DFT Study on Optoelectronic Properties of Graphene Quantum Dots with Various Sulfur Doping Patterns

Abstract

This study explores the effects of sulfur doping on the electronic and optical properties of Graphene Quantum Dots (GQDs) using Density Functional Theory (DFT). Three sulfur doping configurations are analyzed: substitutional doping (Sg), where sulfur atoms replace carbon atoms in the graphene lattice, edge/terminal doping (Sh), where sulfur is added at the edges or terminals, and thiophene-like doping (Sp), where sulfur is incorporated into five-membered rings at the graphene edges. The results show that sulfur doping reduces the energy gap of GQDs, with values of 1.444 eV for Sg, 1.213 eV for Sh, and 1.487 eV for Sp, indicating enhanced electrical conductivity and electronic reactivity. Optical absorption spectra reveal a redshift in the sulfur-doped GQDs compared to pristine GQDs, with absorption peaks at 858.7 nm for Sg, 1022.2 nm for Sh, and 833.9 nm for Sp, demonstrating their potential for applications in optoelectronic devices such as sensors and photodetectors. These findings highlight the significant impact of sulfur doping on the properties of GQDs, making them promising candidates for use in various nanoelectronic and optoelectronic applications.