Department Of Physics

Permanent URI for this communityhttps://kr.cup.edu.in/handle/32116/57

Browse

Subject: search.filters.subject.Two-dimensional

Search Results

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    First principles study of 2D ring-Te and its electrical contact with a topological Dirac semimetal
    (Royal Society of Chemistry, 2023-02-10T00:00:00) Singh, Jaspreet; Kumar, Ashok
    In recent years, researchers have manifested their interest in two-dimensional (2D) mono-elemental materials of group-VI elements because of their excellent optoelectronic, photovoltaic and thermoelectric properties. Despite the intensive recent research efforts, there is still a possibility of novel 2D allotropes of these elements due to their multivalency nature. Here, we have predicted a novel 2D allotrope of tellurium (ring-Te) using density functional theory. Its stability is confirmed by phonon and ab initio molecular dynamics simulations. Ring-Te has an indirect band gap of 0.69 eV (1.16 eV) at the PBE (HSE06) level of theories and undergoes an indirect-direct band gap transition under tensile strain. The higher carrier mobility of holes (?103 cm2 V?1 s?1), good UV-visible light absorption ability and low exciton binding (?0.35 eV) of ring-Te give rise to its potential applications in optoelectronic devices. Furthermore, the electrical contact of ring-Te with a topological Dirac semimetal (sq-Te) under the influence of an electric field shows that the Schottky barriers and contact types can undergo transition from p-type to n-type Schottky contact and then to ohmic contact at a higher electric field. Our study provides an insight into the physics of designing high-performance electrical coupled devices composed of 2D semiconductors and topological semimetals. � 2023 The Royal Society of Chemistry.
  • No Thumbnail Available
    Item
    Two-dimensional ?-PdX2 (X = S, Te) monolayers for efficient solar energy conversion applications
    (Royal Society of Chemistry, 2022-02-09T00:00:00) Jakhar, Mukesh; Kumar, Ashok
    The search for highly effective and environmentally safe photocatalysts for water splitting and photovoltaic solar cells is essential for renewable solar energy conversion and storage. Based on first-principle calculations, we show that novel 2D ?-PdX2 (X = S, Te) monolayer possesses excellent stability and great potential in solar energy conversion applications. Comprehensive studies show that the ?-PdS2 monolayer exhibits semiconductor characteristics with an indirect gap, suitable band alignment, efficient carrier separation, and high solar to hydrogen (STH) efficiency, supporting its good photoelectronic performance. The surface catalytic and adsorption/intercalation energy calculation reveals that the photogenerated electrons have adequate driving forces to render hydrogen reduction half-reactions to proceed spontaneously and the ability to cover and incorporate water molecules on the ?-PdS2 monolayer. Besides, the ?-PdTe2 monolayer is a promising donor material for excitonic solar cells with high photovoltaic performance. More importantly, due to suitable donor band gap and small conduction band offset in the proposed type-II heterostructure, the power conversion efficiencies (PCE) were calculated up to ?23% (?-PdTe2/WTe2), ?21% (?-PdTe2/MoTe2) and ?18% (?-PdTe2/?-PdS2), making it a promising candidate for solar energy conversion applications. � 2022 The Royal Society of Chemistry