The invention discloses a solar absorbing film. The solar absorbing film comprises a bottom-layer
metal sheet Cu, an absorbing layer and an AlN antireflection layer formed through reactive
sputtering in sequence, wherein the absorbing layer comprises multiple absorbing period
layers; each period layer comprises two
layers of effective absorbing layer films; the effective absorbing layer films are
metal-layer Ni films and
ceramic absorbing-layer TiNxOy-Ni films from top to bottom in sequence; and the
metal-layer Ni films are 5-8 nm thick. The invention further discloses a preparation method. The preparation method comprises procedures of pretreatment of the bottom-layer
metal sheet, deposition of the absorbing layer and high-vacuum heat annealing; the procedure of deposition of the absorbing layer adopts a three-target direct-current magnetron
sputtering method; and the
coating deposition is performed with TiO2 having the purity of 99.9 wt%, metal Ni having the purity of 99.99 wt% and metal Al having the purity of 99.99 wt% as
sputtering targets. The solar absorbing layer adopts design thoughts of multistage
layered structure and component gradient, so that the absorbing layer has both characteristics of multistage
layered structure and component gradient; the absorption / emission rate is optimized; and the solar absorbing film also has the characteristics of
corrosion resistance and
oxidation resistance, the
coating working reliability is guaranteed, and the comprehensive performance of a blue
titanium selective absorption
coating layer is further enhanced.