We have investigated the physical and chemical characteristics of 8-hydroxyquinoline aluminium-(Alq

3

)

which has been used most widely as the electron transporting and emitting layer in organic light-emitting diodes.The fluorescent stability of Alq

3

is reported when the film was irradiated by an ultraviolet(UV)lamp.Thin film was analyzed in situ by using UV-V is absorption spectrophotometer

fluorescence spectrometer

X-ray photoelectron spectroscopy(XPS)and nano-second fluorescence spectrophotometer.We observed that the PL intensities and absorbance decreased with increasing the irradiated times

the fluorescent decays were rapid after irradiation

and the X-ray photoemission spectra of the irradiated films changed.Degradation in photoluminescence properties was significant in the presence of atmospheric moisture.The photodegradation reaction was a hydrisis process involving water in air to yield the fluorescent quenchers.The results indicated that reaction between H

2

O in the air and Alq

3

to liberate one or more 8-hydroxyquinoline at first and then undergoes a condensation reaction to generate a non-emissive compound

which plays a role as luminescence quenching center.The photodagradation of Alq

3

may seriously effect on the performance of LEDs.Therefore

it is important to keep the devices from the moisture in air for protection photodegradation

resulting in enhancement of the LEDs.