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 Bi 2 Te 3 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 (00 l ) 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.