Enhanced thermoelectric properties of Bi2O2Se ceramics by Bi deficiencies

The electronic structure and the thermoelectric properties of Bi2-xO2Se (x = 0, 1/4, 1/8, 1/16, 1/32, 1/36, 1/54 and 1/64) are studied by the first principles and the semiclassical BoltzTraP theory. It is found that the energy band gaps increase with increasing x. The calculated total density of states (TDOS) near the Fermi level and bandwidth are influenced by the applied defect. The S values of Bi2-xO2Se are much larger than Bi2O2Se at the same n, due to the much larger TDOS of Bi2-xO2Se. sigma/ of p-type Bi2-xO2Se are larger than that of the n-type ones, due to the larger TDOS on the top of the valence band (VB). (0)of p-type doping is higher than that of n-type doping. Z(e)T can be increased by Bi deficiency.