Modulating Carrier Density and Transport Properties of MoS₂ by Organic Molecular Doping and Defect Engineering

Abstract

Using first-principles calculations, we investigate the effect of molecular doping and sulfur vacancy on the electronic properties and charge modulation of monolayer MoS2. It is found that tetrathiafulvalene and dimethyl-p-phenylenediamine molecules are effective donors, whereas tetracyanoethylene (TCNE) and tetracyanoquinodimethane (TCNQ) are effective acceptors, and all these molecules are able to shift the work function of MoS2. For MoS2 containing sulfur vacancies, these molecules are able to change the position of the defect levels within the band gap and modulate the carrier density around the defect center. Charge transfer analysis shows that TCNE and TCNQ induce a free-carrier depletion of the defect states, which is beneficial for the suppression of the nonradiative trionic decay and a higher excitonic efficiency due to a decrease in the screening of excitons. Furthermore, the effects of molecular adsorption on Seebeck coefficient of MoS2 are also explored. Our work suggests that an enhanced excitonic efficiency of MoS2 may be achieved via proper defect engineering and molecular doping arising from the charge density modulation and charge screening.

The improvement of photocatalytic activity of monolayer g-C3N4viasurface charge transfer doping

“…3), in accordance with the literature reports. 40,56 These phenomena indicate that the monolayer g-C 3 N 4 may be tuned into p/n-type materials by doping with the electron-withdrawing/donating TCNQ and TTF molecules.…”

“…Carrier concentration and even conduction type of the semiconductor nanostructures can be readily tuned by varying the types as well as densities of surface dopants, leading to effective p-and n-type doping on the nanostructures. [33][34][35] SCTD has been proven to be a simple, nondestructive, and effective method to tune both the electronic and optical properties of low-dimensional semiconductors, [36][37][38][39][40][41][42][43][44] which is of fundamental importance to enable their wide applications in optoelectronic and electronic devices. For example, the electronic properties and carrier density of monolayer MoS 2 monolayer could be effectively modulated with electron acceptor, tetracyanoquinodimethane (TCNQ), and electron donor, tetrathiafulvalene (TTF).…”

Strain-enhanced properties of van der Waals heterostructure based on blue phosphorus and g-GaN as a visible-light-driven photocatalyst for water splitting

“…[65][66][67][68] Using the Vienna Ab Initio Simulation Package (VASP), the exchange correlation functional was expressed by the Perdew-Burke-Ernzerhof (PBE) functional with generalized gradient approximation (GGA). [69][70][71][72][73] To obtain more accurate bandgap values and results, the hybrid Heyd-Scuseria-Ernzerhof (HSE06) functional was also adopted. [74][75][76] More specically, the cut-off energy was set at 550 eV, and the atoms in the rst Brillouin Zone (BZ) was conducted via 7 Â 7 Â 1 and 17 Â 17 Â 1 Monkhorst-Pack k-point grids for relaxation and static calculations, respectively.…”

Controlling neutral and charged excitons in MoS2 with defects

“…Fabrication of MoS 2 by chemical vapor deposition (CVD), mechanical exfoliation, and physical vapor deposition introduces intrinsic defects, which has been shown to degrade material's properties [16]. Carbon and oxygen impurities introduced at various stages of fabrication can occupy interstitial sites in MoS 2 [17], act as traps for charge carriers [18], and degrade carrier concentrations [19].…”