International Ukrainian-Polish Agreement

“Evolution of thermoelectric properties of TlBX2 based materials under the size restrictions and doping”

(principal investigator - Candidate of Sciences in Physical and Mathematical Sciences, Tetyana Babuka)

Duration of the project: August 2020 – December 2020

Purpose: development of an adequate theoretical model for explaining the evolution of thermoelectric properties under the transition from bulk crystals TlBX2 to nanolayered structures and due to various deviations from ideality. The obtained results will be the basis for optimization of the growth technology and doping of TlBX2 structures suitable for the creation of thermoelectric energy converters.

Result: single crystals of the TlBX2 family with different structural topologies were grown by the Bridgman-Stockbarger method and detailed analysis of the structural characteristics and chemical composition were performed. Based on the first principle approaches with different approximations (DFT/PBE-D, DFT/LDA-D + U) the study of energy band spectra, total and partial densities of states, optical properties, Mulliken charges, elastic modules, phonon spectra and densities of phonon states in pure TlBX2 crystals and with a deviation from stoichiometry, as well as the effect of nanoscale effects on the electronic properties of the TlInS2 crystal were performed.