Tuning the Electronic and Optical properties of Graphene and Boron-Nitride Quantum Dots through Molecular Charge-transfer Interactions

TL;DR

This study uses first-principles calculations to demonstrate how molecular charge-transfer dopants can significantly modify the electronic and optical properties of graphene and boron-nitride quantum dots, revealing potential for tunable nano-optoelectronic applications.

Contribution

It provides a detailed analysis of how TCNQ and TTF dopants interact with QDs, showing strong effects on their electronic structure and optical properties, which is a novel insight into quantum dot doping strategies.

Findings

Dopants are physisorbed on QDs with strong interaction with GQDs.

HOMO-LUMO gap decreases by more than half due to doping.

Spin-polarized HOMO-LUMO gaps observed in some complexes.

Abstract

Spin-polarized first-principles calculations have been performed to tune the electronic and optical properties of graphene (G) and boron-nitride (BN) quantum dots (QDs) through molecular charge-transfer using Tetracyanoquinodimethane (TCNQ) and Tetrathiafulvalene (TTF) as dopants. From our calculations, we find that the nature of interaction between the dopants and QDs is similar to the interaction between the dopants and their two-dimensional counter parts of the QDs, namely, graphene and hexagonal boron-nitride sheets. Based on the values of formation energy and distance between QDs and dopants, we find that both the dopants are physisorbed on the QDs. Also, we find that GQDs interact strongly with the dopants compared to the BNQDS. Interestingly, though the dopants are physisorbed on QDs, their interaction lead to a decrement in the HOMO-LUMO gap of QDs by more than half of their original value. We have also observed a spin-polarized HOMO-LUMO gap in certain QD-dopant complexes. Mulliken population analysis, Density of states (DOS), projected DOS (pDOS) plots and optical conductivity calculations have been performed to support and understand the reasons behind the above mentioned findings.