TY - JOUR
T1 - Optical and ESR studies of Tris(8-hydroxyquinoline)aluminum
AU - Roy, V. A.L.
AU - Pode, R. B.
AU - Rao, T. K.Gundu
AU - Djurišić, A. B.
AU - Baldacchini, G.
N1 - Funding Information:
The authors wish to thank T. Baldacchini (Chemistry Department, Boston College, USA) for useful discussions and suggestions during the last stages of this work. This work is partly supported by the seed funding grant of the University of Hong Kong.
PY - 2004/1/15
Y1 - 2004/1/15
N2 - Tris(8-hydroxyquinoline)aluminum (AlQ) powder has been characterized using photoluminescence and electron spin resonance (ESR). The broad asymmetric excitation band is centered at ∼425nm, while the emission band centered at ∼505nm is similar to those reported in films. A significant ESR signal with a linewidth of 10G and g-value of 2.0038 has been observed in as synthesized AlQ powder at room temperature. The signal at same position is present in AlQ powder as-received from Aldrich, as synthesized AlQ powder, and AlQ powder purified by vacuum sublimation. The appearance of the ESR signal is attributed to organic free radicals. Moreover, exposure of AlQ powder to humid air enhances the ESR signal intensity which increases linearly with exposure duration. This is in agreement with recently proposed degradation mechanism in AlQ based organic light emitting diodes, where degradation was attributed to unstable cationic AlQ species. The discovery of natural free radicals in freshly synthesized AlQ may be useful to prevent the degradation of AlQ and other analogous compounds in organic light emitting diodes (OLEDs).
AB - Tris(8-hydroxyquinoline)aluminum (AlQ) powder has been characterized using photoluminescence and electron spin resonance (ESR). The broad asymmetric excitation band is centered at ∼425nm, while the emission band centered at ∼505nm is similar to those reported in films. A significant ESR signal with a linewidth of 10G and g-value of 2.0038 has been observed in as synthesized AlQ powder at room temperature. The signal at same position is present in AlQ powder as-received from Aldrich, as synthesized AlQ powder, and AlQ powder purified by vacuum sublimation. The appearance of the ESR signal is attributed to organic free radicals. Moreover, exposure of AlQ powder to humid air enhances the ESR signal intensity which increases linearly with exposure duration. This is in agreement with recently proposed degradation mechanism in AlQ based organic light emitting diodes, where degradation was attributed to unstable cationic AlQ species. The discovery of natural free radicals in freshly synthesized AlQ may be useful to prevent the degradation of AlQ and other analogous compounds in organic light emitting diodes (OLEDs).
KW - ESR
KW - Stability
KW - Tris-(8-hydroxyquinoline)aluminum (AlQ)
UR - http://www.scopus.com/inward/record.url?scp=0344014305&partnerID=8YFLogxK
U2 - 10.1016/j.mseb.2003.09.017
DO - 10.1016/j.mseb.2003.09.017
M3 - Article
AN - SCOPUS:0344014305
SN - 0921-5107
VL - 106
SP - 85
EP - 88
JO - Materials Science and Engineering B: Solid-State Materials for Advanced Technology
JF - Materials Science and Engineering B: Solid-State Materials for Advanced Technology
IS - 1
ER -