a TBPe-doped emitting layer,52 implying the origin of the blue
emission of doped P(OF-SBF) films to be the dopant. In
addition, the excitation spectra of TBPe-doped P(OF-SBF)
films are perfectly superimposable to the absorption spectrum
of the undoped P(OF-SBF) film. These results demonstrate
that the excitation energy of P(OF-SBF) is efficiently trans-
ferred to the TBPe dopant to furnish a blue emission layer with
improved PL yield. It is noted that the emission intensity drops
in going from 1.5% to 5% dopant concentration. This may be
due to self-quenching of the dopant emission at higher
concentration.53,54
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Summary
A spiro-linked poly(terfluorene) was synthesized by copoly-
merization of 2,2’-dibromo-9,9’-spirobifluorene (4) and the
diboronate 5, via a palladium-catalyzed Suzuki coupling
reaction. In the spiro-fused bifluorene segment, the two
mutually perpendicular fluorene rings were connected via a
common tetracoordinated carbon atom, which served as a
conjugation interrupt to effectively control the conjugation
length of the polymer. Attributed to the spiro structure, the
polymer exhibits a higher glass transition temperature and
a more stable emission spectrum in comparison with the
conventional dialkyl polyfluorene. In TBPe-doped P(OF-SBF)
films, the excitation energy of P(OF-SBF) is efficiently trans-
ferred to the TBPe dopant to furnish a blue emission layer with
the color coordinates in CIE 1931 chromaticity measured to
be (0.147, 0.186). The utilization of P(OF-SBF) as a host matrix
for an emitting layer in electroluminescence applications is in
progress.
Acknowledgements
We thank the National Science Council of the Republic of
China for financial support. We also thank Dr. Banumathy
Balaganesan for providing the TBPe samples.
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