Reduced Bipolar Conduction in Bandgap-Engineered n-Type Cu0.008Bi2(Te,Se)3 by Sulfur Doping

Abstract

Significant bipolar conduction of the carriers in Bi2Te3-based alloys occurs at high temperatures due to their narrow bandgaps. Therefore, at high temperatures, their Seebeck coefficients decrease, the bipolar thermal conductivities rapidly increase, and the thermoelectric figure of merit, zT, rapidly decreases. In this study, band modification of n-type Cu0.008Bi2(Te,Se)3 alloys by sulfur (S) doping, which could widen the bandgap, is investigated regarding carrier transport properties and bipolar thermal conductivity. The increase in bandgap by S doping is demonstrated by the Goldsmid–Sharp estimation. The bipolar conduction reduction is shown in the carrier transport characteristics and thermal conductivity. In addition, S doping induces an additional point-defect scattering of phonons, which decreases the lattice thermal conductivity. Thus, the total thermal conductivity of the S-doped sample is reduced. Despite the reduced power factor due to the unfavorable change in the conduction band, zT at high temperatures is increased by S doping with simultaneous reductions in bipolar and lattice thermal conductivity.

Enhancement in thermoelectric performance of hydrothermally synthesized Ca and Sb co-doped Bi2Te3 nanostructures

“…A high ZT of ∼1.1 at 323 K was reported with the incorporation of Potassium and Tellurium in Bi 2 Te 3 [39]. Due to the reduction in bipolar conduction in Cu 0.008 Bi 2 (Se, Te) 3 with sulfur doping, a maximum ZT of ∼0.8 at 400 K was reported [40]. The multiscale architecture-engineered Cu 2-x S has been prepared by the wet chemical method.…”

Synergistic effect of Zn doping on thermoelectric properties to realize a high figure-of-merit and conversion efficiency in Bi2−xZnxTe3 based thermoelectric generators

“…Several reports are published in reference to the zT enhancement in polycrystalline Bi 2 Te 3 by generating extrinsic point defects via doping foreign atoms. [19][20][21][22] Besides, introducing high order dimensional defects like grain boundaries and nanoinclusions, nanostructuring in the material also shows an impressive improvement in the thermoelectric performance due to low energy electron filtering and enhanced phonon scattering. 23,24 Tang et al reported an enhanced zT value of 1.4 at 400 K in p-type Zn x Bi 0.46 Sb 1.54 Te 3+x alloys, attributed to the mixed effect of defect complexity in nanostructuring.…”