Energy harvesting is a diverse field encompassing many technologies that involve a process that captures small amounts of energy that would otherwise be lost as heat, light, sound, vibration, or movement. A thermoelectric generator (TEG) is a device that converts waste heat energy — such as solar energy, geothermal energy, and body heat — into additional electrical power.
There has been a great increase in the study of wearable thermoelectric generators using the temperature difference between body heat and the surrounding environment. One of the main drawbacks of wearable TEG techniques driven by body heat is that such temperature difference is only 1 to about 4 °C, and this has hindered further commercialization.
This issue of low temperature difference faced by conventional wearable TEGs was solved in this work by introducing a local solar absorber on a polymide PI substrate. The solar absorber is a five-period Ti/MgF2 superlattice in which the structure and thickness of each layer was designed for optimal absorption of sunlight. This has increased the temperature difference as high as 20.9 °C, which is the highest value of all wearable TEGs reported to date.
This new device is based on a temperature difference between the hot and cold sides. The wearable solar thermoelectric generator is expected to improve the efficiency by raising the temperature difference.
The noble wearable solar thermoelectric generator (W-STEG) was designed by integrating flexible BiTe-based TE legs and sub-micron-thick solar absorbers on the PI substrate. The TE legs were prepared by dispenser printing with an ink consisting of mechanically alloyed BiTe-based powders and an Sb2Te3-based sintering additive dispersed in glycerol. A W-STEG comprising 10 pairs of p-n legs has an open-circuit voltage of 55.15 mV, and an output power of 4.44 μW when exposed to sunlight.