Improving the Efficiency of Thin Film Thermoelectric Generators under Constant Heat Flux by Using Substrates of Low Thermal Conductivity

Abstract

Thin film thermoelectric generators performance needs to be improved to be competitive with their bulk counterpartners. Here, a method has been proposed to enhance the efficiency of non‐conventional thin film thermoelectric generators, i.e., those with heat running parallel to the film surface, under constant heat flux configuration. This geometry offers the possibility to decouple the thermal and electronic transport via an adequate selection of the film and substrate thermal conductivities and their respective thicknesses. An analysis of those parameters and their relationships in order to reach the maximum thin film thermoelectric generators efficiency is presented in this work. It has been concluded that under well‐established conditions, the thin film thermoelectric generators efficiency is clearly increased and becomes comparable to that of the bulk thermoelectric generators under constant heat flux. This novel framework can lead to the use of devices based on compounds with high power factor regardless of their thermal conductivity.

Potential of La-Doped SrTiO3 Thin Films Grown by Metal–Organic Vapor Phase Epitaxy for Thermoelectric Applications

“…A weakness of SrTiO 3 regarding its use in thermoelectric devices is the relatively low electrical conductivity, based on the high effective mass and the resulting low charge carrier mobility, and simultaneously high thermal conductivity κ (about 5–18 Wm –1 K –1 ), which is reasoned by the centrosymmetric cubic structure that offers low effective phonon scattering centers. This weakness can be mitigated, for instance, by manufacturing superlattice heterostructures (such as Si/Ge or PbTe/PbSe 0.20 Te 0.80 superlattices), which leads to a reduction of thermal conductivity, or by decoupling the thermal and electronic transport by a suitable choice of the film and substrate thermal conductivities and respective thicknesses …”

“…This weakness can be mitigated, for instance, by manufacturing superlattice heterostructures (such as Si/Ge 15 or PbTe/PbSe 0.20 Te 0.80 16 superlattices), which leads to a reduction of thermal conductivity, 17 or by decoupling the thermal and electronic transport by a suitable choice of the film and substrate thermal conductivities and respective thicknesses. 18 In order to achieve sufficiently high electrical conductivity, films must be grown with high crystalline perfection and precisely controlled doping concentration. This requires a deposition method that allows the epitaxial growth of films with high structural quality and low defect density.…”

Wearable and flexible thin film thermoelectric module for multi-scale energy harvesting

“…Meanwhile, thin film thermoelectric devices use less amount of materials compared to bulk thermoelectric generator (TEG) and provides easy integration with integrated circuits [24,25]. The design of TEG can usually be categorized into in-plane and cross-plane structures [26]. Many works have been reported on cross-plane bismuth telluride based thin film through electrodeposition [27], screen printing [28], brush-painting [29,30] and inkjet printing [31].…”

Rapid growth of fully-inorganic flexible CaxCoO2 thin films from a ligand free aqueous precursor ink for thermoelectric applications

“…26 In fact, having a high power factor is more important than efficiency for a thin film based TEC with planar geometry, where heat flows in parallel to the film surface. 27 Therefore, the development of alternative strategies to grow high performance and mechanically flexible Ca x CoO 2 thin films in a facile, cost-effective and environment-friendly process can offer a viable solution for low power requirements of emerging portable and wearable electronics. Here, we report the rapid growth of Ca 0.35 CoO 2 thin films on sapphire and flexible mica substrates from a ligand-free aqueous TE precursor ink.…”