Bi2Te3 single crystals with high room-temperature thermoelectric performance enhanced by manipulating point defects based on first-principles calculation

摘要

Intrinsic Bi2Te3 is a representative thermoelectric (TE) material with high performance at low temperature, which enables applications for electronic cooling. However, antisite defects easily form in p-type Bi2Te3, resulting in the difficulty of further property enhancement. In this work, the formation energy of native point defects in Bi2Te3 supercells and the electronic structure of Bi2Te3 primitive unit cell were calculated using first-principles. The antisite defect Bi_Te-1 has a lower formation energy (0.68 eV) under the Te-lack condition for p-type Bi2Te3. The effects of point defects on TE properties were investigated via a series of p-type Bi2Te3-x (x = 0, 0.02, 0.04, 0.06, 0.08) single crystals prepared by the temperature gradient growth method (TGGM). Apart from the increased power factor (PF parallel to) which originates from the increased carrier concentration (n(parallel to)) and m*, the thermal conductivity (kappa(parallel to)) was also cut down by the increased point defects. Benefitting from the high PF parallel to of 4.09 mW m(-1) K-2 and the low kappa(parallel to) of 1.77 W m(-1) K-1, the highest ZT(parallel to) of 0.70 was obtained for x = 0.06 composition at 300 K, which is 30% higher than that (0.54) of the intrinsic Bi2Te3.