Several ternary “Janus” metal dichalcogenides such as {Mo,Zr,Pt}-SSe have emerged as candidates with significant potential for optoelectronic, piezoelectric, and thermoelectric applications. SnSSe, a natural option to explore as a thermoelectric given that its “parent” structures are SnS 2 and SnSe 2 has, however, only recently been shown to be mechanically stable. Here, we calculate the lattice thermal conductivities of the Janus SnSSe monolayer along with those of its parent dicalchogenides. The phonon frequencies of SnSSe are intermediate between those of SnSe 2 and SnS 2 ; however, its thermal conductivity is the lowest of the three and even lower than that of a random Sn[S 0.5 Se 0.5 ] 2 alloy. This can be attributed to the breakdown of inversion symmetry and manifests as a subtle effect beyond the reach of the relaxation-time approximation. Together with its low favorable power factor, its thermal conductivity confirms SnSSe as a good candidate for thermoelectric applications.

An energetic and dynamical stability analysis of five candidate structures—hexagonal, buckled hexagonal, litharge, inverted litharge, and distorted-NaCl—of the SnS monolayer is performed using density functional theory. The most stable is found to be a highly distorted-NaCl-type structure. The thermoelectric properties of this monolayer are then calculated using the density functional theory and the Boltzmann transport equation. In terms of phonon scattering, there is a sharp contrast between this monolayer and bulk materials, where normal processes are more important. The calculations reveal that the SnS monolayer has enhanced electrical performance as compared to the bulk phase. As a consequence, high figures of merit ZT∼5 and ZT∼1.36 are predicted at 600 and 300 K, respectively, for the monolayer, ∼33 times higher than the ZT of its bulk analog. Therefore, this structure is an interesting candidate for room-temperature thermoelectric applications. A comparison between the fully ab initio results and simpler models based on relaxation times for electrons and phonons highlights the efficiency of computationally inexpensive models. However, ab initio calculations are found to be very important for the prediction of thermal transport properties.

The global energy crisis demands the search for new materials for efficient thermoelectric energy conversion. Theoretical predictive modelling with experiments can expedite the global search of novel and ecoconscious thermoelectric...

Tin-based chalcogenides have a lot of potential as thermoelectric materials due to their ultralow thermal conductivity. Therefore, most reports on doped SnS focus on its power factor as the other condition for a high thermoelectric figure of merit (ZT). Here, we use the Boltzmann transport formalism to calculate both the power factor and the thermal conductivity for SnS, SnSe, and SnSxSe1−x and compare it with experimental measurements. Our theoretical model, based on a relaxation-time formalism, is in very good agreement with the reported values. We conclude that, while impurity scattering plays a major role in electron transport and, therefore, largely determines the power factor, alloy scattering is crucial for phonon transport. Specifically, alloying reduces the thermal conductivity of SnSe0.70S0.30 by a factor of ∼1.3 compared to SnSe and by a factor of ∼2 compared to SnS. This leads to ∼65% and ∼33% enhancements of ZT for p-type and n-type doping, respectively, at 800 K with respect to SnSe.

The electronic energy bands of PtSn2 are calculated using composite wave variational version of the APW method. The results show a narrowing of d‐band which indicates a weaker d‐d overlap interaction between Pt atoms. A comparative study of this band structure result with that of PtAl2 and Pt provide interesting information about d‐d interaction as a function of primary interatomic distance. From the band structure results, density of states, joint density of states, ε2(ω) spectra and the Fermi surfaces are calculated and interpreted.

Two dimensional (2D) materials are emerging candidates for thermoelectric applications because of their exceptional electronic and mechanical properties. A serious impediment to improving thermoelectric (TE) efficiency is electrical (σ) and thermal (κ) conductivity, which are related and cannot be tuned separately. In this study, we have shown that the heterostructures of Janus MoSSe and graphene have a negative correlation between electrical and thermal conductivity. It is also possible to design both p-type and n-type legs by using a pure and phosphorus-doped heterostructure. We obtained a power factor of 3410 μW m–1 K–2 for p-type and 2450 μW m–1 K–2 for n-type cases at room temperature. The lattice thermal conductivity is reduced to 13.28 W m–1 K–1 for pure and 8.36 W m–1 K–1 for the P-doped heterostructure from 17.32 W m–1 K–1 for Janus MoSSe at 300 K. A promising figure of merit is obtained for the 2D TE device made by Janus MoSSe and graphene heterostructures.

Nanostructuring is one of the well-known tools for improving the thermoelectric figure of merit, but it has limits when tuning the lattice thermal conductivity. The thermoelectric coefficients, including the lattice thermal conductivity in two-dimensional materials, can further be modified using strain engineering, which manipulates the interatomic forces and the energy levels in these systems. With this in mind, we investigate the thermoelectric properties of the SnS monolayer under uniaxial compressive and tensile strains using first-principles calculations and the Boltzmann transport equation. Analysis of the elastic constants and Poisson ratio points toward the applicability of strain only along the armchair or b direction. Systems with uniaxial compressible and tensile strains from −4% to 5% along the armchair direction are found to be dynamically stable. A high power factor of ∼1.1 W m–1 K–2, which is ∼1.8 times higher than the unstrained case, is predicted for the 1% strain case for p-type carriers. A ∼77% enhancement in the dimensionless figure of merit (ZT) for p-type carriers and ∼86% enhancement in the figure of merit for n-type carriers with respect to equilibrium is detected upon application of a minimal 1% tensile strain. An almost 3-fold increase in ZT can be achieved for 1% strain at 600 K. This enhancement in ZT renders the strained monolayer a much more promising candidate for thermoelectric applications.

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