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

Abstract

A stacked thermoelectric generator on a flexible polymer sheet is investigated that can utilize a low-cost high throughput roll-to-roll process, employing a metal–insulator–semiconductor structure of <100 nm thick Cu and bismuth telluride films with a ≈1 µm thick acrylate insulating coating. Thermoelectric strips can be stacked and connected in the out-of-plane direction, which significantly decreases the size required in the substrate plane and also gives rise to the opportunity for greatly extending power output by stacking thousands of layers. A smooth surface of stacked layers is confirmed due to the nature of the acrylate layer. Room-temperature sputtering can produce good quality/crystalline films, indicated by X-ray diffraction and transmission electron microscope. Both experimental and simulation results observe a small temperature gradient across the stack from the bottom heat source to the top free surface. A stacked thermoelectric generator shows comparable performance to an in-plane device, and most notably, the stacked architecture allows a higher power output without increasing the dimension of the device in the substrate plane, while the thickness is increased within only a µm range. Cyclic buckling fatigue tests suggest that the performance of stacked functional strips can be protected under deformation within the acrylate matrix.