NOVELTY - Luminescent solar concentrator comprises a transparent waveguide (14), and a transparent film including transparent luminophores (18), which is operable to absorb light in the UV spectrum and emit light in the near-infrared spectrum.    USE - The luminescent solar concentrator is useful in a window of a building (all claimed) such as a structural building including solar towers and obelisks, greenhouses, automotive vehicle, aircraft and watercraft.    ADVANTAGE - The luminescent solar concentrator exhibits improved luminophore photoluminescence efficiency and lifetimes, improved solar spectrum absorption efficiency, waveguide (trapping) efficiency, solar cell efficiency, transport (reabsorption) efficiency, building efficiency, and phosphorescent and fluorescent luminophore efficiencies.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a window (31) comprising a first glass panel including a first transparent film and a second glass panel including a second transparent film opposite to the first glass panel, where the first transparent film includes first transparent luminophores, which are operable to absorb light in the UV spectrum and emit light in the near-infrared spectrum, and the second transparent film includes second transparent luminophores, which are operable to absorb light in the near-infrared spectrum and emit light in the near-infrared spectrum;    (2) a transparent luminophore comprising a metal compound of formulae (MX2.L2) (I), (AMX2.L2) (II), (M6X12.L2) (III), (A2M6X14) (IV) and (A2M6X14.L2) (V); and    (3) fabricating a transparent polymer composite film comprising mixing a solution including an acetonitrile solution with a (poly)-ethyl methacrylate acetonitrile solution and a (poly)-methyl methacrylate solution at a volume ratio of 1:2:1, casting the solution on a substrate, and drying the solution to form the transparent composite film.    M = W or Mo;    X = Cl, Br or I;    L = Cl, CH3CN, benzenethiol, ethanethiol, hydrate, HCl or acetonitrile; and    A = K, Na, tetrabutylammonium or other ammonium salts.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a luminescent solar concentrator.    Transparent waveguide (14)    Panes (15)    Transparent luminophores (18)    Building (30)    Windows. (31)