Up-conversion of 980 nm light into white light from sol-gel derived thin film made with new combinations of LaF3:Ln3+ nanoparticles

Abstract

White light was generated from SiO₂ and ZrO₂ sol-gel thin films made with four different combinations of lanthanide-doped nanoparticles. A 33-fold increase in the white light emission intensity was observed with the Commission Internationale de I'Eclairage (CIE) co-ordinates of 0.30, 0.34 from a silica thin film made with combination 2 (Yb/Tm and Yb/Er) nanoparticles when compared to our previous thin film. An absolute quantum yield of 0.1% for the green Er³⁺ emissions in this sample was determined by an absolute method using an integrating sphere. The quantum yield is defined as photons emitted divided by photons absorbed, so it runs from 0 to 100% for one-photon processes, from 0 to 50% for two-photon processes, etc. Similarly, silica thin films made with combination 1 (Yb/Tm, Yb/Ho, and Yb/Er), combination 3 (Yb/Tm, Yb/Tb, and Yb/Er) and combination 4 (Yb/Tm, Yb/Tb, and Yb/Eu) nanoparticles also produced white light with higher efficiency when compared to our previous thin film. ZrO₂ thin films made with these new combinations of nanoparticles also showed similar increases in the efficiency of white light.