Clarification of electronic and thermal transport properties of Pb-, Ag-, and Cu-doped p-type Bi_0.52Sb_1.48Te₃

The feasibility of using Bi₂Te₃-based alloys in low-grade heat thermoelectric power generation has been intensively investigated via a substitutional doping approach over the last decade. However, the comprehensive and quantitative understanding of the electronic and thermal transport parameters of doped Bi₂Te₃-based alloys including their carrier concentration (n_c), carrier mobility (μ_Hall), density of state (DOS) effective mass (m_d^∗), and electronic (κ_ele), lattice (κ_lat), and bipolar thermal (κ_bp) conductivities is still elusive. The understanding of these parameters is a prerequisite for designing the modules for real-time applications. In this study, we investigated the effect of Pb, Ag, and Cu doping on the thermoelectric transport parameters of p-type Bi_0.52Sb_1.48Te₃ (BST) both theoretically and experimentally. The thermoelectric transport properties of BST and their temperature dependences could be systematically tuned in a low-temperature range by controlled doping of Pb, Ag, and Cu mainly because of the increased concentration of the majority hole carriers. In addition, a zT value of 1 could be obtained over the wide temperature range of 300–400 K by optimizing the doping elements and contents because of the synergetic effect of the suppression of bipolar conduction at higher temperatures and the gradual increase in m_d^∗ with the doping content at n_c < 10²⁰ cm⁻³.