Improvement in the environmental stability of tris(8-hydroxyquinoline) aluminum by substitution of sulphonic acid in 8-hydroxyquinoline ligand

V. Arul Lenus Roy; Chung Yin Kwong; Aleksandra B. Djurisic; Ramachandra B. Pode; T. K. Gundu Rao; Wai Kin Chan

doi:10.1117/12.503009

16 February 2004 Improvement in the environmental stability of tris(8-hydroxyquinoline) aluminum by substitution of sulphonic acid in 8-hydroxyquinoline ligand

V. Arul Lenus Roy, Chung Yin Kwong, Aleksandra B. Djurisic, Ramachandra B. Pode, T. K. Gundu Rao, Wai Kin Chan

Author Affiliations +

Proceedings Volume 5214, Organic Light-Emitting Materials and Devices VII; (2004) https://doi.org/10.1117/12.503009
Event: Optical Science and Technology, SPIE's 48th Annual Meeting, 2003, San Diego, California, United States

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.

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V. Arul Lenus Roy, Chung Yin Kwong, Aleksandra B. Djurisic, Ramachandra B. Pode, T. K. Gundu Rao, and Wai Kin Chan "Improvement in the environmental stability of tris(8-hydroxyquinoline) aluminum by substitution of sulphonic acid in 8-hydroxyquinoline ligand", Proc. SPIE 5214, Organic Light-Emitting Materials and Devices VII, (16 February 2004); https://doi.org/10.1117/12.503009

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