High-throughput physical vapour deposition flexible thermoelectric generators

Abstract

Flexible thermoelectric generators (TEGs) can provide uninterrupted, green energy from body-heat, overcoming bulky battery configurations that limit the wearable-technologies market today. High-throughput production of flexible TEGs is currently dominated by printing techniques, limiting material choices and performance. This work investigates the compatibility of physical vapour deposition (PVD) techniques with a flexible commercial process, roll-to-roll (R2R), for thermoelectric applications. We demonstrate, on a flexible polyimide substrate, a sputtered Bi2Te3/GeTe TEG with Seebeck coefficient (S) of 140 μV/K per pair and output power (P) of 0.4 nW per pair for a 20 °C temperature difference. For the first time, thermoelectric properties of R2R sputtered Bi2Te3 films are reported and we demonstrate the ability to tune the power factor by lowering run times, lending itself to a high-speed low-cost process. To further illustrate this high-rate PVD/R2R compatibility, we fabricate a TEG using Virtual Cathode Deposition (VCD), a novel high deposition rate PVD tool, for the first time. This Bi2Te3/Bi0.5Sb1.5Te3 TEG exhibits S = 250 μV/K per pair and P = 0.2 nW per pair for a 20 °C temperature difference.

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

“…The thinner films will have fewer high-quality connections between grains (good conducting material), with potentially poorly ordered material between (which would serve as a potential barrier). In this study, the XRD measurement was not obtained because the film is too thin to obtain sufficient signal, however the room-temperature sputtered Bi-Te film is not expected to be highly crystalline which has already been observed for thicker Bi-Te films in our previous study [72]. In the thinnest, partially coated, films, the material relies on a relatively low number of percolation pathways for conduction, and the intimate, ideal, electronic connection between neighbouring grains will not be made in many cases, thus a relatively large proportion of the moving charge will need to pass through higher potential barriers.…”

“…After a complete layer is formed, gradually increases in an approximately linear fashion, as represented in Figure 5c, as would be expected for a topological insulator until such thickness as the overall resistivity reflects that of the bulk. Changes in conductivity might also be influenced by changes in the contact with the four-point probe as the topography and morphology change, or changes in carrier mobility as a function of grain size [71] and degree of crystallinity [69,72].…”

Flexible thermoelectric films formed using integrated nanocomposites with single-wall carbon nanotubes and Bi2Te3 nanoplates via solvothermal synthesis

“…To use integrated nanocomposite films practically, it is necessary to investigate the change in the thermoelectric properties under repetitive bending conditions [51][52][53][54] . Therefore, we performed bending tests by applying stress on the film with the highest power factor (SWCNT-ethanol solution of 9 mL) and on a nanoplate film with no SWC-NTs as a reference.…”

Experimental and Computational Analyses of Temperature Distributions in Slope-Type Thin-Film Thermoelectric Generators at Different Slope Angles and Evaluation of Their Thermoelectric Performance

“…Conversely, in the structure of thin-film thermoelectric generators, strip-like thermoelectric legs of p-type and n-type semiconductors are connected with thin metal electrodes and are patterned on an insulating substrate [16][17][18][19]. Moreover, thin-film thermoelectric generators can be formed on flexible substrates [20][21][22][23]. Although they cannot easily produce a large amount of output power, it is possible to install them in almost any place, including bent and narrow spaces.…”