NOVELTY - The luminescent solar energy concentrator (1) comprises a waveguide comprising a transparent matrix (2). The transparent matrix has particles of an inorganic luminescent material. The waveguide is associated with a photovoltaic cell so that light emitted from the luminescent material passes into the photovoltaic cell to generate a voltage in the cell, where a difference of the refractive index of the inorganic luminescent material and the refractive index of the transparent matrix both measured at the emission peak of the inorganic luminescent material is less than or equal to 0.4.    USE - The luminescent solar energy concentrator is useful for a photovoltaic cell.    ADVANTAGE - The luminescent solar energy concentrator exhibits high efficiency.    DETAILED DESCRIPTION - The luminescent solar energy concentrator (1) comprises a waveguide comprising a transparent matrix (2). The transparent matrix has particles of an inorganic luminescent material. The waveguide is associated with a photovoltaic cell so that light emitted from the luminescent material passes into the photovoltaic cell to generate a voltage in the cell, where a difference of the refractive index of the inorganic luminescent material and the refractive index of the transparent matrix, both measured at the emission peak of the inorganic luminescent material is less than or equal to 0.4 and both measured at the absorption peak of the inorganic luminescent material is greater than or equal to 0.02. The transparent matrix material comprises high-index organic polymers, organic polymers having inorganic particles, silicone polymers and/or resins, and/or inorganic matrix materials. The inorganic luminescent material is provided in particle form, and the average diameter of the particles is greater than or equal to 100 nm and less than or equal to 5 mu m.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic cross-sectional view of a luminescent solar energy concentrator and a solar cell.    Solar energy concentrator (1)    Transparent matrix (2)    Light guide (3)    Solar cell. (4)