D-Mannitol/Graphene Phase-Change Composites with Structured Conformation and Thermal Pathways Allow Durable Solar-Thermal-Electric Conversion and Electricity Output.

Abstract

Durable electricity generation from a phase-change material (PCM)-assisted solar thermoelectric generator (STEG) through photo-thermal-electric conversion is a promising way to take advantage of the clean solar energy. However, due to the deficient and mismatched thermal charging and discharging rates in the PCMs, the previous PCM-supported STEGs usually exhibit inefficient solar-thermal-electric conversion (<1%) and limited electricity output. In this work, we report a structured D-mannitol/graphene phase-change composite fabricated by a radial ice-template assembly and infiltration strategy, in which radially aligned graphene nanoplates are bridged by graphitized polyimide that offers multidirectional and interlaced thermal highways for rapid thermal charging, while the sample conformation is further regulated by the ice-template mold, promising the optimal charging and discharging balance in the PCM. After being integrated with a solar concentrator and a thermoelectric device, this powerful STEG outputs tremendous power density, with the solar-thermal-electric conversion approaching 2.40%. The plenteous electricity supply is demonstrated to reliably charge a mobile phone under normal sunlight. This elaborate STEG design opens up opportunities for providing sufficient power guarantees for the self-powering of electronic devices in the wild.