Publication in Journal of Alloys and Compounds
Vol. 575, page 263-267, (2013)
by J. Méndez-Ramos, P. Acosta-Mora, J.C. Ruiz-Morales and N.M. Khaidukov
High intense UV-VIS upconversion luminescence from orthorhombic K2YF5 fluoride crystals doubly doped with Yb3+ and Er3+ has been obtained under near-infrared excitation at 980 nm. Fluoride crystals containing high Yb3+ concentrations, namely 20; 40 and 99 at.%, and low Er3+ concentrations have been synthesized under hydrothermal conditions. The role of the Yb3+ ions in the mechanism of the up-conversion process is clearly disclosed with absorption and up-conversion luminescence spectra from which one can see that high intense green (520-545 nm) and outstanding UV-blue (380-410 nm) emissions are greatly enhanced by increasing the concentration of Yb3+ which actsas an infrared collector harvesting long wavelength infrared photons. Outstanding total infrared to UV-VIS up-conversion efficiency of 66% has been calculated for the sample with highest Yb3+ doping level, i.e 99 at%.These strong UV-blue up-conversion emissions can enhance spectral response of main semiconductor electrodes, such as TiO2 and Fe2O3, and K2YbF5 crystals doped with Er3+ can be used in photoelectrochemical devices for sustainable production of hydrogen via photolysis of water.