High Thermoelectric Performance Achieved in Bulk Selenium with Nanostructural Building Blocks

Abstract

The inherent coupling between transport parameters poses great challenge in improving thermoelectric conversion performance, yet it is mitigated in material with intrinsic nanostructural building blocks by the possibility of exploiting reduced thermal conductivity and enhanced Seebeck coefficient due to strong electronic and thermal anisotropy. By applying firstprinciples methods combined with Boltzmann transport theory, we report that high thermoelectric performance can be achieved in trigonal and rhombohedral selenium due to its low-dimensional electronic transport and phonon confined features. More specifically, despite atomic chain direction showing relatively large lattice thermal conductivity, its preferable electrical conductivity (σ) and Seebeck coefficient overwhelm the adverse effects, and a large σ/κ ratio for potentially high ZT can be realized in trigonal selenium. On the other hand, benefiting from the delocalized inter-ring bonding nature and impeded thermal transportation, the electron crystal liked electronic performance and ultralow thermal conductivity in turn favor high thermoelectricity of molecular crystal rhombohedral selenium. This work not only confirms the subtle role of nanostructural building blocks in modulating the transport of the electron and phonon in anisotropic crystal structure, but also provides a strategy of searching bulk material that is promising for high performance thermoelectrics.

Remarkable Thermoelectric Performance in K2CdPb Crystals with 1D Building Blocks via Structure Particularity and Bond Heterogeneity

“…17 Such behavior is different from that of trigonal selenium, whose appreciable electrical conductivity can be attributed to the delocalized lone-pair electrons of Se atoms in the 1D atomic chain. 33 Due to the inhomogeneous bonding and special atomic configuration, the K 2 CdPb system will exhibit a large phonon anharmonicity and thus a low lattice thermal conductivity. In addition, the presence of rattling K atoms would enable high phonon−phonon scattering rates, which could serve as an example to study the synergistic effect of phonon scattering on the thermoelectric performance of low-dimensional bulk materials.…”

“…In addition, ionic-like bonding interactions between the K + cation and CdX 2– anion ensures substantial electrical transport, which will overcome the disadvantage of poor electronic properties along the interchain direction . Such behavior is different from that of trigonal selenium, whose appreciable electrical conductivity can be attributed to the delocalized lone-pair electrons of Se atoms in the 1D atomic chain . Due to the inhomogeneous bonding and special atomic configuration, the K 2 CdPb system will exhibit a large phonon anharmonicity and thus a low lattice thermal conductivity.…”

Recent Advances in the Nanomaterials, Design, Fabrication Approaches of Thermoelectric Nanogenerators for Various Applications

“…Like tellurium (Section 2.1.1), selenium (Se) is a large and multivalent chalcogen with a high Seebeck coefficient but high thermal conductivity. [ 66 ] However, selenium is not as commonly used as tellurium‐based materials in commercial TENG applications, likely due to selenium‐based TE materials exhibiting poorer TE properties than tellurium‐based materials [ 67 ] because of selenium's smaller size. However, there has been a recent resurgence in studying selenium as a replacement for tellurium because of its 10‐times‐higher abundance, lighter weight, lower cost, and lower toxicity.…”

“…[ 69 ] 2D selenium is particularly promising as a TE material, owing to its anisotropic crystal structure, high Seebeck coefficient, low thermal conductivity and high electrical conductivity. [ 66 ] However, selenium is most commonly alloyed with metals [ 70,71 ] and other materials for TE applications. [ 72,73 ] Various common selenide‐based TE materials are discussed.…”