Plastic-Deformation-Free Fabrication of Freestanding Metal Chalcogenide Ribbons for High-Performance Flexible Thermoelectric Generators.

Ductile metal chalcogenide semiconductors are intriguing candidates for sustainable, high-performing flexible thermoelectric generators (f-TEGs). Processing bulk ductile semiconductors into flexible ribbons relies heavily on plastic deformation; however, such deformation inevitably induces defects that cause detrimental carrier scattering. Furthermore, processing low-plasticity semiconductors via plastic deformation is particularly challenging, as their inherent brittleness predisposes them to fracture under stress. Herein, we develop a melt spinning strategy that avoids plastic deformation and directly enables the efficient and scalable fabrication of freestanding p-type CuAg(Te,Se,S) and n-type Ag2(Se,S) flexible ribbons even some of the chalcogenides possess low plasticity. Facilitated by the synergy of thin thickness, tuned compositions and refined microstructures, the ribbons with optimized compositions exhibit excellent flexibility. Moreover, modulating the chalcogen compositions endows the flexible ribbons with superior near-room-temperature power factors, peaking at 1618 and 879 µW m-1 K-2 for n-type Ag2Se0.8S0.2 and p-type CuAgTe0.9Se0.04S0.06, respectively. Notably, the in-plane f-TEGs assembled from highly flexible CuAg(Te,Se,S) and Ag2(Se,S) ribbons possess impressive normalized power densities that compare favorably to those of f-TEGs constructed from organic thermoelectrics or inorganic-organic composites. This work provides a useful plastic-deformation-free paradigm for fabricating freestanding metal chalcogenide ribbons with high flexibility and thermoelectric properties toward the applications in wearable electronics.