Nanoscale Interfaces of Janus Monolayers of Transition Metal Dichalcogenides for 2D Photovoltaic and Piezoelectric Applications

Abstract

Using first-principles calculations, we demonstrate a combination of two emergent fields, type II van der Waals heterostructures and Janus structures, for the purpose of optimizing the harvesting of solar and nano-electromechanical energy. The most stable stacking order in these nanoscale heterobilayers comprising Janus monolayers of transition metal dichalcogenides has been ascertained based on the interlayer binding energies. The binding energies in WSeTe/WSTe and MoSeTe/WSTe heterobilayers are found to be −27.93 and −25.67 meV/Å 2 at an equilibrium interlayer layer distance of 3.25 and 3.32 Å, respectively, indicating the exothermicity in the process of heterobilayer formation, and hence, its experimental feasibility. The mechanical and dynamical stabilities have also been confirmed for these heterobilayers using the Born Huang stability criteria and phonon dispersion calculations. Our results unveil the mechanism underlying the electronic, piezoelectric, photocatalytic properties, and carrier mobility in these Janus heterobilayers. The power conversion efficiency in the 2D ultrathin excitonic solar cells constituted by some of the heterobilayers studied in this work has been found to lie in the range of 15−20%. Moreover, a very high carrier mobility (>200 cm 2 /V•s) together with a large visible-light absorption coefficient (α ≈ 10 5 cm −1 ) has been observed in these heterobilayers. The piezoelectric coefficients in these ultrathin heterobilayers (d 33 = 13.91 pm/V) is found to reach close to the values obtained in multilayer/bulk structures built from Janus monolayers of Mo-based dichalcogenides. Our findings highlight the promising applications of these heterobilayers in ultrathin excitonic solar cells, nanoelectronics, and nanopiezotronics.

Photoelectrochemical Water‐Splitting Using CuO‐Based Electrodes for Hydrogen Production: A Review

“…Recently, TMDs with their unique crystal structures, superior properties, and exotic functionalities have drawn intense attention in applications for piezoelectric devices, [ 319–321 ] batteries, [ 322–324 ] electronic devices, [ 325,326 ] photocatalysis, [ 327–331 ] biomedicine, [ 332–334 ] and PEC sensing. [ 335,336 ] In this regard, 2D TMDs can play an important role in energy production in the future.…”

Piezotronics in two‐dimensional materials

“…since the first discovery of single atomic thickness graphene. Thus, piezotronics based on 2D materials was presented and developed rapidly from microscopic mechanism, various materials to the practical applications on nanogenerators, sensors, catalysis, information storage, and other flexible devices 42–54 …”

Recent advances in low-dimensional Janus materials: theoretical and simulation perspectives

“…Simulation of both classes of hetero-structures reveals type-II band alignment (staggered gap), where both the VBM and CBM of one component is a little higher than that of the other one, and accordingly favorable separation of excitons. Furthermore, Rawat et al [72] investigated a series of Janus hetero-structures formed by different kinds of Janus TMDs as MoXY/WXY (X, Y=S, Se, Te). They found that, depending on the composition and structure of the Janus TMD, the band gap can be tuned to a large extent from the infrared area to the ultraviolet region.…”

“…They found that, depending on the composition and structure of the Janus TMD, the band gap can be tuned to a large extent from the infrared area to the ultraviolet region. [72] In addition to hetero-structures consisting of two different Janus TMDs, research has also been carried out in other hetero-structures made up of Janus TMDs interfaced with other conventional two-dimensional materials. For instance, we investigated the heterostructure formed by combining Janus MoSSe with nitride semiconductors, namely MoSSe/XN (X=Al, Ga).…”