Wearable solar thermoelectric generator driven by unprecedentedly high temperature difference

Converting body heat into electricity using flexible thermoelectric generators can be useful for self-powered wearable electronic devices. However, the temperature difference that can be obtained by body heat is insufficient, which limits its practical applications. In this study, we present a wearable solar thermoelectric generator driven by a significantly high temperature difference created by introducing a local solar absorber and thermoelectric legs on a polyimide 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. The thermoelectric 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. Thermoelectric p- and n-type legs have electrical conductivities of similar to 25,000 S m(-1) with Seebeck coefficients of 166.37 and - 116.38 mu V K-1, respectively. When exposed to sunlight, a wearable solar thermoelectric generator comprising 10 pairs of p-n legs has an open-circuit voltage of 55.15 mV and an output power of 4.44 mu W. The temperature difference is as high as 20.9 degrees C, which is much higher than the typical temperature differences of 1.5-4.1 degrees C of wearable thermoelectric generators driven by body heat. The wearable solar thermoelectric generators have been demonstrated on various surfaces exposed to sunlight, such as clothes or windows.