MEMS thermoelectric power chip for large scale thermal energy harvesting

Abstract

The fabrication of a micro/nano-scale thermoelectric module is very challenging. In this paper, a reliableand efficient hybrid fabrication method for ultrathin thermoelectric devices based on the non-contact exposing, photoresist melting and microfabrication technology is presented. The total thickness of the thermoelectric module is about 1 μm. Experimental results indicate that ultrathin thermoelectric device works stable and reliable, and demonstrate that the method presented is suitable for fabrication of thinner and higher integrality devices beyond TE devices in the micro-nanoscale range. The peak output power density is 0.29 W/m2 and 2.9×105 W/m3. The present research can provide a useful guide for the design of a micro/nano-scale thermoelectric device in the near future. Additionally, we have demonstrated a novel energy utilization that thermoelectric generation (TEG) device can achieve self-powering by radiative cooling (RC) continuously. An ultrathin TEG with a multilayer thermal emitter was fabricated to convert the heat from the environment into electricity directly by using radiative cooling. The TEG device was consisted of more than 46,000 P-N modules in series, and each two TE modules were connected by air bridge. Thermal emitter had 80.8% emissivity in the atmospheric window (8–13 μm). Besides, maximum temperature drop of 4 K was achieved. With zero energy input, the MEMS chip output voltage of the TEG-RC reached up to 0.5 mV, and the TEG-RC exhibited a continuous average 0.18 mV output for 24 h. Extreme temperature gradients were surprisingly formed in cross section of 1.5 μm thick for micro/nano film materials. In order to improve the thermoelectric efficiency, the crossplane thermal conductivities of nano-constructed Sb2Te3/(Cu, Ag, Au, Pt) thermoelectric multilayer thin films have been measured using time-domain thermo reflectance method. The interface morphology features of multilayer thin film samples were characterized by using scanning and transmission electron microscopes. The effects of interface microstructure on the cross-plane thermal conductivities of the multilayer thin films have been extensively examined and the thermal transfer mechanism has been explored. The results indicated that electron–phonon coupling occurred at the semiconductor/metal interface that strongly affected the cross-plane thermal conductivity. This work presents both experimental and theoretical understanding of the thermal transport properties of Sb2Te3/metal multilayer thin film junctions with important implications for exploring a novel approach to improving the thermoelectric conversion efficiency.