Metamaterial thermoelectric conversion and nonradiative cooling (Invited Paper)

To increase the efficiency of energy harvesting, technologies that can utilize weak thermal energies existing in environments are in demand; however, conventional technologies fail to realize this objective because energy accumulation does not occur in them. Herein we propose a metamaterial for energy harvesting by which thermal energy can be accumulated from the surrounding environment and can be converted into electricity. Metamaterials are artificial thin materials that achieve optical thickness through thin geometrical structure. This feature of metamaterials results in unprecedented benefits for enhancing the performance of optoelectronic devices. In this study, we report that this metamaterial feature facilitates photo-thermoelectric conversion by enabling the accumulation of thermal energy and effective heat conduction. For example, a metamaterial-attached thermoelectric device placed in an environment with uniform thermal radiation generates an output voltage by gathering the thermal energy existing in the environment and creating an additional thermal gradient across the thermoelectric element.