A Thermoelectric (TE) generator is expected to play an important role in the operation of tiny-watt capable wireless power supply devices by converting the waste heat energy into electrical energy. This work is the demonstration of planar cavity-free multi-stage n-type unileg- and bileg Si-nanowire (Si-NW) TE generators. The result shows that the output power of the multi-stage bileg-TE generator increases linearly with increasing the stage number, whereas the rate of increase of the multi-stage unileg-TE generator power output tends to decrease as the stage number increases. Although the power of the multi-stage bileg-TE generator fabricated in this work was smaller than that of the multi-stage unileg-TE generator due to the large internal resistance of p-type elements, however, the improved linearity of the bileg-TE generator than the unileg-TE generator indicates the potential advantage of the multi-stage bileg-TE generator for the large-scale integration.

The performance of a thermoelectric (TE) generator consisting of Germanium-tin (GeSn) wire has been experimentally found to be higher than that of a TE generator fabricated by Silicone (Si) wire. The TE generators were developed in a cavity-free architecture, where the wires are directly placed on the substrate without forming a cavity space underneath. In the Cavity-free structure, the heat current flows perpendicularly to the substrate and the TE generator is driven by a steep temperature gradient established around the heater inlet. With an identical patterning design, the TE performance of both generators was characterized by varying lengths. The maximum Seebeck coefficient of the generator consisting of GeSn is -277 μV/K and for the Si is -97 μV/K. The GeSn-TE generator has achieved high power factor of 31 μW∙K-2 ∙cm-1 than the Si-TE generator of 12 μW∙K-2 ∙cm-1. The maximum areal power density of the GeSn-TE generator is intrinsically higher than that of the Si-TE generator by approximately 2.5 to 6 times considering the wire thickness difference. The obtained results prefer the superiority of the GeSn-TE generator over the Si-TE generator.