Thin film based thermoelectric energy conversion systems

Abstract

Up to now thermoelectric materials used in commercial energy conversion devices like infrared sensors, Peltier-coolers or thermogenerators do not take advantage of the enormous potentials provided by low-dimensional structures. The scope of this presentation is the experimental verification of the predicted increase of the thermoelectric figure of merit (FOM) ZT in low-dimensional systems above values of bulk materials. Concepts for the realization of devices using low dimensional structures based on the classical thermoelectric materials (V-VI-compounds for temperatures around 300 K and IV-VI-materials for temperatures up to 600 K, silicides for high temperature applications) were made. We will present briefly the preparation and thermoelectric properties of IV-VI and V-VI superlattice (SL) structures grown by molecular beam epitaxy as well as on Si-Ge SL structures grown by magnetron sputter epitaxy. An important part is the theoretical modeling of these new thin film devices. The results were used to determine the bests uited geometrical dimensions and to compare the calculated device performance with the experimental results. Further more, the results will be discussed with respect to the rising industrial interest in high performance thermoelectric thin and thick film devices

Thermoelectric Nanostructures: From Physical Model Systems towards Nanograined Composites

“…A superlattice structure can, however, survive the processing to a device. [ 70 ] In this unique demonstration geared towards a thermoelectric sensor application, a Bi 2 Te 3 / Bi 2 (Se,Te) 3 multilayer was transferred from a sacrifi cial BaF 2 substrate to a polyester foil, whereby the typical high-resolution X-ray diffraction superlattice pattern was only marginally affected due to the bending of the polyester foil.…”

Distributed Control to Improve Performance of Thermoelectric Coolers

“…To overcome these performance limitations, many research initiatives are currently seeking to improve the effectiveness of TECs by improving the materials used for these coolers [2]. Examples of possibilities that are being explored include skutterudites, nanotechnology, superlattices, and thin-films [3][4][5][6][7][8]. Additional research has also been devoted to improving fin-fan systems, minimizing contact resistances, and employing multistage TECs, which have already been implemented in chip-cooling applications [9][10][11][12][13][14].…”

“…The theoretical ZT limit of 6.0 is based on reducing the thermal conductivity to its minimum value by engineering the mean free path to approximate the phonon wavelength [33]. Thin-films are materials that are grown layer by layer usually by molecular beam epitaxy (MBE) [7]. The resulting material thickness is on the order of nanometers resulting in a restriction for phonons.…”

Enhancing Performance of Thermoelectric Coolers Through the Application of Distributed Control

“…To overcome these performance limitations, many research initiatives are currently seeking to improve the effectiveness of TECs by improving the materials used for these coolers [2]. Examples of possibilities that are being explored include skutterudites, superlattices, thin films, and other nanostructured materials [3]- [7]. Additional research related to chip cooling has also been devoted to improving fin-fan systems, minimizing contact resistances, and employing multistage TECs, which have already been implemented in chip-cooling applications [8]- [13].…”