Interfacial Engineering Using Additive Manufacturing to Decouple Electrical and Thermal Conductivity for Next-Generation Thermoelectrics

Abstract

Additive manufacturing has been investigated as a more time, energy, and cost-efficient method for fabricating thermoelectric generators (TEGs). Early results have been promising but are held back by the necessary inclusion of a high-temperature, long-duration curing process to produce high-performance thermoelectric (TE) films. This work investigates the synergistic effect of four factors – a small amount of chitosan binder (0.05wt%), a heterogeneous particle size distribution, the application of mechanical pressure, and thickness variation – on the performance of p-Bi₀.₅Sb₁.₅Te₃ (p-BST) and n-Bi₂Te₂.₇Se₀.₃ (n-BTS) TE composite films. The combination of these four factors controls the micro and nanostructure of the films to decouple their electrical and thermal conductivity effectively. This resulted in figures of merit (ZTs) (0.89 and 0.5 for p-BST and n-BTS, respectively) comparable to other additive manufacturing methods despite eliminating the high-temperature, long-duration curing process. The process was also used to fabricate a 6-couple TEG device which could generate 357.6 µW with a power density of 5.0 mW/cm² at a ∆T of 40 K. The device demonstrated air stability and flexibility for 1000 cycles of bending. Finally, the device was integrated with a voltage step-up converter to power a LED and charge and discharge capacitor at a ∆T of 17 K, demonstrating its applicability as a self-sufficient power source.