Display substrate having wide-color gamut, its manufacturing method, display panel and display device

A method for manufacturing a display substrate, comprising:

• providing a base substrate;
• and
• forming, on the base substrate, a composite film structure composed of at least two thin films having different refractive indexes, wherein the composite film structure is configured to absorb light with a wavelength in a predetermined wavelength range, and the predetermined wavelength range is located between two adjacent peaks of visible light waves, and wherein the composite film structure comprises a silicon dioxide thin film and a silicon nitride thin film superposed one on another, the silicon nitride thin film completely overlaps with the silicon dioxide thin film and is in direct physical contact with the silicon dioxide thin film, the silicon nitride thin film has a thickness between 450 and 495 angstroms, the silicon dioxide thin film has a thickness between 1800 and 2200 angstroms, and the silicon dioxide has a refractive index of 1.4 and the silicon nitride has a refractive index of 1.8 such that the composite film structure is able to absorb light having a wavelength near 580 nm.