Thermoelectric power generation enhancement of microfabricated metal-based planar thermopiles through geometrical and device structure optimizations

Abstract

Thermoelectricity converts heat energy into electricity through a simple mechanism, in which a potential difference is generated due to the temperature difference between the hot and cold contact electrodes (AT) of coupled thermoelements. There are many types of thermoelements used in developing thermoelectric generators. However, metal thermoelements offer cheaper solutions, easier fabrication processes, and can produce substantial electricity at smaller AT. The strong correlations of electrical and thermal conductivities in metal thermoelements have resulted in lower Seebeck coefficients along with reduced thermoelectric power-generating performances. Alternatively, a thermoleg cross-sectional area (A ) optimization approach may optimize these disruptive correlations and improve their powergenerating effectiveness. A sandwiched planar structure can also allow more thermopiles to be integrated without affecting the generator’s size. In this study, thermoelectric devices based on a flexible copper (Cu)-clad polyimide substrate with simpler fabrications using Cu, nickel (Ni), and cobalt (Co) metal thermoelements were explored. Planar and lateral device structures may assist in generating larger A T and output power through their longer thermoleg length (l) and larger A . Thus, for the first time, Cu thermoleg-based generators were built on planar and lateral structures, and Co was introduced and implemented in this study too. This study also investigated the roles of previously unexplored geometrical structures such as the l and thermoleg width. Hereby, a sandwiched planar Cu/Co device was optimized by increasing the thermoleg thickness (t) of Co by 3.86 times the t of Cu, and this generator showed improvement factors of 23.5 and 40.2 times than the earlier-fabricated non-optimized Cu/Co and Cu/Ni generators, respectively. Promisingly, the A optimized sandwiched planar and lateral thick film device structures were found to be very compatible and favorable for metal-based thermoelectric generators.