A solar energy absorbing device includes a substrate and a solar selective absorber film. The solar selective absorber film has a bottom surface attached on the substrate, and a top surface opposite to the bottom surface. The solar selective absorber film is a TiNxOy based film, and x and y vary from 1 to 0.1 and 0.2 to 2, respectively, from the bottom surface to the top surface of the solar selective absorber film.