Abstract
Silica and zirconium dioxide sol-gel thin films made with Yb<sub>0.80</sub>La<sub>0.15</sub>Tb<sub>0.05</sub>F<sub>3</sub> or Yb<sub>0.80</sub>La<sub>0.15</sub>Eu<sub>0.05</sub>F<sub>3</sub> nanoparticles are reported.
Bright blue (413 and 435 nm), green (545 nm), and red (585 and 625 nm) emissions
are produced from Tb<sup>3+</sup> ions through cooperative up-conversion of 980 nm light. Similarly,
red (591 and 612 nm) emission is generated from Eu<sup>3+</sup> ions. These up-convertors may find
use in white light sources. The cooperative up-conversion of Yb<sup>3+</sup> - Tb<sup>3+</sup> ions is more efficient
than of Yb<sup>3+</sup> - Eu<sup>3+</sup> ions because the efficiency of energy transfer from excited Yb<sup>3+</sup> ions to a Tb<sup>3+</sup> ion (0.37) is more than two-times higher than of excited Yb<sup>3+</sup> ions to a Eu<sup>3+</sup> ion (0.15), as estimated from the
lifetime of excited Yb<sup>3+</sup> ion. The estimated quantum yields of both Tb<sup>3+</sup> ion and Eu<sup>3+</sup> 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<sup>3+</sup>, Pr<sup>3+</sup>, and Dy<sup>3+</sup>. Incorporation of the respective Ln<sup>3+</sup> ions in nanoparticles is crucial, as controls, in which the various Ln<sup>3+</sup> ions are incorporated
directly into the sol-gel, that do not show cooperative up-conversion.
© 2007 IEEE
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