Doping effects on the electronic structures of Bi2Te3 and thermoelectric property

The electronic structures of n- and p- Bi₂Te₃ were clarified using the molecular orbital method of Discrete Variational Xα setting two kinds of cluster such as Bi₇Te₆ and Bi₆Te₇. The present computational study was focused on the changes of electronic structures by doping another atom to the original bismuth telluride. The computational results revealed bonding strength between atoms and contour map of electron density. The atoms of Bi and Sb possessing 6p or 5p electrons are polarized to be more positive than their formal charges when doping (original Bi₂Te₃ in the case of Bi), meanwhile Ag and Cu turned to be negative. The gaps between the occupied and unoccupied levels became smaller by doping the atoms such as Ag and Cu leading to a lower electrical resistivity. Furthermore, bond strength between the center-Bi and Te in the cluster 1 (C-1) enhanced due to doping Ag or Cu as well as that of the center-Te and Bi in the cluster 2 (C-2) did. We elucidated the experimental data including electrical resistivity and Seebeck coefficient associating with the calculated electronic structures