Ultrahigh thermoelectric properties of p‐type Bi_xSb_2−xTe₃ thin films with exceptional flexibility for wearable energy harvesting

Abstract Use of a flexible thermoelectric source is a feasible approach to realizing self‐powered wearable electronics and the Internet of Things. Inorganic thin films are promising candidates for fabricating flexible power supply, but obtaining high‐thermoelectric‐performance thin films remains a big challenge. In the present work, a p‐type Bi_xSb_2−xTe₃ thin film is designed with a high figure of merit of 1.11 at 393 K and exceptional flexibility (less than 5% increase in resistance after 1000 cycles of bending at a radius of ∼5 mm). The favorable comprehensive performance of the Bi_xSb_2−xTe₃ flexible thin film is due to its excellent crystallinity, optimized carrier concentration, and low elastic modulus, which have been verified by experiments and theoretical calculations. Further, a flexible device is fabricated using the prepared p‐type Bi_xSb_2−xTe₃ and n‐type Ag₂Se thin films. Consequently, an outstanding power density of ∼1028 μW cm⁻² is achieved at a temperature difference of 25 K. This work extends a novel concept to the fabrication of high‐performance flexible thin films and devices for wearable energy harvesting.