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Fluoride crystals (BaY 2 F 8 ) doped with Er 3þ ions with different doping level have been grown with a home-made Czochralski furnace. A spectroscopic characterization consisting in both absorption and fluorescence measurements were performed in order to investigate the upconversion mechanism occurring when the material is excited with a radiation at 1557 nm. The measured emission spectrum shows a photoluminescence mainly distributed in the Near Infrared (NIR) region at '1 lm. The spectral conversion due to the upconversion makes this material suitable for photovoltaic applications, especially if we combine it with a crystalline silicon solar cell. A device made of single face solar cellþupconverter material (PV-UC) was designed and his external quantum efficiency (EQE) at 1557 nm was measured. EQE values of 6.5% and 4.1% were reached under 8.5 W cm -2 power density illumination for the 30%Er 3þ and 20%Er 3þ samples, respectively. V C 2013 AIP Publishing LLC. [http://dx.

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