Publication date: 15th December 2025
Graphene, a two-dimensional sp2 carbon lattice with a Dirac-type band dispersion, making it an attractive platform for non-covalent organic functionalization in optoelectronic [2] and sensing devices, where interfacial charge transfer (CT) tuning is a key. Here, we investigate a family of dibenzo[a,i]pyrene (DBP) derivatives adsorbed on graphene monolayer to understand why experimentally detectable CT is observed for pristine DBP, while chemically modified DBP analogues do not show the expected CT response.
We employ density-functional theory calculations within VASP [1] to characterize the ground-state electronic structure of graphene–DBP heterojunctions, including adsorption geometries and interfacial energetics. For each interface we analyze the density of states and band structure, WF shifts from the electrostatic potential in the vacuum region, and evaluate charge rearrangement using Bader charge analysis.
To connect ground-state descriptors with CT efficiency, we additionally evaluated adiabatic orbital couplings relevant to charge-transfer kinetics. This allows us to go beyond a static orbital alignment argument and discuss whether interfaces with comparable thermodynamic driving forces can still differ in CT observability due to electronic coupling. The coupling analysis supports a mechanistic interpretation in which chemical functionalization can inadvertently reduce the effective π–π interaction thereby suppressing kinetically efficient CT pathways even when Bader-derived trends predict a donor-like character. In contrast, pristine DBP maintains a favorable combination of measurable donor-to-graphene charge transfer reflected in both Bader charges and WF shift as well as sufficiently strong orbital coupling to sustain efficient CT.
Overall, our results provide a consistent theoretical framework linking WF shift and Bader charge transfer with the directionality of doping. They also suggest practical design rules for DBP derivatives: substitutions should preserve planarity and close adsorption to maintain orbital coupling, while tuning donor strength to control the magnitude of WF shift and charge transfer. These insights guide the selection of DBP derivatives with potentially enhanced CT performance at graphene–molecule interfaces.
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