Optimizing infrared to near infrared upconversion quantum yield of β-NaYF₄:Er³⁺ in fluoropolymer matrix for photovoltaic devices

The present study reports for the first time the optimization of the infrared (1523 nm) to near-infrared (980 nm) upconversion quantum yield (UC-QY) of hexagonal trivalent erbium doped sodium yttrium fluoride (beta-NaYF4:Er3+) in a perfluorocyclobutane (PFCB) host matrix under monochromatic excitation. Maximum internal and external UC-QYs of 8.4% +/- 0.8% and 6.5% +/- 0.7%, respectively, have been achieved for 1523 nm excitation of 970 +/- 43 Wm(-2) for an optimum Er3+ concentration of 25 mol% and a phosphor concentration of 84.9 w/w% in the matrix. These results correspond to normalized internal and external efficiencies of 0.86 +/- 0.12 cm(2)W(-1) and 0.67 +/- 0.10 cm(2)W(-1), respectively. These are the highest values ever reported for beta-NaYF4:Er3+ under monochromatic excitation. The special characteristics of both the UC phosphor beta-NaYF4:Er3+ and the PFCB matrix give rise to this outstanding property. Detailed power and time dependent luminescence measurements reveal energy transfer upconversion as the dominant UC mechanism. (C) 2013 AIP Publishing LLC.