Size-controlled graphene quantum dots with Inherent oxygen-containing groups for enhanced luminescent down-shifting (LDS) performance

Abstract

Graphene quantum dots (GQDs) have garnered significant attention as luminescent down-shifting (LDS) materials for photovoltaic applications, owing to their tunable emission properties and exceptional stability. In this study, GQDs were synthesized through the pyrolytic carbonization of citric acid, followed by size control via dialysis, to systematically investigate the effects of particle size and surface functional groups on their optoelectronic properties. Spectroscopic analyses revealed that reducing particle size significantly enhanced photoluminescence intensity and induced a pronounced ∼60 nm blue shift in the emission spectrum, indicating a stronger quantum confinement effect. Fourier-transform infrared spectroscopy confirmed the involvement of surface functional groups in modulating the optical characteristics of the GQDs. Cyclic voltammetry measurements further showed a clear size-dependent variation in the HOMO–LUMO energy gap, supporting the optical observations. These findings highlight the crucial influence of both size and surface chemistry on the optoelectronic behavior of GQDs, providing a scalable strategy for optimizing LDS efficiency.