School Of Basic And Applied Sciences
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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, AshokIn 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.Item Janus ?-Te2X (X = S, Se) monolayers for efficient excitonic solar cells and photocatalytic water splitting(Royal Society of Chemistry, 2023-01-04T00:00:00) Singh, Jaspreet; Kumar, AshokHighly efficient, environmentally friendly and renewable sources of energy are of great need today to combat increasing energy demands and environmental pollution. In this work, we have investigated the novel 2D allotropes, i.e., ?-Te2X (X = S, Se), using first-principles calculations and study their potential applications in light harvesting devices. Both the monolayers possess high stability and semiconducting nature with an indirect band gap. The high carrier mobilities and excellent optical absorption of these monolayers make them potential candidates for solar conversion applications. We have proposed the type-II heterojunction solar cells and calculated their power conversion efficiencies (PCEs). The small conduction band offset and appropriate band gap of donor material in the case of ?-Te2S(S-Side)/?-Te2S(Te-Side) heterojunction results in a PCE of ?21%. In addition, the band alignments of these monolayers properly engulf the redox potentials of water. The overpotentials required to trigger hydrogen reduction (HER) and water oxidation (OER) half reactions reveal that HER and OER preferred acidic and neutral media, respectively. The calculated solar-to-hydrogen (STH) efficiencies of ?-Te2S (?-Te2Se) monolayers turn out to be ?13% (?12%), respectively, which implies their practical applications in water splitting. Thus, our work provides strong evidence regarding the potential applications of these materials in the field of light harvesting devices. � 2023 The Royal Society of Chemistry.Item Mechanical, optical and thermoelectric properties of Janus BiTeCl monolayer(Elsevier Ltd, 2022-04-29T00:00:00) Chauhan, Poonam; Singh, Jaspreet; Kumar, AshokWe report mechanical, optical and thermoelectric properties of recently fabricated Janus BiTeCl monolayer using density functional and semi-classical Boltzmann transport theory. Janus BiTeCl monolayer exhibits a direct bandgap, high carrier mobility (?103 cm2V?1s?1) and high optical absorption in the UV�visible region. The mechanical behavior of the Janus BiTeCl monolayer is nearly isotropic having an ideal tensile strength ?15 GPa. The higher value of the Gruneisen parameter (?), a low value of phonon group velocity (vg), and very little phonon scattering time (?p) lead to low lattice thermal conductivity (1.46 W/mK) of Janus BiTeCl monolayer. The combined effect of thermal conductivity and electronic transport coefficients of Janus BiTeCl monolayer results in the figure of merit (ZT) in the range of 0.43�0.75 at 300�500 K. Our results suggest Janus BiTeCl monolayer be a potential candidate for optoelectronic and moderate temperature thermoelectric applications. � 2022