In this study, we successfully prepared oxidatively functionalized graphene quantum dots (GQDs) to engineer the absorption band of a photoanode. By employing a facile hydrothermal process, we demonstrate the degree of intrinsic oxidation at the polar carbene edges of the GQDs, using Raman spectroscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The cyclic voltammetry results show that oxygen functional groups on the GQDs can change the highest occupied molecular orbital and lowest unoccupied molecular orbital levels. Dye-sensitized solar cells, with the GQDs dissolved in the dye, were evaluated in terms of their characteristics and conversion efficiencies. The GQDs dissolved in the dye were easily attachable to TiO₂ porous particles, and also contributed to the photoelectric conversion efficiency.