Improvements of an up-conversion NaYF/sub 4/:Er/sup 3+/ phosphor/silicon solar cell system for an enhanced response in the near-infrared

This study investigates the performance of up-converting rare-earth phosphors doped with different trivalent erbium (Er/sup 3+/) concentrations: 2%, 20%, 50%, 100%, and with the addition of 20% ytterbium (Yb). The dominant up-conversion (UC) mechanisms within these phosphors are discussed and examined using photoluminescence and the spectral response from a bifacial silicon solar cell. The most efficient phosphor examined had 20% Er doping and gave a maximum external quantum efficiency close to 3.4% with 6 mW 1523 nm laser excitation. The subsequent system internal quantum efficiency (accounting for reflection losses within the cell) is calculated to be over 5.7%.