Study on the Al/LiF interfaces of the organic light-emitting diodes

• Main Authors: Yuan-liang Liu, 劉原良
• Other Authors: Uerng-Yih Ueng
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/73708401267128058057

碩士 === 國立中山大學 === 電機工程學系研究所 === 92 === In this present paper, the electrical characteristics of the interface between the cathode and organic layer in OLEDs are discussed. The dipole formed between the cathode and organic layer are the dominant factor resulting in the electrical characteristics of OLEDs. However, based on the Al/LiF/Alq3 architecture published by the Kodak company, it is mainly because that by inserting a LiF layer lead to change the interface characteristic of Al/Alq3 as to changed the chemical reaction occurred at the interface of Al/Alq3. The LiF interlayer could enable the contact interface being depolarized and the work function being close to the vacuum level, therefore, it will reduce the electron injection barrier to improve the OLED performance. In addition, the increase luminous efficiency was due to that without generating any gap state and interdiffusion occur at the interface of Al/LiF/Alq3. For the carrier injection model reported by several authors, the carrier injection process is summarized by two steps as follow: first, the inject carriers translate from metal Fermi level to the energy distribution of interface. Second, inject carriers translate from the energy distribution of interface to the energy distribution of organic layer, afterward, the inject carriers migrate with hopping conduction in the organic level. Hence, it will regards to the dependence of the variety of LiF thickness on the influence of the injection model, and assume that as LiF thickness is 0.5 nm the device could be able to have the best performance, and also assume that LiF was able to decompose equal number of Alq3- and the Li+ ions at the interface of Al/LiF/Alq3 contact, and that led to form a voltage in the LiF layer. Finally, we found that the simulation approaches were consistent with the experimental results very well.