Page 525 - Book Hosokawa Nanoparticle Technology Handbook

19 DENDRIMERS AND THEIR APPLICATION TO ORGANIC ELECTRONICS DEVICES APPLICATIONS
Recently, phosphorescent dyes have drawn much
attention as light-emitting materials because of their
high luminescence efficiency. In contrast with fluores-
cent dyes, the phosphorescent quantum efficiency can
reach nearly 100%, because both the single and triplet II-Conjugated
excited states contribute luminescence. However the shell
film of polymers doped with a phosphorescent dyes
like indium complex does not yield high luminescent Back electron
OLEDs because of their inhomogeneous film and/or transfer
dye’s aggregation. On the contrary, Samuel et al. syn-
thesized dendrimers with an indium complex, intro-
ducing an alkyl group at the terminal of a -conjugated
dendron for high affinity to the solvent. The casting
film from the mixture of this dendrimer, hole transfer
material (CBP) and electron transfer material (TPBI), Dye reduction Electrolyte
works as the high efficiency monolayer OLEDs [21].
On the other hand, TPA-DPAs are applied to a hole-
transporting layer [6, 7]. Though a triphenylamine
(TPA) has high crystallinity, the TPA-DPAs are easy to Figure 19.4
prepare a homogeneous film by cast. The OLEDs, Energy diagram of the dye sensitization solar cell using
using TPA-DPAs as a hole transfer layer and Alq as an TPA-DPA.
emitting layer, decrease not in the brightness but in the
electric current density as the generation advances, SnCl into the dendrimer enhances the fill factor because
2
resulting in the improvement of the luminescent effi- of the reduction in the resistance, leading to the improve-
ciency. The phenomena are attributed to the concen- ment of the energy conversion efficiency. In total, the
tration of the hole and electron density in the emitting energy conversion efficiency is improved by 34% by
layer; the large dendrimer shells suppress not the hole using the TPA-DPA G5 complex with SnCl [23].
transfer to the emitting layer but the electron pass from 2
the emitting layer. Additionally, the assembly of SnCl 2
into TPA-DPA improves the brightness and efficiency References
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accepter in this back electron transfer, I , complexes [11] L. Balogh, D.A. Tomalia: J. Am. Chem. Soc., 120,
3
with the imines at the branch structure of the den-

drimer at a ratio of 1:2, and then produces I working 7355–7356 (1998).
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Because of the above-mentioned synergy effect, the T. Goodson III: J. Chem. Phys., 114, 1962–1965 (2001).
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