Regulating Te Vacancies through Dopant Balancing via Excess Ag Enables Rebounding Power Factor and High Thermoelectric Performance in p‐Type PbTe

Abstract

Thermoelectric properties are frequently manipulated by introducing point defects into a matrix. However, these properties often change in unfavorable directions owing to the spontaneous formation of vacancies at high temperatures. Although it is crucial to maintain high thermoelectric performance over a broad temperature range, the suppression of vacancies is challenging since their formation is thermodynamically preferred. In this study, using PbTe as a model system, it is demonstrated that a high thermoelectric dimensionless figure of merit, zT ≈ 2.1 at 723 K, can be achieved by suppressing the vacancy formation via dopant balancing. Hole-killer Te vacancies are suppressed by Ag doping because of the increased electron chemical potential. As a result, the re-dissolution of Na 2 Te above 623 K can significantly increase the hole concentration and suppress the drop in the power factor. Furthermore, point defect scattering in material systems significantly reduces lattice thermal conductivity. The synergy between defect and carrier engineering offers a pathway for achieving a high thermoelectric performance by alleviating the power factor drop and can be utilized to enhance thermoelectric properties of thermoelectric materials.

Breaking the sodium solubility limit for extraordinary thermoelectric performance in p-type PbTe

“…A similar phenomenon was also observed in a previous study. 61 Due to V Te defect annihilation, the Na solubility and doping efficiency are largely enhanced in the LISST system.…”

“…The improved Na solubility facilitates the band convergence between the light valence band (L) and secondary valence band (Σ) in PbTe. Therefore, Pb 1−y Na y Te–0.5% AgInSe 2 ( y = 0.05, 0.06) compounds possess the highest effective mass and carrier concentration compared with previous p-type PbTe-based materials 12,37,48,49,54,56,60–62 (Fig. 1b).…”

Two-dimensional layered architecture constructing energy and phonon blocks for enhancing thermoelectric performance of InSb

“…Jiang et al [29] got a decreased lattice thermal conductivity of ~10 Wm −1 K −1 in InSb via in situ introducing NiSb precipitates and more recently, Yang and co-workers [30,31] achieved a large reduction of lattice thermal conductivity in a narrow temperature range with the help of InSb-Sb eutectic structure. However, the thermoelectric performance of InSb is far inferior to the currently mid-temperature thermoelectric materials such as PbTe [32] and CoSb 3 [33], which is mainly due to its high thermal conductivity and small Seebeck coefficient. As is known, the thermal conductivity of TE materials can be largely reduced through introducing multi-scale second phases, and the electrical transport properties such as carrier mobility may also get deteriorated.…”

Significantly Enhanced Thermoelectric Performance Achieved in CuGaTe2 through Dual-Element Permutations at Cation Sites

“…Using these strategies, greatly improved thermoelectric performance has been achieved in various material series. However, till now, most state-of-the-art thermoelectric materials are narrow-gap semiconductors, such as PbTe, ,− PbSe, ,, GeTe, − SnTe, − SnSe, ,, and Bi 2 Te 3, , to name but a few. They all share the same trouble that the thermoelectric performance starts to degrade at high temperatures due to the so-called bipolar effect, i.e., electrons skip across the band gap from valence band maximum to conduction band minimum.…”