WFU Physics Colloquium

TITLE: Low-Dimensional Chalcogenide Nanomaterials for Thermoelectric Composites

SPEAKER: Chaochao Dun

TIME: Wednesday March 22, 2017 at 2:00 PM

PLACE: Room 101 Olin Physical Laboratory

By using hydrothermal reflux methods, a series of chalcogenides nanostructures were designed. On one hand, ternary metal chalcogenide nanowires with high thermoelectric figures of merit and power factors were obtained by using Te_1-xSe_x alloys as templates. On the other hand, Bi₂Se₃ , Bi₂Te₃, Sb₂Te₃ nanoplates and their derivatives were also fabricated. After nanostructures were obtained, we further combine them with polymers such as polyvinylidene fluoride to grantee their flexibility in thermoelectric devices. Different morphology of the nanoplates can be well controlled: For example, with different supersaturation status, different growth mode of Sb₂Te₃ nanoplates can be changed from layer by layer to spiral growth with 1 nm in spiral height. Surface modification and nanoengineering is utilized, like putting metal ions in the interlayer of n-type Bi₂Se₃ by taking advantages of its interlayer gaps, or growing self-assembled metal nanoparticles (Ag or Cu) on the lateral edges of n-type Bi₂Te₃ and p-type Sb₂Te₃ nanoplates by using their active edges. Unlike in any previous studies involved in inorganic systems, the Seebeck coefficient and electrical conductivity can increase in parallel with the introduced self- assembled heterojunction architectures because of the optimized electron and phonon transport behavior. This is one of the exciting achievements we have done in our lab to potentially change the thermoelectrics field.