NOVELTY - The radiation collecting device such as a photovoltaic module comprises a radiation collector element, and a diffusion layer (2) arranged with respect to the collector element on one side of incidence of the radiation on the device. The diffusion layer comprises a transparent fibrous structure and a transparent medium for encapsulating the fibers of the fibrous structure. The absolute value of the difference between the refractive index of fibers of the fibrous structure and the refractive index of the encapsulating medium is greater than or equal to 0.05.    USE - Used as a radiation collecting device such as a photovoltaic module.    ADVANTAGE - The radiation collecting device exhibits high energy conversion efficiency and improved performance, and ensures high collection of radiation with less consumption of energy.    DETAILED DESCRIPTION - The radiation collecting device such as a photovoltaic module comprises a radiation collector element, and a diffusion layer (2) arranged with respect to the collector element on one side of incidence of the radiation on the device. The diffusion layer comprises a transparent fibrous structure and a transparent medium for encapsulating the fibers of the fibrous structure. The absolute value of the difference between the refractive index of fibers of the fibrous structure and the refractive index of the encapsulating medium is greater than or equal to 0.05. The encapsulating medium is made of a polymer material, and formed by an interlayer of polymer lamination and a front substrate (1) of the device. The fibrous structure is a non-woven veil (3), comprises glass fibers and polymer fibers, and has a surface mass of 10-100 g/m2, where fibers have a diameter of 5-15 mu m. The diffusion layer has a total light transmission of greater than or equal to 80% and a blur value of greater than or equal to 40%, and is arranged against a front electrode of the radiation collector element. The absorbing material has a first absorption spectrum and a second absorption spectrum partially detached from the first absorption spectrum. The diffusion layer is interposed between a first photovoltaic cell and a second photovoltaic cell of the photovoltaic module. An INDEPENDENT CLAIM is included for a cover for a radiation collector element.    DESCRIPTION OF DRAWING(S) - The diagram shows a cross-sectional view of a photovoltaic solar module.    Front substrate (1)    Diffusion layer (2)    Transparent veil (3)    Transparent matrix (4)    Transparent layer (5)    Wafer. (6)