Improved sensitization efficiency in Er3+ ions and SnO2 nanocrystals co-doped silica thin films

Er3+ ions and SnO2 nanocrystals co-doped silica thin films are prepared by an improved sol–gel spin-coating method. With increase in annealing temperature, the related 1.54 μm characteristic emission intensity from Er3+ ions is obviously enhanced by more than two orders of magnitude via SnO2 nanocrystals size control to boost the sensitization efficiency. Quantitative studies of steady-state spectroscopic data and fluorescence decay curves demonstrate that the related sensitization efficiency via size-tunable nanocrystals is increased from 0.14% to 1.3%. This improved sensitization efficiency is achieved by doping some of the Er3+ ions into the SnO2 inner sites at a high annealing temperature, as revealed by high-resolution TEM, X-ray diffraction patterns and elemental mapping technique. Different sensitization mechanisms are also discussed separately according to the selective photoluminescence excitation measurements. All these results have not only explained the greatly improved sensitization efficiency resulting from SnO2 nanocrystals but also indicated that the development of Er3+ ions and SnO2 nanocrystals co-doped silica thin films could result in promising high-performance near-infrared luminous materials using broadband UV pumping.