Synthesis, Properties, and Applications of Pure-hydrocarbon and Bipolar Host Materials For Electrophosphorescent Devices
Date Issued
2010
Date
2010
Author(s)
Ting, Hao-Chun
Abstract
There are two parts of this thesis. In the first part, we designed and synthesized a series of pure hydrocarbon host materials which exhibit suitable triplet energy levels for green and red phosphorescent OLED. In the molecular design, we combine aromatic rings and fluorenes to the indenofluorene core through spiro-linkage. By means of increasing steric hindrance in indenofluorene, we can prevent intermolecular interaction such as π-aggregates and excimer formation which may cause an additional emission band and a decrease in electroluminescence; therefore, thermal and morphological stability can be enhanced. The distance between phenyl and fluorene in InDSF is 3.29 Å, suggesting sufficient intramolecular π-π interaction. Devices incorporating with InDSF, InF3-tt, and ITS doped with Os or Ir complexes emitters as host materials showed the maximum EL quantum efficiency of 17.6%, 19.2% and 17.3% for electrophosphorescence, respectively. In this thesis, we will report the physical properties, X-ray structures, and device characteristics.In the second part, we synthesized the bipolar host materials combining electron-withdrawing benzimidazole and electron-donating indolocarbazole. Instead of using Fischer indolization which would lead to a mixture of products, we unitized condensation reaction of indole, formaldehyde, and triethoxymethane. This new synthetic route was not only time-saving but also with high yield for indolocarbazole. High performance of PhOLEDs have been reached with TICCBI and TICNBI as host materials. Among the devices, TICNBI-based device shows the maximum EL quantum efficiency of 22% and 16.2% for red and green electrophosphorescence, respectively.
Subjects
OLED
Type
thesis
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