Tunable Optical Absorption of Graphene Quantum Dots with Transition Metal Adatom

This work presents an analysis of the optical properties of transition metal adatom-graphene quantum dot complexes (TM-GQDs). TM-GQDs with five metals (Cr, Mo, W, Pd, and Pt) and pristine GQDs were investigated to explore the possibility of engineering the optical characteristics. By Density Functional Theory and Time-Dependent Density Functional Theory, excited energy states and absorption spectra were analyzed. As a function of graphene quantum dot sizes and TMs, significant changes in HOMO-LUMO levels and optical transition energies were observed. The HOMO-LUMO gaps and energy levels in the visible range clearly indicate the adatom induced energy level shifts, showing smaller energy gaps in TM-GQDs than the pristine GQDs. The calculated THz absorption spectra show strong dependency on the size and adatom mass of TM-GQDs. The tunable optical properties of the TM-GQDs can be utilized as optical sources for future display applications.