Optical properties of Eu doped CaF2 crystal for solar cell application

The high transparency CaF2 crystals have been made by the vertical Bridgman technique under the vacuum condition. Since low surface tension of CaF2 melt, crystal shape is controllable using mold crucible. We have been grown shaped crystals such as ribbon, triangle, and quadrilateral shaped crystals successfully and confirmed the grooves could be made on the crystal surface using this method. The Frenei lens was made using the crucible including many grooves inside. Eu doped CaF2 crystals have been made and we confirmed that the crystal ran effectively convert the UV light shorter than 400nm into 420nm. The Eu doped CaF2 crystal has the property of very low transmittance loss with a function of down convertion in UV region.