We have investigated the electrical properties of red organic light-emitting diodes (OLEDs) featuring a conventional structure comprising N,N¡¦-bis-(1-naphthl)-diphenyl -1,1¡¦- biphenyl-4,4¡¦-diamine (NPB) as the hole transporting layer (HTL) and 8-hydroxy -quinoline aluminum (Alq3) as the electron transporting layer (ETL). There are many methods for improving the efficiency of OLED with a configuration of ITO/NPB/Alq3/LiF/Al, such as increasing electron mobility of Alq3 or decreasing hole mobility of NPB. We can¡¦t obtain such improvement of the efficiency in the OLEDs composing Alq3:DCJTB as the emitting layer. From the measurement of hole-only and electron-only devices, the electrical characteristics such as hole concentration is greatly changed after doped DCJTB to Alq3 as the emitting layer. In our study, we also found that the efficiency increased upon the decreasing the deposition rate of NPB, presumably because the improved packing of NPB enhanced the carrier mobility, which therefore improve the carrier recombination rate. We deduced that the emitting layer of the device will become electron rich when the Alq3 is doped by DCJTB. It means that if we want to improve the efficiency of the red OLED, with Alq3:DCJTB as the emitting layer, we have to increase the hole concentration in the device. A red OLED device having the configuration of ITO/NPB/Alq3/LiF/Al exhibited a current efficiency of 7.4 cd/A at 20 mA/cm2 with Commission International de l'Eclairage coordinates of (0.62, 0.38). The current efficiency reached to 10.8 cd/A by putting optical film, which is a 50% improvement.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0812110-111312 |
| Date | 12 August 2010 |
| Creators | Lee, Kuen-lin |
| Contributors | Chih-Chien Lee, Yu-Kai Han, Shun-Wei Liu, Wen-Yao Huang, Mei-Ying Chang, Ping-Tsung Huang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0812110-111312 |
| Rights | not_available, Copyright information available at source archive |
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