High-energy and light-actuated phase change composite for solar energy storage and heat release

Abstract Phase change materials (PCMs) show great potential for solar thermal energy application due to the large latent heat and high efficiency. However, it is difficult to implement long-term storage because of the sensitive phase-transition to environment temperature. Here, we report a high-energy organic phase change composite (PCC) by introducing long-chain azobenzene molecule (AZO) into low-cost tetradecyl alcohol (TA) for light-regulated solar energy storage and release. The photo-switch azobenzene can install a new energy barrier and form a supercooling in liquid-phase charged PCC via molecular photo-isomerization and enhanced intermolecular interactions. Moreover, the charged PCC reveals a large latent heat of 239 J g−1 and a high power density of 594 W kg−1 with a suitable degree of supercooling (3.33–7.67 °C) for energy storage near room temperature. It is noted that the optically-controlled energy release by blue light and excellent cycling stability can be obtained. This kind of PCC is a promising candidate for smart and convenient solar energy storage application.