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Issue 37, 2010
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Design of star-shaped molecular architectures based on carbazole and phosphine oxide moieties: towards amorphous bipolar hosts with high triplet energy for efficient blue electrophosphorescent devices

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Abstract

With a carbazole moiety as the electron donor and a phosphine-oxide moiety as the electron acceptor, two novel star-shaped bipolar hosts, 4,4′,4″-tri(N-carbazolyl)triphenylphosphine oxide (TCTP) and 3,6-bis(diphenylphosphoryl)-9-(4′-(diphenylphosphoryl)phenyl)carbazole (TPCz), have been designed and synthesized. Their topology structure differences are that the phosphine-oxide moiety is located in the molecular centre and the periphery for TCTP and TPCz, respectively. The star-shaped architecture imparts them with high decomposition temperatures (Td: 497 °C for TCTP and 506 °C for TPCz) and results in the formation of a stable amorphous glassy state (Tg: 163 °C for TCTP and 143 °C for TPCz), while the phosphine oxide linkage ensures the disrupted conjugation and the high triplet energy (>3.0 eV). In addition, both TCTP and TPCz possess a bipolar transporting capability. However, TCTP mostly transports holes and TPCz primarily conducts electrons. On the basis of appropriate device configurations, high performance blue electrophosphorescent devices with comparable efficiency (35.0–36.4 cd A−1, 15.9–16.7%) have been realized using TCTP and TPCz as the host for the blue phosphor, respectively. Compared with the unipolar host, 4,4′,4″-tri(N-carbazolyl)triphenylamine (TCTA, 15.9 cd A−1, 7.8%), the efficiency is improved by more than two-fold. As far as the obtained state-of-the-art performance is concerned, we think that these novel materials should provide an avenue for the design of amorphous bipolar hosts with high triplet energy used for blue PhOLEDs on a star-shaped scaffold.

Graphical abstract: Design of star-shaped molecular architectures based on carbazole and phosphine oxide moieties: towards amorphous bipolar hosts with high triplet energy for efficient blue electrophosphorescent devices

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Article information


Submitted
27 Mar 2010
Accepted
29 Jun 2010
First published
19 Aug 2010

J. Mater. Chem., 2010,20, 8126-8133
Article type
Paper

Design of star-shaped molecular architectures based on carbazole and phosphine oxide moieties: towards amorphous bipolar hosts with high triplet energy for efficient blue electrophosphorescent devices

J. Ding, Q. Wang, L. Zhao, D. Ma, L. Wang, X. Jing and F. Wang, J. Mater. Chem., 2010, 20, 8126
DOI: 10.1039/C0JM00846J

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