Enhancing the luminous efficiency of organic light emitting diodes using an n-type electron transporting layer

• Main Authors: Tsang-Wei Kuo, 郭倉維
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/79815460532290761608

碩士 === 義守大學 === 電子工程學系碩士班 === 98 === This study elucidates the optoelectronic properties of organic light-emitting diodes (OLEDs) with cesium iodide (CsI)-doped tris(8-hydroxyquinoline) aluminum (Alq3) as an n-type electron transporting layer (n-ETL). The device structure is glass/ITO/ m-MTDATA(10nm)/ NPB(30nm)/ Alq3(30nm)/ Alq3:CsI(x%, 15nm)/ Al(120nm). The driving voltage of an OLED gradually reduced with the increased content of CsI in an n-type ETL. The luminous efficiency of an OLED with a 5% CsI-doped Alq3 ETL is enhanced to 5.27cd/A, which is double of the un-doped device. Moreover, various physical and chemical analyses of CsI-doped Alq3 film are used to explore the reasons for improving device’s characteristics. The UV-Vis absorption spectrum of the Alq3:CsI film shows additional absorption peaks at around 450nm wavelengths. The phenomenon is speculated from the formation of CsI+- Alq3- charge transfer complex. The analysis of electron spectroscopy (x-ray photoelectron spectroscopy) on Cs element reveals the occurrence of chemical shift phenomenon. Atomic force microscopy (AFM) is used to analyze the surface roughness of CsI-doped Alq3 film with various doping concentration. An n-type ETL is one of the important factors to enhancing the optoelectronic properties of the OLEDs.