Red, Green, and Blue Light Through Cooperative Up-Conversion in Sol-Gel Thin Films Made With ${\hbox{Yb}}_{0.80}{\hbox{La}}_{0.15}{\hbox{Tb}}_{0.05}{\hbox{F}}_{3}$ and ${\hbox{Yb}}_{0.80}{\hbox{La}}_{0.15}{\hbox{Eu}}_{0.05}{\hbox{F}}_{3}$ Nanoparticles

Abstract

Silica and zirconium dioxide sol-gel thin films made with Yb0.80La0.15Tb0.05F3 or Yb 0.80La0.15Eu0.05F3 nanoparticles are reported. Bright blue (413 and 435 nm), green (545 nm), and red (585 and 625 nm) emissions are produced from Tb3+ ions through cooperative up-conversion of 980 nm light. Similarly, red (591 and 612 nm) emission is generated from Eu3+ ions. These up-convertors may find use in white light sources. The cooperative up-conversion of Yb3+-Tb3+ ions is more efficient than of Yb3+-Eu3+ ions because the efficiency of energy transfer from excited Yb3+ ions to a Tb 3+ ion (0.37) is more than two-times higher than of excited Yb3+ ions to a Eu3+ ion (0.15), as estimated from the lifetime of excited Yb3+ ion. The estimated quantum yields of both Tb3+ ion and Eu3+ ion emissions are on the order of 40%, and hence are not the cause of the difference in efficiency. This approach does not work for Sm3+, Pr3+ , and Dy3+. Incorporation of the respective Ln3+ ions in nanoparticles is crucial, as controls, in which the various Ln3+ ions are incorporated directly into the sol-gel, that do not show cooperative up-conversion