Theoretical Study of the Interaction of Electron Donor and Acceptor Molecules with Graphene

Abstract

With the aim of understanding recent experimental data concerning noncovalent n/p-doping effects in graphene samples, we have investigated the interactions between two prototypical donor and acceptor molecules and graphene mono- and bilayer systems, by means of density functional theory calculations. We report and rationalize the structural, thermodynamical aspects, as well as charge transfers and the induced electronic structure modifications of the graphenic substrates in interaction with tetrathiafulvalene (TTF), an organic donor molecule, and tetracyanoethylene (TCNE), a typical acceptor. If the results show that p-doping of a graphene monolayer due to TCNE molecules can occur even at low concentration, n-doping of graphene requires either larger concentrations or cooperative adsorption of TTF molecules. In both cases, noncovalent doping only implies shifts of the Fermi level, and keeps the linear dispersion of the π and π* state around the Dirac point. Moreover, the intercalation of donor/acceptor molecules decouples the layers and doped them.

Band gap modulation of bilayer graphene by single and dual molecular doping: A van der Waals density-functional study

“…As in Ref. [24], we have investigated all the possible adsorption sites on the BLG models, in terms of energetic and geometric aspects. They are very similar to the monolayer case, with very small energy differences between adsorption sites.…”

“…Molecular doping is also an alternative by provoking asymmetric charge distribution in graphene layers. In a non-covalent doping process of graphene, the carrier concentration, which is a key feature for electronics, can be controlled by the concentration of the adsorbed molecules, without introducing significant lattice deformation [22][23][24][25]. Currently, graphene growth process only allows molecular dopants to be absorbed on the topside of the graphene layers, although intercalation cannot be completely excluded.…”

Computational chemistry for graphene-based energy applications: progress and challenges

“…116,117 Theoretical studies for these applications have typically investigated the electronic proprieties of graphene structures, since the majority of the publications in this area have reported use of QM calculations. 47,48,[118][119][120][121][122] Much of the interest of graphene for photovoltaic applications is due to its high charge-carrier mobility. 117,118 This is despite the fact that graphene is a zero-band gap semiconductor (i.e.…”

“…142 Doping graphene with non-covalently adsorbed molecules rather than covalent bonding species offers a number of advantages, in that it does not perturb the lattice and is also reversible. 122,157 Hu and Gerber recently investigated the non-covalent doping of graphene sheets by tetrathiafulvalene (TTF) and tetracyanorethylene (TCNE), comparing the effect of the LDA, PBE and vdW-DF functionals. 122 They found that by including the nonlocal correlation terms (via the vdW-DF functional) the strength of the binding between the dopants and the graphene sheet was significantly increased over not only the PBE but also the LDA functional.…”

“…122,157 Hu and Gerber recently investigated the non-covalent doping of graphene sheets by tetrathiafulvalene (TTF) and tetracyanorethylene (TCNE), comparing the effect of the LDA, PBE and vdW-DF functionals. 122 They found that by including the nonlocal correlation terms (via the vdW-DF functional) the strength of the binding between the dopants and the graphene sheet was significantly increased over not only the PBE but also the LDA functional. They also compared the effect of functional on the degree of charge transfer between the molecules and the graphene monolayer.…”