Heat-sink-free solar-driven thermoelectric device for micro energy scavenging

Harvesting energy from nature, such as mechanical energy, thermal energy, and biomass energy, has become an effective way to supply power for self-driven sensing and Internet of Things (IoT) applications. Among that, solar-driven thermoelectric (STE) device takes advantage of all-solid-state energy conversion, such as no noise, easy access, and free of wear, exhibiting great potential. Here, we propose a solar-driven thermoelectric device for harvesting solar energy, based on Micro Electromechanical System (MEMS) technology. Specifically, the optimization of solar absorptances of structural layers significantly improved the photo-thermo-electric conversion performance. Furthermore, the electrical output strongly depends on temperature difference dominated by the absorptance difference. Therefore, the reported device can be free of traditional heat sink, which greatly simplifies its structure and expands the working conditions, especially in microdevices. Particularly, a continuous output voltage of 0.34 V/cm2 is achieved with concentrated solar radiation, demonstrating its potential under no heat sink conditions. Besides, a fast response (4.2 ms under 660 nm laser) is achieved benefitting from the micron-size solar absorber, showing its significance in sensing applications. Finally, the proposed STE device is utilized to harvest outdoor solar energy, displaying promising potential in solar energy harvesting devices and providing an insightful perspective for thermoelectric applications.