Comparison between glass and glass-ceramic silica-hafnia matrices on the down-conversion efficiency of Tb3+/Yb3+ rare earth ions

In this paper, the investigation of energy transfer efficiency in Tb3+-Yb3+ co-doped SiO2-HfO2 glass and glassceramic waveguides is presented. Cooperative energy transfer between these two ions allows to cut one UV or 488 nm photon in two 980 nm photons and could have important applications in improving the performance of photovoltaic solar cells. Thin films with different molar concentrations of rare earths, up to a total concentration of 21%, were prepared by a sol-gel route, using dip-coating deposition technique on SiO2 substrates. The ratio between Yb3+ and Tb3+ ions in all the prepared thin films is constant and equal to 4. The energy transfer between Tb3+ and Yb3+ ions in glass and glass-ceramic waveguides shows the higher efficiency for glassceramic with a maximum quantum transfer efficiency of about 190% for the sample containing 19% of rare earths.