Analysis of N-type Doping Organic Light Emitting Devices by Using Admittance Spectroscopy

• Main Authors: Ming-ChiLi, 李明錡
• Other Authors: Sheng-Yuan Chu
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/56908714417840858873

碩士 === 國立成功大學 === 電機工程學系 === 103 === In this thesis, an n-type OLED with Rb2CO3 doped in MADN as electron transporting layer (ETL) is investigated. The equivalent circuit model of electron-only devices with incorporation of Rb2CO3 into MADN as ETL are successfully developed by applying temperature-dependence admittance spectroscopy measurement (ASM). Frequency response of the ETL is affected by environmental temperature, and the shifting of G/F peak can obtain activation energy. Fermi level will shift more toward vacuum level with the increasing of Rb2CO3 doping percentage, leading to decreased equivalent resistance of ETL, reduced electron injection barrier, and improved conductivity. Thus the maximum luminance of electroluminescent device enhanced from 15530 to 26694 cd/m2, the maximum luminance efficiency raised from 3.9 to 5.1 cd/A, and the operation voltage at 100 cd/m2 decreased from 5.4 to 4.2 V when 25% Rb2CO3 is doped into MADN as ETL. Meanwhile, if the Rb2CO3 doping concentration is exceed 25%, it would be too high to make the electron hard to inject to emitting layer, resulting in device decay. In addition, some significant physics parameters of organic materials such as parallel resistance, density of state, and carrier concentration are cable to be obtained via proper math models. It is useful for device researches and material analysis. Keywords：OLED、n-type doping、admittance spectroscopy、activation energy