intensity and duration, researchers successfully transmitted Morse code signals, illustrating the platform’s potential in secure communications and wearable tech applications.
This study not only introduces an efficient method for developing photothermal cocrystals but also charts a course for integrating these materials into multifunctional solar-thermoelectric platforms. The results signal new opportunities in sustainable energy conversion and smart communication technologies, with broad implications for research and industry alike.
Research Report:Radical-Activable Charge-Transfer Cocrystals for Solar Thermoelectric Generator toward Information Conversion
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