Energy density enhancement of scalable thermoelectric devices using a low thermal budget method with film thickness variation

Additive manufacturing has been investigated as a more time, energy, and cost-efficient method for fabricating thermoelectric generators (TEGs) compared to traditional manufacturing techniques. Early results have been promising but are held back by including 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 combination of micron and nano-sized particles, the application of mechanical pressure (20 MPa), and thickness variation (170, 240, 300 µm) – on the performance of stencil printed p-Bi_0.5Sb_1.5Te₃ (p-BST) and n-Bi₂Te_2.7Se_0.3 (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) of 0.89 and 0.5 for p-BST and n-BTS thinner (170 µm) films, 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 an LED and charge and discharge capacitor at a ∆T of 17 K, demonstrating its applicability as a self-sufficient power source.