Preparation of flexible photo-responsive film based on novel photo-liquefiable azobenzene derivative for solar thermal fuel application

Highly efficient conversion, long-term storage and controllable release of solar energy is always a significantly scientific issue for humans. Solar thermal fuel (STF) is considered as one kind of promising strategy with close-cycled energy-storage ability resulted from the reversible chemical isomerization of photo-responsive molecular. Azobenzene and its derivatives have been widely investigated as promising candidates for STF due to the unique photo-isomerization. However, STFs based on azobenzene moiety without any pretreatment in the charging process have seldom been reported. Here, a flexible STF device is designed and fabricated by combining photo-liquefiable 1-(4-(isopentyloxy)phenyl)-2-(p-tolyl)diazene (IPDAZ) as a photothermal conversion materials and a commercial fabric cloth as a flexible template. The total energy storage density of our STF device is as high as 288 J g−1 (80 W h kg−1) which is greatly increased by the photoinduced phase transition of the IPDAZ. Besides, the flexible IPDAZ STF film possesses good toughness, solvent stability, energy-storage capacity and recyclability, which has potential application in environment-friendly STF.