Modifying carbon fiber fabric for flexible thermoelectric energy conversion

Fibrous conductive materials, typically, carbon fiber fabric (CFF), with warp and weft weaved carbon-fiber (CF) structure, is one of the most desirable candidates for wearable electronics by playing the role as smart devices and sensors. However, CFF suffers from extremely low mobility and Seebeck coefficient, and has rarely been considered as a potential thermoelectric material. Here, a flexible and high-strength thermoelectric material comprising ordered Bi₂Te₃ crystals anchored on CF networks is reported, where there is a crystallographic relationship exists between the Bi₂Te₃ [0 0 1] orientation and CF axis. This material, has a power factor enhanced by 2 orders of magnitude, a fourfold tensile strength compared with CFF, and the highest flexibility figure of merit ever reported. The origin of the excellent mechanical properties and the thermoelectric performance of the Bi₂Te₃/CFF material is attributed, by experimental evidence, to its crystal orientation, interface, cross-linked core–shell structure. Our results provide insight into the design and fabrication of high-strength flexible thermoelectric materials.