1：Experimental Design and Method Selection:

The study introduces a facile and cost-effective method to fabricate graphene quantum dots (GQDs) thin film on Fluorine-doped Tin Oxide (FTO) glass via casting of the GQDs dispersion and stabilizing with poly-vinyl-pyrrolidone (PVP).

2：Sample Selection and Data Sources:

GQDs were prepared by the pyrolysis of citric acid in a flask heated in a silicone oil bath. Different concentrations of GQDs (1, 2, and 3 g) were used to fabricate the thin film.

3：List of Experimental Equipment and Materials:

JEOL 2010 high-resolution transmission electron microscope (HRTEM), X-ray diffractometer (Shimadzu XRD-6000), atomic force microscope (AFM) (Asylum Research Cypher S), Fourier-transform infrared spectrophotometer (Perkin Elmer Spectrum), X-ray photoelectron spectrometer (XPS) (Kratos AXIS Supra), photoluminescence (Cary Eclipse spectrofluorometer), ultraviolet-visible (UV–vis) spectra (Cary 500 UV–vis-NIR spectrophotometer), DLF 1200 laser flash equipment (TA instrument).

4：Experimental Procedures and Operational Workflow:

The GQDs were prepared by the pyrolysis of citric acid at 200 °C in air for 0.5 h. The GQDs-PVP solution was stirred and ultra-sonicated for 30 min. each to obtain a homogenous dispersion. The GQDs thin films were obtained by drop-casting the precursor solution onto FTO glass and dried at 60 °C in air for 72 h.

5：5 h. The GQDs-PVP solution was stirred and ultra-sonicated for 30 min. each to obtain a homogenous dispersion. The GQDs thin films were obtained by drop-casting the precursor solution onto FTO glass and dried at 60 °C in air for 72 h. Data Analysis Methods:

5. Data Analysis Methods: The dot size was evaluated from the HRTEM images using the ImageJ software. The crystal structure and surface morphology of the GQDs thin film were characterized using an X-ray diffractometer and an atomic force microscope. The optical properties of the GQDs thin films were characterized by the photoluminescence and the ultraviolet-visible (UV–vis) spectra. The thermal diffusivity of FTO/GQDs thin film samples was measured with a DLF 1200 laser flash equipment.