Characterization and Device Applications of High-Triplet-Energy Organic Semiconductors
Date Issued
2010
Date
2010
Author(s)
Huang, Shih-Hsuan
Abstract
Organic Light Emitting Device (OLED) technology is emerging as a promising technology for displays and lighting. OLEDs possess key performance features including vibrant color, high contrast ratios, full-motion video, and wide viewing angles. In two different light-emitting mechanisms, phosphorescent OLEDs can have up to four times higher efficiency than fluorescent OLEDs, because the incorporation of heavy metal-containing complexes into appropriate host materials allows the harvesting of both singlet and triplet excitons and make it possible to achieve nearly 100% internal quantum efficiency. The development of PHOLED therefore has attracted a great deal of attention, and the adoption of bipolar host materials is becoming an important method to improve device performances.
Two novel materials were under studied in this research. Materials combining carbazole-based main structures, which are considered to give hole-transport ability, and sulfone group, which is expected to be electron-transport part of the molecule, is believed to give bipolar ability, and the large triplet energy (> 2.8 eV) is suitable for PHOLED host materials. Both two materials have high PLQY about 80% when doping with Ir(ppy)3 and FIrpic, but the devices can’t reach equal performances. The properties of these two materials in devices were studied by applying different materials into the hole-transport layer and the electron-transport layer. Having more sulfone groups, cbz-di-SO2 shows stronger electron-transport property than SO2mCP.
Subjects
Sulfone
carbazole
high-treplet
phosphorescence
OLED
bipolar
Type
thesis
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