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

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_Te1 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∥) which originates from the increased carrier concentration (n ∥) and m*, the thermal conductivity (κ ∥) was also cut down by the increased point defects. Benefitting from the high PF∥ of 4.09 mW m-1 K-2 and the low κ ∥ of 1.77 W m-1 K-1, the highest ZT ∥ 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.