NOVELTY - A solar radiation conversion device comprises luminescent thulium (II) inorganic material for converting greater than or equal to 1 part of UV and/or visible and/or infrared solar radiation into infrared radiation, preferably infrared radiation having a wavelength of 1138 nm, and photovoltaic device for converting greater than or equal to 1 part of infrared radiation into electrical power.    USE - A solar radiation conversion device (claimed).    ADVANTAGE - Luminescent material has improved broadband absorption even at large part of solar spectrum. Self-absorption is prevented. Overall conversion efficiency of simple single-junction solar cells is improved.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) utilization of luminescent thulium (II) inorganic crystalline material in luminescent solar energy concentrator or solar cell;    (2) synthesis of luminescent thulium (II) doped inorganic crystalline material which involves melting an amount of greater than or equal to 1 1st inorganic ionic compound with 2nd inorganic ionic compound such as thulium (II) or thulium (III) cation in order to form thulium (II) doped 1st ionic compound, and maintaining pressure at less than or equal to 5.1-4 mbar, preferably less than or equal to 1.1-4 mbar during melting; and    (3) formation of luminescent thulium (II) doped inorganic polycrystalline thin-film on substrate mounted in evacuated chamber which involves providing 1st sputtering target with 1st sputtering material containing 1st inorganic ionic compound and 2nd sputtering target with 2nd sputtering material such as thulium, introducing gas into sputtering chamber, heating the substrate to 10-700 degrees C, preferably 10-600 degrees C and applying radio frequency (RF) electric potential to 1st sputtering target and direct current electric potential to 2nd sputtering target to grow (poly)crystalline thin-film of 1st inorganic ionic compound.    DESCRIPTION OF DRAWING(S) - The drawings show a schematic cross-sectional view of the luminescent solar energy concentrators containing thulium doped inorganic material.    Waveguide structure (902)    Top surface (903)    Bottom surface (905)    Photovoltaic cell (908)    Particles (910)