Study of the Thermoelectric Properties of Lead Selenide Doped with Boron, Gallium, Indium, or Thallium

Abstract

Group IIIA elements (B, Ga, In, and Tl) have been doped into PbSe for enhancement of thermoelectric properties. The electrical conductivity, Seebeck coefficient, and thermal conductivity were systematically studied. Room-temperature Hall measurements showed an effective increase in the electron concentration upon both Ga and In doping and the hole concentration upon Tl doping to ~7 × 10(19) cm(-3). No resonant doping phenomenon was observed when PbSe was doped with B, Ga, or In. The highest room-temperature power factor ~2.5 × 10(-3) W m(-1) K(-2) was obtained for PbSe doped with 2 atom % B. However, the power factor in B-doped samples decreased with increasing temperature, opposite to the trend for the other dopants. A figure of merit (ZT) of ~1.2 at ~873 K was achieved in PbSe doped with 0.5 atom % Ga or In. With Tl doping, modification of the band structure around the Fermi level helped to increase the Seebeck coefficient, and the lattice thermal conductivity decreased, probably as a result of effective phonon scattering by both the heavy Tl(3+) ions and the increased grain boundary density after ball milling. The highest p-type ZT value was ~1.0 at ~723 K.

High thermoelectric performance by resonant dopant indium in nanostructured SnTe

“…First-principles calculations (Table S1) indicated it is energetically favorable for In to substitute for Sn, which is consistent with the case in In-doped PbTe and PbSe. In previous work, we found In substitutes for Pb in PbTe and PbSe, which is the same with In-doped SnTe, but it is n-type doping in In x Pb 1-x Te and In x Pb 1-x Se, which is different from p-type doping by In in SnTe, as we are reporting in this work (35,36).…”

“…S1. The light-hole-heavy-hole band edge energy difference is 0.12 eV for PbTe, 0.26 eV for PbSe, and 0.35 eV for SnTe (9,29,36); thus, the heavy-hole contribution is relatively weaker for SnTe. This may be seen from the fact that there is not much difference between the predictions of VBM and those of the two-band Kane model (which ignores the heavy-hole band contribution) at room temperature for SnTe, until 10 × 10 19 cm −3 .…”

“…However, the contribution from the heavyhole band gradually increases at higher temperatures (Fig. S2) as for PbSe (9,36), helping improve the Seebeck coefficient at high temperature and suppress the bipolar effect. Although the Seebeck coefficients of bismuth-(Bi-) and Cu-doped samples agree well with the VBM model, as shown in Fig.…”

“…The carrier concentration obtained in this work is ∼2.35 × 10 20 cm −3 (filled circle). Unlike PbTe and PbSe (7,9,36,39,40), the Seebeck coefficient of SnTe shows abnormal variation with increasing carrier concentration, which was qualitatively explained previously by two parabolic band models (27) and density functional theory (DFT) calculations (31). The valence band model (VBM), which takes into account the nonparabolicity of the light-hole band (solid line), provides a quantitative fit to all the Seebeck coefficient data, except for those of In-doped samples, and thus is expected to best depict the contribution from the intrinsic band structure of SnTe (29).…”

Enhancing average ZT in pristine PbSe by over-stoichiometric Pb addition

“…2(c). Once excessive Pb was added, both Seebeck coefficient and electrical conductivity exhibited typically n-type weakly degenerate behaviors, with the near room-temperature Seebeck coefficient around −180 µV/K, being much larger than Br- 17 and In-doped 18 PbSe (around −60 µ/VK), suggesting that pristine PbSe has the fairly lower carrier concentration. Nevertheless, the enhanced power factors in nominally Pb excessive samples did not rise with temperature mainly due to the rapid drop in conductivity; consequently their high-temperature values are lower than heavily doped samples.…”