Color filter substrate, method for fabricating the same, display panel and display device

The present invention provides a color filter substrate, comprising a plurality of pixel units, each pixel unit comprises a plurality of sub-pixel regions, wherein a filling cavity is formed in each sub-pixel region, at least the top wall of the filling cavity is transparent, each filling cavity is filled with quantum dots, the quantum dots in all the filling cavities are made of the same material, the particle diameters of the quantum dots in the same filling cavity are the same, the particle diameters of the quantum dots in the filling cavities of different sub-pixel regions of any pixel unit are different, and accordingly, the quantum dots in the filling cavities of different sub-pixel regions in any pixel unit can emit light of different colors after being excited. Accordingly, the present invention further provides a fabricating method of the color filter substrate, a display panel and a display device.