Double-layered phase change materials featuring high photothermal conversion for stable thermoelectric power generation

Organic solid-liquid phase change materials have attracted great attention in the field of photothermal conversion and energy storage due to their advantages such as high latent heat, low subcooling, stable chemical properties, and constant temperature during the phase change process. However, preparing organic composite phase change materials (CPCMs) with multiple desirable properties such as good shape stability, high thermal conductivity, high enthalpy, and excellent photothermal conversion efficiency, remains a challenge. Herein, using a rapid melt blending of expanded graphite (EG) into lauric acid (LA) and cold pressing technique, we constructed double-layered and shape-stabilized D-LA/EG composites. The upper layer consists of 20 wt% EG and 80 wt% LA, while the lower layer 6 wt% EG and 94 wt% LA. It was found that the prepared D-LA/EG exhibited good shape stability, high thermal conductivity, high enthalpy, and excellent photothermal conversion efficiency. More interestingly, when applied as a heat source for an all-solid-state thermoelectric generator in a photo-thermal-electric conversion system, a stable output voltage of 315 mV is generated after the light is ceased, which is attributed to the release of the heat stored in the CPCMs. This work provides a simple and economical strategy to synthesize and balance the above four properties CPCMs, which has potential applications in photo-thermal-electric conversion and solar energy utilization. •The synthetic methods of CPCMs are facile and economical.•The D-LA/EG sample exhibits high enthalpy value and thermal conductivity.•The D-LA/EG sample shows excellent photothermal conversion efficiency of 98.6%.•A stable output voltage (315 mV) is achieved in photo-thermal-electric system.