| Summary: | 碩士 === 元智大學 === 光電工程學系 === 102 === By studying five bipolar compounds named as CbzOXD-1, CbzOXD-2, CbzTAZ-1, CbzTAZ-2 and CbzTAZ-3 to be the host of blue and blue-green phosphorescent (Ph) organic light emitting diode (OLED), the characteristics of these OLEDs are disclosed in this thesis. These ambipolar derivatives are synthesized by applying carbazole on 2-phenyl-5-(2',4',6'-trimethyl-[1,1'-biphenyl]-4-yl)-1,3,4-oxadiazole (OXD) and 3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2.4-triazole (TAZ) to become the five new compounds. The main idea is to synthesize the ambipolar materials utilizing carbazole with the excellent hole transporting and high triple energy, to assist the electron transporting materials (OXD and TAZ).
The organization of this thesis: chapter 1, the history, principle, current and future development of OLEDs will be introduced in this part. In addition, we summary several relative reports and discuss their reported the improvement of efficiency. Chapter 2, the detail experimental process, device fabrication, measurement will be addressed. Chapter 3, the characteristics of these five novel compounds will be discussed such as absorption spectrum, photoluminescence spectrum, low unoccupied molecular orbit (LUMO), high occupied molecular orbit (HOMO). Then, we use these five compounds to be the host doping with iridium(III)bis[(4,6-difluorophenyl)-pyridinato-N,C2’] picolinate (FIrpic) as emitting layer inside the blue PhOLED. By well tuning the dopant concentration, the high efficiency blue PhOLED can be obtained. Chapter 4, to optimize the current efficiency of blue PhOLED, the adjustment in the thickness of electron transporting layer (ETL) and emitting layer (EML) will be employed to find the optimal device structure with 45 nm ETL and 40 nm EML. The blue PhOLED shows current efficiency of 47.95 cd/A, power efficiency of 42.16 lm/W and external quantum efficiency (EQE) of 22.94%. In addition, the purified FIrpic will be also employed to achieve the maximum current efficiency of 52.1 cd/A. Chapter 5, the blue-green PhOLED is also investigated by adding the green dopant into the former blue PhOLED to achieve the high efficiency and high color stability. The conclusions and future work about this thesis will be carefully given in the Chapter 6.
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