Boosting self-powered wearable thermoelectric generator with solar absorber and radiative cooler

The electrical output of wearable thermoelectric generators (wTEGs) has traditionally been constrained by small temperature differentials when powering microelectronics. In this study, we innovatively combine photothermal and radiative cooling mechanisms within a single wTEGs system, enabling substantial, uninterrupted power generation. Specifically, we designed a multilayer selective solar absorber (m-SSA) composed of flexible dielectric-metal stacks. This absorber demonstrates exceptional solar absorption efficiency of 93 % and significantly low thermal emissivity of 10 %. In practical outdoor conditions, it achieves a temperature increase of up to 108 °C under solar irradiation. Concurrently, we developed a flexible hierarchically porous radiative cooler (HP-RC), which reflects 96 % of solar energy and emits 97 % of thermal energy, achieving a cooling differential of up to 10 °C, even at ambient temperatures of 42 °C. Integration of the m-SSA and HP-RC with wTEGs allows for the simultaneous harvesting of heat from solar, cold space, and earth (robots or human body). This novel energy capture mechanism yielded a notable power density of 198 mW/m² for human body and 52 mW/m² for steel robots in outdoor wearable applications. This significant advancement promotes the field toward high-performance, integrated green power technologies and holds promise for next-generation wearable self-powered devices. © 2024 Elsevier Ltd.