Simultaneous Regulation of Electrical and Thermal Transport Properties of N-Type Bi₂Te₃ via Adding Excessive Te Followed by Se Doping

Thermoelectric devices based on bismuth telluride-based alloys have been applied widely for several decades. Our results demonstrate that excessive Te constructs large amounts of anti-site defects TeBi’, thereby increasing the carrier concentration and suppressing the bipolar effect. Moreover, compared with the traditional dominated defects VTe” in other works, the TeBi’ induce smaller lattice distortion, thus alleviating carrier scattering and then increasing carrier mobility. Accordingly, a high ZT value of 0.78 at 125 °C is obtained in Bi2Te3 + 0.3 wt % Te. Then, Se doping at Te sites is used to reduce the lattice thermal conductivity by enhancing phonon scattering. Finally, a high ZT value of ∼1.0 at 125 °C and an average ZT value of 0.88 from 30 to 250 °C are realized on the Bi2Te2.5Se0.5 + 0.3 wt % Te sample.