Excitons and light-emission in semiconducting MoSi2X4 two-dimensional materials

Abstract

Semiconducting two-dimensional materials with chemical formula MoSi2X4 (X = N, P, or As) are studied by means of atomistic ground- and excited-state first-principles simulations. Full-fledged quasi-particle bandstructures within the G0W0 approach substantially correct the electronic bandgaps previously obtained with hybrid-functional density functional theory and highlight the absence of lateral valleys close in energy to the conduction band minimum. By solving the Bethe–Salpeter equation, we show that the optical properties are dominated by strongly bound excitons with the absorbance and maximum short-circuit current densities of MoSi2P4 and MoSi2As4 comparable to those of transition metal dichalcogenides. Due to the presence of the outer SiX layers, the exciton binding energies are smaller than those generally found for transition metal dichalcogenides. Long radiative lifetimes of bright excitons, over 10 ns at room temperature for MoSi2As4, and the absence of band-nesting are very promising for application in efficient ultra-thin optoelectronic devices.

Electronic, optical, and transport properties of single-layer ZrTeS4: a DFT study

“…[66][67][68][69] Because single-layer ZrTeS 4 has a band gap of about 1.89 eV, it is interesting to discover the optical properties of this material. The optical properties can be described in good detail by including the exciton effect in G 0 W 0 + BSE calculations, 70,71 however this will significantly increase the computational cost for many strained structures of ZrTeS 4 . To give a general picture of the optical properties of single-layer ZrTeS 4 under different strains, the hybrid method HSE06 was used as this method is known to give acceptable accuracy in predicting optical properties of materials.…”

Two-dimensional MX2Y4 systems: ultrahigh carrier transport and excellent hydrogen evolution reaction performances

“…Since graphene with extraordinary properties was prepared, 1 two-dimensional (2D) materials always have been encouraged. [2][3][4][5][6][7][8] For graphene, the measured elastic stiffness and breaking strength are up to 340 N m À1 and 42 N m À1 , respectively. 9 The thermal conductivity tuned by the layer number was reported to be about 2800-1300 W m À1 K À1 .…”

Electronic and Excitonic Properties of MSi2Z4 Monolayers

“…The recent calculations within GW approximation and Bethe-Salpeter equation (GW + BSE) highlighted the band gap renormalization of more than 1.0 eV and exciton binding energy of several hundreds of meV. [44][45][46][47][48][49][50] The convergence of GW band gap and exciton binding energy with respect to calculation parameters was carefully checked only in refs. [47,48,50], yielding indirect and direct gap of 2.79-2.86 and 2.96-3.13 eV, respectively, and exciton A binding energy of 0.63-0.65 eV in 1L MoSi 2 N 4 .…”

“…[44][45][46][47][48][49][50] The convergence of GW band gap and exciton binding energy with respect to calculation parameters was carefully checked only in refs. [47,48,50], yielding indirect and direct gap of 2.79-2.86 and 2.96-3.13 eV, respectively, and exciton A binding energy of 0.63-0.65 eV in 1L MoSi 2 N 4 . Furthermore, since MA 2 Z 4 compounds are layered materials with band edges around the K points, the well-established effective modeling of exciton physics in TMDC-based systems [51][52][53][54][55][56][57][58][59][60][61] can be applied here as well.…”