ENVIRONMENTAL STABILITY OF ALUMINUM TRIS(8-HYDROXYQUINOLINE) (ALQ(3))AND ITS IMPLICATIONS IN LIGHT-EMITTING DEVICES

The thermal stability of the aluminum tris(8-hydroxyquinoline) (Alq(3) ) is currently discussed, in light of its vital role in failure mechan isms of molecular-based light emitting diodes (LEDs). This was investi gated with the use of gas chromatography/mass spectroscopy (GC/MS), as sisted by a specialized accessory that permits heating of powders or t hin films of Alq(3) under a controlled environment. We have shown that at elevated temperatures, Alq(3) undergoes a ligand exchange reaction with water, which readily adsorbs on its surface. The increased sensi tivity of CC/MS in detecting the liberated 8-hydroxyquinoline (8-Hq) i ndicates that Alq(3) is extremely sensitive to the moisture above 90 d egrees C. The surface of a freshly sublimed Alq(3) powder or film beco mes saturated with water in less than 2 minutes, under normal laborato ry conditions. The implications of the underlying chemistry are discus sed in relation to failure mechanisms observed in Alq(3) based LEDs.