Strong 1.53 μm to NIR-VIS-UV upconversion in Er-doped fluoride glass for high-efficiency solar cells

Optical spectra of Er-doped modified ZBLAN glasses are studied at room temperature. Radiative quantum yields of the 4I11/2 and 4I13/2 levels are estimated from the experimentally measured lifetimes and from the spontaneous emission probabilities calculated from the Judd-Ofelt theory. The spectra of upconversion (UC) luminescence excited with 1.53 μm cw Er fiber laser are investigated in a wide spectral domain [from the near-infrared (NIR) to UV]. Absolute UC efficiency (i.e., the ratio of UC luminescence power to the absorbed pump power) is experimentally measured; efficiency of up to 12.7% is obtained. A conclusion is made about perspectives of use of the studied glasses as upconverter material for solar cells of enhanced efficiency.