Red, Green, and Blue Light Through Cooperative Up-Conversion in Sol-Gel Thin Films Made With Yb0:80La0:15Tb0:05F3 and Yb0:80La0:15Eu0:05F3 Nanoparticles

Silica and zirconium dioxide sol-gel thin films made with Yb0 80La0 15Tb0 05F3 or Yb0 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 Tb ions through cooperative up-conversion of 980 nm light. Similarly, red (591 and 612 nm) emission is generated from Eu ions. These up-convertors may find use in white light sources. The cooperative up-conversion of Yb Tb ions is more efficient than of Yb Eu ions because the efficiency of energy transfer from excited Yb ions to a Tb ion (0.37) is more than two-times higher than of excited Yb ions to a Eu ion (0.15), as estimated from the lifetime of excited Yb ion. The estimated quantum yields of both Tb ion and Eu 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 Sm, Pr, and Dy. Incorporation of the respective Ln ions in nanoparticles is crucial, as controls, in which the various Ln ions are incorporated directly into the sol-gel, that do not show cooperative up-conversion.