Abstract
We demonstrate that photoluminescence (PL) quantum yield and PL lifetime
of fac-tris(2-phenylpyridyl)
iridium(III) [Ir{ppy}<sub>3</sub>]-cored dendrimers in neat film and dispersed into a 4,4'-bis(N-carbazolyl)biphenyl host can be significantly improved by a simple adjustment of the solution preparation. Quenching of the PL in
these materials is due to an energy transfer of the triplet excitons to less-emissive
sites and can be reduced by blending the phosphorescent molecules into a suitable
wide energy gap host or by increasing the number of attached dendrons. We
show here that the concentration of these quenchers can also be controlled
by changing the time spent by the dendrimer solution under illumination prior
to spin-coating. By optimizing the film preparation procedure, the external
efficiency of devices made from neat dendrimer films was increased from 2%
to 10%.
© 2007 IEEE
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