NOVELTY - The light selectively absorbing layer consists of composite film formed by reacting an iron-chromium alloy and non-metal gas using vacuum plating technology. The iron-chromium alloy contains iron (60-87 wt.%) and chromium (13-25 wt.%) or optionally several alloying elements. The total amount of metal in the metal-dielectric composite film is 40-75 mol%. The vacuum plating technology is vacuum evaporation technology magnetron sputtering technology, preferably magnetron sputtering technology.    USE - For solar energy collector element or solar energy selectively absorbing coating system.    DETAILED DESCRIPTION - The light selectively absorbing layer consists of composite film formed by reacting an iron-chromium alloy and non-metal gas using vacuum plating technology. The iron-chromium alloy contains iron (60-87 wt.%) and chromium (13-25 wt.%) or optionally several alloying elements. The total amount of metal in the metal-dielectric composite film is 40-75 mol%. The vacuum plating technology is vacuum evaporation technology magnetron sputtering technology, preferably magnetron sputtering technology. The non-metal gas contains mixture gas containing oxygen and nitrogen. The nitrogen containing gas is nitrogen gas and/or ammonia gas, preferably nitrogen gas. The mixture gas contains nitrogen gas and/or hydrocarbon gas. The iron-chromium alloy is austenite stainless steel, preferably AISI 304(0Cr18Ni9) (RTM: stainless steel) or AISI 316L(00Cr17Ni14Mo2) (RTM: stainless steel). The solar cell collector element or solar energy selectively absorbing coating system has infrared high reflective bottom layer which consist of copper, aluminum, molybdenum, nickel or their alloy and antireflection layer which consists of nickel-based nitride, tin-metal nitride film or aluminum oxide, aluminum-nitride, aluminum-oxynitride and their mixture film. The substrate of solar energy collector element or solar energy selectively absorbing coating system is copper or stainless coated with copper film.    An INDEPENDENT CLAIM is included for method of preparing light selectively absorbing layer.