The Research of LiFAl Layer's Effects in Organic Light-Emitting-Diode
| Autor: | Huei-Fang Shiau, 蕭惠芳 |
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| Rok vydání: | 2002 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 90 Because of many advantages of Organic Light-Emitting Diode (OLED), for example : fast responsibility、high brightness、large view angle、light weight、flexible substrate and low cost, OLEDs have attracted increasing attention in display market in recent years. But the popular materials used as electron-transport layer and emitting material is Alq3 because of its high stability, it is needed to take low work-function metal as cathode to lower the barrier of electron-injection from cathode into the low electron affinity material, Alq3. The most common cathode is made of Mg0.9:Ag0.1 which has lower barrier height than Al. After the report of using LiFAl layer as an cathode by Kodak, there are several research reports have been proposed to find out the reasons that improve carrier injection from LiFAl cathode. In our structure, we took NPB as HTL and Alq3 as ETL and light emitting material. Inserting a thin layer of LiF (about 10Å) between the emission layer and the metal cathode could reduce the operation voltage and enhance light-emitting efficiency to about 3 times. The thickness of LiF would take an important influence in device performance. In our system, the optimized thickness is 8Å. By atomic force microscope, the surface of organic layer was not covered completely with LiF up to 20 Å, and there were several fine bubbles loosely appearing on the surface of LiFAl. These bubbles would be adsorbed by the underlying Alq3 after biasing.We deduces that the ability of LiFAl cathode to reduce operation voltage doesn’t only come from the Li atoms released from the chemical reaction between LiF and Al, but also come form the gas-adsorption by Alq3, which gas released form the chemical reaction of LiF and Al. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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