High-Performance Flexible Bismuth Telluride Thin Film from Solution Processed Colloidal Nanoplates

Thermoelectric generators are an environmentally friendly and reliable solid-state energy conversion technology. Flexible and low-cost thermoelectric generators are especially suited to power flexible electronics and sensors using body heat or other ambient heat sources. Bismuth telluride (Bi₂Te₃) based thermoelectric materials exhibit their best performance near room temperature making them an ideal candidate to power wearable electronics and sensors using body heat. In this report, Bi₂Te₃ thin films are deposited on a flexible polyimide substrate using low-cost and scalable manufacturing methods. The synthesized Bi₂Te₃ nanocrystals have a thickness of 35 ± 15 nm and a lateral dimension of 692 ± 186 nm. Thin films fabricated from these nanocrystals exhibit a peak power factor of 0.35 mW m⁻¹·K⁻² at 433 K, which is among the highest reported values for flexible thermoelectric films. In order to evaluate the flexibility of the thin films, static and dynamic bending tests are performed while monitoring the change in electrical resistivity. After 1000 bending cycles over a 50 mm radius of curvature, the change in electrical resistance of the film is 23%. Using Bi₂Te₃ solutions, the ability to print thermoelectric thin films with an aerosol jet printer is demonstrated, highlighting the potential of additive manufacturing techniques for fabricating flexible thermoelectric generators.