School Of Basic And Applied Sciences

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Author: search.filters.author.Jakhar, MukeshSubject: search.filters.subject.density functional theory

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    Janus ?-PdXY (X/Y = S, Se, Te) materials with high anisotropic thermoelectric performance
    (Royal Society of Chemistry, 2023-02-21T00:00:00) Jakhar, Mukesh; Sharma, Raman; Kumar, Ashok
    Two-dimensional (2D) materials have garnered considerable attention as emerging thermoelectric (TE) materials owing to their unique density of states (DOS) near the Fermi level. We investigate the TE performance of Janus ?-PdXY (X/Y = S, Se, Te) monolayer materials as a function of carrier concentration and temperature in the mid-range from 300 to 800 K by combining density functional theory (DFT) and semi-classical Boltzmann transport theory. The phonon dispersion spectra and AIMD simulations confirm their thermal and dynamic stability. The transport calculation results reveal the highly anisotropic TE performance of both n and p-type Janus ?-PdXY monolayers. Meanwhile, the coexistence of low phonon group velocity and a converged scattering rate leads to a lower lattice thermal conductivity (Kl) of 0.80 W mK?1, 0.94 W mK?1, and 0.77 W mK?1 along the y-direction for these Janus materials, while the high TE power factor is attributed to the high Seebeck coefficient (S) and electrical conductivity, which are due to the degenerate top valence bands of these Janus monolayers. The combination of lower Kl and a high-power factor at 300 K (800 K) leads to an optimal figure of merit (ZT) of 0.68 (2.21), 0.86 (4.09) and 0.68 (3.63) for p-type Janus PdSSe, PdSeTe and PdSTe monolayers, respectively. To evaluate rational electron transport properties, the effects of acoustic phonon scattering (?ac), impurity scattering (?imp), and polarized phonon scattering (?polar) are included in the temperature-dependent electron relaxation time. These findings indicated that the Janus ?-PdXY monolayers are promising candidates for TE conversion devices. � 2023 The Royal Society of Chemistry.
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    Stability, optoelectronic and thermal properties of two-dimensional Janus ?-Te2S
    (IOP Publishing Ltd, 2022-02-14T00:00:00) Singh, Jaspreet; Jakhar, Mukesh; Kumar, Ashok
    Motivated by recent progress in the two-dimensional (2D) materials of group VI elements and their experimental fabrication, we have investigated the stability, optoelectronic and thermal properties of Janus ?-Te2S monolayer using first-principles calculations. The phonon dispersion and MD simulations confirm its dynamical and thermal stability. The moderate band gap ( 1/41.5 eV), ultrahigh carrier mobility ( 1/4103 cm2 V-1 s-1), small exciton binding energy (0.26 eV), broad optical absorption range and charge carrier separation ability due to potential difference ( "V = 1.07 eV) on two surfaces of Janus ?-Te2S monolayer makes it a promising candidate for solar energy conversion. We propose various type-II heterostructures consisting of Janus ?-Te2S and other transition metal dichalcogenides for solar cell applications. The calculated power conversion efficiencies of the proposed heterostructures, i.e. ?-Te2S/T-PdS2, ?-Te2S/BP and ?-Te2S/H-MoS2 are 1/421%, 1/419% and 18%, respectively. Also, the ultralow value of lattice thermal conductivity (1.16 W m-1 K-1) of Janus ?-Te2S makes it a promising material for the fabrication of next-generation thermal energy conversion devices. � 2022 IOP Publishing Ltd.