Applications of Imprint Lithography for High-EfficiencyOrganic Light-Emitting Devices
| Autor: | Po-Ching Kao, 高柏青 |
|---|---|
| Rok vydání: | 2007 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 Organic light-emitting diodes (OLEDs) are currently considered as promising candidates for large-area, full-color and flat-panel displays due to their prominent advantages such as ease in fabrication, faster switching speed, higher contrast, lighter, thinner and convenience of use in applications. A lot of effort has, therefore, been made to improve device structures and to understand their operating mechanisms. In this research, first, we systematically investigated the physical characteristics of the various metal-phthalocyanines (MPcs) and the influence of the MPcs hole-injection layer (HIL) on the EL performance of ITO/MPc/NPB/Alq3/LiF/Al devices. The characteristics were measured at room temperature with a thickness variation of the MPc layer. The results showed that the individual molecular orbital (HOMO and LUMO) level energies of MPcs are dependent on their central metal atoms. The turn-on voltage for the devices is lowered by inserting MPc layers. In addition, the turn-on voltage decreases significantly with the increase of the HOMO levels of the MPc films, which demonstrates that the MPc/NPB interface instead of the ITO/MPc interface plays an important role in the hole-injection. Second, we describe the phosphorescent characteristics of a new red-emitting iridium complex, bis(2-Naphthalen-1-yl-5-trifluoromethyl-pyridine-N,C2΄)iridium(III) acetylacetonate [(5-fnapy)2Ir(acac)], together with investigating the electroluminescence (EL) mechanisms of organic light-emitting diodes (OLEDs) by using this complex as a red dopant. A bright red and white light emission with CIE coordinates (0.65, 0.34) and (0.33, 0.32) can be realized using the ITO/NPB/CBP:(5-fnapy)2Ir(acac)/BAlq3/LiF/Al structure with different the properly doping concentrations of (5-fnapy)2Ir(acac) in CBP host. The white-emission spectrum of this device is composed of a red band from (5-fnapy)2Ir(acac) and two blue emissions from NPB and BAlq3. The CIE coordinates were well within the white zone when applied voltage is varied from 9 V to 18 V. Third, we fabricate large-scaled patterned organic light-emitting devices with ITO/NPB/ Alq3/LiF/Al structure on flexible polyethylene terephthalate (PET) substrates using two patterning techniques. One is a low-pressure imprinting lithography and the other is a combination of roller-type imprinting lithography and photolithography (CRIP). The patterns of the pixel array were defined in crossed-strip style with indium tin oxide (ITO) anode patterned by lithography techniques followed by wet chemical etching and cathode strips deposited using metal mask. Due to the PET substrate is thin and flexible, it could decrease the pressure needed for high yield pattern transfer as compared to that required with rigid substrate. The optimal imprinting pressure and temperature are 3 kg/cm2 and 140°C, respectively. On the other hand, compared with conventional imprint lithography or photolithography, the CRIP technique has the advantages of better uniformity, less force, consuming less time, lower cost, and higher aspect ratio. The performances of these devices were comparable to that of devices patterned by conventional photolithography. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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