HUMIDITY-INDUCED CRYSTALLIZATION OF TRIS (8-HYDROXYQUINOLINE) ALUMINUM LAYERS IN ORGANIC LIGHT-EMITTING DEVICES

We report electroluminescence degradation studies of tris (8-hydroxyqu inoline) aluminum (Alq(3)) organic light-emitting devices (OLEDs) unde r ambient conditions. Alq(3) films and organic bilayer anode/naphthyl- substituted benzidine derivative/Alq(3)/cathode devices are studied vi a electroluminescence, photoluminescence, polarization microscopy and atomic force microscopy, and via microscopic infrared spectroscopy. Re sults reveal that humidity induces the formation of crystalline Alq(3) structures in originally amorphous films. The same phenomenon is foun d to occur in OLEDs and causes cathode delamination at the Alq(3)/cath ode interface that results in the formation of black (nonemissive) spo ts in the devices. (C) 1998 American Institute of Physics.