First-Principles Study on Thermoelectric Properties of Bi _2 O _2 Se

Compared with traditional thermoelectric (TE) materials, bismuth oxyselenide (Bi _2 O _2 Se) consists of nontoxic and lower-cost elements and has better chemical and thermal stability. The highest ZT value of Bi _2 O _2 Se ever obtained experimentally was recently reported at 0.69. To further improve its TE performance, the electron and phonon transport properties of intrinsic n -type Bi _2 O _2 Se are evaluated by first-principles calculations. Due to the density of states at the conduction band minimum being too small resulting in a low intrinsic carrier concentration, the reported TE properties of Bi _2 O _2 Se are not ideal. The TE parameters we calculated are in good agreement with the experimental values. The average optimal ZT values at 800 K for the p -type and n -type Bi _2 O _2 Se are 1.83 and 1.81, respectively, indicating that Bi _2 O _2 Se is a promising TE material. It is an innovative approach to improve the TE performance by regulating the vacancy defects in Bi _2 O _2 Se, which could achieve the cooperative optimization of electrons and phonons through the energy filtering effect and enhanced phonon scattering. Our results could provide a theoretical basis for further improving the TE properties of Bi _2 O _2 Se in experiments.