Studies on the intrinsic degradation of organic light-emitting devices (OLEDs) based on tris(8-hydroxyquinolinolato)aluminum (III) (Alq(3)) revealed that the operation stability of the OLEDs depends on the process pressure during device fabrication. Lowering of the pressure resulted in stable devices. In sharp contrast, differences in the initial device characteristics were marginal in all devices. Analyses with a quadrupole mass spectrometer indicated that the primary difference in the pressure during device fabrication was attributable to the amount of residual water. The results show that the degradation of OLEDs is associated with the electrochemical reaction of Alq(3) with water. (c) 2006 Elsevier B.V. All rights reserved.