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 Yb0.80La0.15Tb0.05F3or Yb0.80La0.15Eu0.05F3nanoparticles 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 Tb3+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