Quantum Confinement Effects on Excitonic Properties in the 2D vdW quantum system: The ZnO/WSe₂ Case

Abstract

Quantum confinement effects play important roles in determining the electronic structures and optical properties of 2D quantum systems. Herein, the 2D ZnO/WSe2 van der Waals (vdW) system to study the influence of quantum confinement on excitonic optical properties, considering vdW heterobilayers (HBs), sandwiched trilayers (STs), and superlattice (SL), is taken. First‐principles calculations show that the quasiparticle (QP) bandgap, exciton binding energy, and band alignment depend obviously on quantum confinement. The QP bandgap and exciton binding energy decrease from 2.61 and 0.98 eV (HB) to 2.30 and 0.61 eV (ST), then to 2.02 and 0.28 eV (SL). Moreover, the conduction band offsets can be tuned from 0.87 eV (HB) to 0.79 eV (ST), then to 2.27 eV (SL). In addition, in ZnO/WSe2 vdW HB, increasing interlayer distance from 2.09 to 4.29 Å can induce exciton binding energy increase from 0.77 to 1.02 eV and QP bandgap increase from 2.49 to 2.62 eV. These results may be useful to tune excitonic properties and design optoelectronic devices by forming 2D vdW quantum systems.

Optoelectronic properties and applications of two-dimensional layered semiconductor van der Waals heterostructures: perspective from theory

“…As a result, the photo-generated electrons and holes of MoS 2 component will be transferred to SnSe 2 component, leading to a fast recombination between electrons and holes in the SnSe 2 /MoS 2 vdWHs. The same phenomenon was also found in the Ca(OH) 2 /α-MoTe 2 , arsenene/Ca(OH) 2 , C 2 N/In 2 SSe(In 2 STe) and ZnO/WSe 2 vdWHs due to the similar mechanism [56][57][58][59].…”

“…The enhancements of optical adsorption can contribute to the electron-hole interactions in the excitation process. For example, the intralayer excitons with low ionization energy can easily absorb low-energy photons and separate them into free electrons and holes (figures 3(d)-(f)), inducing the red shift of optical absorption threshold and the obvious exciton effects on the optical properties [56,57]. When Ca(OH) 2 layer combines with α-MoTe 2 layer, more intralayer excitons are generated and optical absorption in the heterostructure can be enhanced.…”

Probing 2D Exciton Dynamics of Non-Hydrogenic Anisotropic Rydberg Spectra in Anomalous Screening Regime

“…Figure 2 o , i.e., the difference between the first peak of the G 0 W 0 +RPA spectra and the G 0 W 0 +BSE spectra. 53,54 It is evident that both the SSH and RK models align well with binding energy calculated by the rigorous G 0 W 0 + BSE approach (Table 1). Thus, they are suitable for subsequent analyses we plan to conduct in this study using these models.…”

Quantum-sized topological insulators/semimetals enable ultrahigh and broadband saturable absorption

“…Such effects would change the electronic structure, exciton properties and density of states of the as-produced QSs, directly affecting the changes of its nonlinear absorption coefficient, saturation intensity and excited state dynamics, resulting in ultrahigh saturable absorption. [50][51][52] Evidently, the combination of the inherent characteristics of the material, quantum confinement and intrinsic edge effects could be determinative to their phenomenal NSA performances of the quantum-sized topological insulators and semimetals.…”