Improvement in the Environmental Stability of Tris(8-hydroxyquinoline) Aluminum by Substitution of Sulphonic Acid in 8-hydroxyquinoline Ligand

Roy, V.A.L. , Kwong, C.Y., Djurišić, A.B., Pode, R.B., Gundu Rao, T.K. and Chan, W.K. (2004) Improvement in the Environmental Stability of Tris(8-hydroxyquinoline) Aluminum by Substitution of Sulphonic Acid in 8-hydroxyquinoline Ligand. In: Optical Science and Technology, SPIE's 48th Annual Meeting, San Diego, CA, USA, 03-08 Aug 2003, pp. 283-290. (doi: 10.1117/12.503009)

Abstract

Tris (8-hydroxyquinoline) aluminum (Alq3) is a commonly used electron transporting and/or light emitting material in organic light emitting diodes (OLEDs). However, it is well known that Alq3 is very sensitive to atmosphere exposure and that photoluminescence of Alq3 films decreases with the time of atmosphere exposure. Degradation is also a serious problem in Alq3 based OLEDs. Several degradation mechanisms have been identified in these devices, including formation of unstable cationic species due to passage of holes. Therefore, there is lots of interest in improving the stability of Alq3. We have synthesized Tris (8-hydroxyquinoline-5 sulphonic acid) aluminum [Al(qS)3] in order to improve the stability. We performed electron spin resonance measurements on Alq3 and Al(qS)3 powders. Unlike Alq3 which exhibited strong ESR signal, Al(qS)3 produced no detectable ESR signal indicating absence of free radicals in this material. To test the environmental stability of Al(qS)3 films, we have performed photoluminescence (PL) measurements in humid air at different temperatures and found that Al(qS)3 exhibits improved stability. After comparing the stability of Alq3 and Al(qS)3 thin films, fabrication of the light emitting diodes with Al(qS)3 emitting layer was attempted in order to compare the performance with Alq3 based devices.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Vellaisamy, Professor Roy
• Authors: Roy, V.A.L., Kwong, C.Y., Djurišić, A.B., Pode, R.B., Gundu Rao, T.K., and Chan, W.K.
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• ISSN: 0277-786X