Biaxial Tensile Strain-Induced Enhancement of Thermoelectric Efficiency of α-Phase Se2Te and SeTe2 Monolayers

Abstract

Thermoelectric (TE) materials can convert waste heat into electrical energy, which has attracted great interest in recent years. In this paper, the effect of biaxial-tensile strain on the electronic properties, lattice thermal conductivity, and thermoelectric performance of α-phase Se2Te and SeTe2 monolayers are calculated based on density-functional theory and the semiclassical Boltzmann theory. The calculated results show that the tensile strain reduces the bandgap because the bond length between atoms enlarges. Moreover, the tensile strain strengthens the scatting rate while it weakens the group velocity and softens the phonon model, leading to lower lattice thermal conductivity kl. Simultaneously, combined with the weakened kl, the tensile strain can also effectively modulate the electronic transport coefficients, such as the electronic conductivity, Seebeck coefficient, and electronic thermal conductivity, to greatly enhance the ZT value. In particular, the maximum n-type doping ZT under 1% and 3% strain increases up to six and five times higher than the corresponding ZT without strain for the Se2Te and SeTe2 monolayers, respectively. Our calculations indicated that the tensile strain can effectively enhance the thermoelectric efficiency of Se2Te and SeTe2 monolayers and they have great potential as TE materials.

Electronic and thermoelectric properties of semiconducting Bi2SSe2 and Bi2S2Se monolayers with high optical absorption

“…As a representative parameter of the mean free path, the x 0 values of Bi 2 SSe 2 and Bi 2 S 2 Se monolayers are 155 nm and 285 nm, respectively, which are smaller than those of stanene (2710 nm) 59 and InAs (310 nm) 38 but larger than those of SnS 2 (67.7 nm) 60 and Se 2 Te (39.7 nm). 61 These values can be used as the effective reference for size tuning.…”

Dual Substrate Effect of Silicon Substrate on Thermal Transport Characteristic of (14,14,14)‐Graphyne: Transformation from Conventional Suppressing Role to Abnormal Promoting Role

“…Generally, tensile strain enhances phonon-phonon scattering and leads to phonon softening, ultimately causing a decrease in TC. [45,46] However, for some special structures, their TCs exhibit a nonmonotonic trend with increasing tensile strain, the relevant mechanisms involve unique bond lengths, bond angles, model size effects, and the influence of isolated electron pairs. [47][48][49][50] Moreover, Chen's research indicates that the TC responses of the same material in different directions are also different, e.g., hydrogen-encapsulated GR-like borophene exhibits a nonmonotonic change in TC with tensile strain in the armchair direction, while the TC in the zigzag direction shows a monotonic trend.…”