The present disclosure relates to an optical film configured on a top of a light guide plate. The optical film is made of quantum dot (QD) material, and the optical film is filled with a plurality of diffusion particles configured to uniformly distribute incident light toward different angles. As such, the backlight emitted from the backlight module may be uniform and may be emitted toward different angles, the color difference and the chromaticity of the display device from different viewing angles may be the same, and the performance of the display device may be improved.