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

Abstract

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 (b-NaYF4:Er3þ) in a perfluorocyclobutane (PFCB) host matrix under monochromatic excitation. Maximum internal and external UC-QYs of 8.4%60.8% and 6.5%60.7%, respectively, have been achieved for 1523 nm excitation of 970643Wm 2 for an optimum Er3þ 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 0.8660.12 cm2W 1 and 0.6760.10 cm2W 1, respectively. These are the highest values ever reported for b- NaYF4:Er3þ under monochromatic excitation. The special characteristics of both the UC phosphor b-NaYF4:Er3þ 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.