This paper deals with a luminescent layer applied on a commercial Silicon (Si) solar cell by spin coating of an aqueous solution of graphene quantum dots (GQDs), synthesized by the hydrothermal method at 200 °C for 24 h. The GQDs layer, acted as a luminescent down-shifting (LDS) layer, causes a relative enhancement in the short circuit current density (JSC) of mc-Si and c-Si solar cells up to 5.14% and 6.82%, respectively. Remarkable relative enhancements in JSC under UV illumination showed that the LDS layer increases the JSC by downshifting effect; Diffuse reflectance spectroscopy (DRS) of the solar cells with and without the LDS layers showed that the GQD filled LDS layers do not have a considerable effect on the light reflection from the Si solar cell to affect the JSC.