Harvesting waste heat with flexible Bi2Te3 thermoelectric thin film

Thermoelectric materials offer the possibility of harvesting huge amounts of waste heat, such as vehicle exhaust gases, and converting them directly into useful electricity, a process that generates power more sustainably. Flexible thermoelectrics have emerged as a technology to power wearable electronics and sensors, although coupling of thermoelectric performance and flexibility remains a big challenge. Here, we show a Bi2Te3 thin-film design that features high thermoelectric performance (room-temperature figure of merit ZT of ~1.2) and high flexibility (surviving 2,000 bending tests at an 8 mm bending radius). The favourable combination of high performance and flexibility is rooted in the textured structure of the film on the (00l) plane. The assembled flexible device from 40 pairs of thin films exhibits an outstanding output power density of 2.1 mW cm−2 at a temperature gradient of 64 K, demonstrating potential application in harvesting thermal energy from the environment or human bodies.