Thermoelectric properties of 1 T monolayer pristine and Janus Pd dichalcogenides

Abstract

In this paper, we investigate the stability and thermoelectric properties of 1 T PdSSe, PdSTe and PdSeTe Janus structures using density functional theory (DFT). All three systems are narrow gap semiconductors with indirect bandgaps of 0.94 eV, 0.33 eV and 0.34 eV respectively. Compared to transition metal dichalcogenide (TMD) monolayers, PdS 2 and PdSe 2 are semiconductors with wider indirect bandgaps of 1.29 eV and 0.69 eV respectively. Phonon dispersion calculations demonstrate that all pristine and Janus structures are mechanically stable despite the presence of negligible negative frequencies around the Γ point in PdSTe and PdSeTe. Inspection of the lattice thermal conductivity (κ L ) shows that these structures are slightly anisotropic in the x and y directions except for PdSe 2 which shows a higher degree of anisotropy. Influenced by the values of κ L , the thermal electronic conductivity (κ e ), the electronic conductivity (σ) and the Seebeck effect (S), the figure of merit along the x (ZT xx )and y (ZT yy ) directions register the largest values in the case of electron doping for the PdSe 2 and PdSeTe 2D crystals. Interestingly, the figures of merit of the Janus structures are larger than their corresponding pristine PdX 2 (X = S, Se) structures. Once synthesized, such information is crucial for the implementation of the PdXY (Y = Se, Te) structures in industrial applications.

Strain-Induced Ultrahigh Electron Mobility and Thermoelectric Figure of Merit in Monolayer α-Te

“…Figure e shows the phonon dispersion of α-Te. The maximum phonon frequency corresponds to an energy of 23 meV, smaller than most of the 2D materials − due to the heavy atomic mass of Te, but is comparable to other low κ L systems. − The low phonon frequency renders a low Debye temperature for α-Te.…”

“…On the other hand, TMDs often have thermal conductivities, too high for good thermoelectrics. In parallel with the experimental study, theoretical calculations, typically involved with simplifications on an electronic band structure and a scattering rate, have been carried out to explore the TE promise of many 2D materials including MX 2 (M = Mo, W; X = S, Se), − MCO 2 (M = Ti, Zr, Hf), TiS 2 , ZrS 2 , TiS 3 , black phosphorene, PdXY (X, Y = S, Se, Te), , and Bi 2 Te 2 X (X = S, Se, Te), to name a few. The results of these calculations do not yield ZT values above unity due to a low power factor and/or high thermal conductivity.…”

Modulating via External Electric Field an Electronic Band Gaps in 2D 1T-PdS2 monolayer

“…Nonetheless, Pd pristine was not given much consideration, in particular PdS2 monolayer. We have only considered 1T PdS2 structure because of, very recently published work showing that, in the nonappearance of the spin-orbit coupling (SOC), PdS2 is semiconductor with significant bandgap [6]. The literature has conveyed various materials properties of layered PdS2 monolayer on the photonic and photoelectric fields, i.e., Wang et al, estimated the hole carrier mobility of PdS2 monolayer is ~ 339 cm 2 V -1 s -1 in the X-Dir in year of 2015 [7].…”

Strain effects on the structural, electronic, optical and thermoelectric properties of Si2SeS monolayer with puckered honeycomb structure: A first‐principles study

“…Furthermore, it is observed that Figure of merit (ZT) can be enhanced in the Janus PtSSe monolayer under compressive strain [14]. In addition, the Figure of merit in Janus Pd‐dichalcogenides structures have been found larger than their corresponding pristine PdX 2 (X = S, Se) monolayers using density functional theory [15]. Besides, Hoat et al [16] have been found that the n‐type doping can be more favorable for the high‐thermoelectric performance of the HfSSe Janus monolayer.…”