Molecular Engineering of Vibronic Coupling Enables High-Temperature Solar-Thermal Conversion in an Organic Material

Solar-thermal conversion offers a direct route for harvesting solar energy, yet most organic materials reported are limited to moderate temperatures and low-temperature applications. Here, we report BTDyA, an organic material designed for high-temperature solar-thermal conversion, achieved by bridging triphenylamine donors with [1,2,5]thiadiazolo[3,4-f]benzotriazole acceptor via ethynyl linkages. BTDyA demonstrates a high molar absorption coefficient and broadband solid-state absorption, enabled it to reach a temperature as high as 330 °C under concentrated outdoor sunlight, the highest reported value for organic solar-thermal materials. Moreover, under 1064 nm laser irradiation, the temperature could be further elevated to 377 °C. The transient absorption and photoinduced Raman spectroscopies reveal that BTDyA undergoes ultrafast nonradiative decay in the excited-state, coupled with significant vibronic activation. These promote efficient conversion of photon energy into molecular vibronic energy and heat, while suppressing radiative losses and enhancing photothermal performance. The high-temperature capability of BTDyA positions it as a promising candidate for solar energy harvesting and thermal storage. These findings offer critical insights into the design principles and photothermal mechanisms of organic materials for high-temperature solar-thermal applications, paving the way for their future use in renewable energy technologies.