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

Silica and zirconium dioxide sol-gel thin films made with Yb
_0.80
La
_0.15
Tb
_0.05
F
₃
or Yb
_0.80
La
_0.15
Eu
_0.05
F
₃
nanoparticles are reported. Bright blue (413 and 435 nm), green (545 nm), and red (585 and 625 nm) emissions are produced from Tb
³⁺
ions through cooperative up-conversion of 980 nm light. Similarly, red (591 and 612 nm) emission is generated from Eu
³⁺
ions. These up-convertors may find use in white light sources. The cooperative up-conversion of Yb
³⁺
-Tb
³⁺
ions is more efficient than of Yb
³⁺
-Eu
³⁺
ions because the efficiency of energy transfer from excited Yb
³⁺
ions to a Tb
³⁺
ion (0.37) is more than two-times higher than of excited Yb
³⁺
ions to a Eu
³⁺
ion (0.15), as estimated from the lifetime of excited Yb
³⁺
ion. The estimated quantum yields of both Tb
³⁺
ion and Eu
³⁺
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
³⁺
, Pr
³⁺
, and Dy
³⁺
. Incorporation of the respective Ln
³⁺
ions in nanoparticles is crucial, as controls, in which the various Ln
³⁺
ions are incorporated directly into the sol-gel, that do not show cooperative up-conversion