Thermoelectric behaviour of Bi-Te films on polymer substrates DC-sputtered at room-temperature in moving web deposition

Abstract

High-throughput roll-to-roll processing could be used to scale up the manufacture of flexible thermoelectric generators. Very thin thermoelectric layers can be manufactured at high throughput speed and low cost and, most importantly, are predicted to possess better thermoelectric properties than thicker layers. Here we present a study on a series of bismuth telluride films of different thickness (few nm to 370 nm), deposited on polymer substrates at room temperature using DC magnetron sputtering. Unlike previous studies of deposition of bismuth telluride films onto heated substrates, an island-growth mode, indicated by AFM, was observed for Bi-Te films grown at room temperature. A period of growth in which the layer only partially coats the substrate, with only imperfect connections between islands, was observed. In this partially coated region, the coating exhibited an extremely high Seebeck coefficient. An energy barrier mechanism, similar to the interface effect in nanomaterials, is proposed to explain this phenomenon, along with a possible quantum confinement effect. We found that a thinner Bi-Te film could generate a greater power factor because of a quasidecoupling of Seebeck coefficient and electrical resistivity. In addition, ensuring that the

Linear Electron Beam Assisted Roll-to-Roll in-Vacuum Flexographic Patterning for Flexible Thermoelectric Generators

“…The authors. Tao et al and Morgan et al demonstrated considerable progress in other publications to optimize chalcogenide-based devices on the lab scale [5][6][7]14]. Significant research and development are still required for industrialization.…”

“…Webs of flexible substrates are wound at high speeds, e.g., 10-500 m min −1 from one roll, through processing chambers, back onto another roll. Multiple layers of a device can be deposited in sequential deposition steps within a single pass of the R2R [4][5][6][7][8]. Physical vapour deposition (PVD) techniques, such as sputtering and thermal evaporation, offer high-quality and tuneable thin films and recently demonstrated promising R2R compatibility for high-throughput manufacturing of f-TEGs.…”

“…The effects of this Electron beam cleaning will be assessed in the form of multiple f-TEGs by subsequent deposition of thermoelectric materials by sputtering through a shadow mask. Optimisation of the particularly active thermoelectric materials of BiTe and BiSbTe or GeTe was extensively investigated within the group and through collaborators, however, with limited scalability via the use of shadow masked electrodes [5][6][7]14]. Here, we aim to successfully demonstrate the next required processing step for the realisation of continuous oil masking of the electrode to fabricate a full device architecture within a dynamic R2R system.…”

Novel Stacking Design of a Flexible Thin‐Film Thermoelectric Generator with a Metal–Insulator–Semiconductor Architecture

“…[28] Among them, only sputtering shows the most promise for scale-up manufacture of TEGs like R2R processing. [29] Hence, sputtering is employed in this study.Flexible thin-film TEGs can be assembled in both crossplane (CP-TEG) and in-plane (IP-TEG) structural designs, which allow heat flows/TE legs perpendicular and parallel, respectively, to the substrate. [30] CP-TEG has already been commercialized in bulk TEGs and some μTEGs, however, to further decrease the size to nanorange, the crossplane configuration is not practical since maintaining a large ΔT across a nanothick TE leg is an almost impossible challenge [14,31] and the power output is very poor (e.g., refs.…”

“…[28] Among them, only sputtering shows the most promise for scale-up manufacture of TEGs like R2R processing. [29] Hence, sputtering is employed in this study.…”