Photooxidation effects on picosecond photoluminescence and photoconductivity in tris-(8-hydroxyquinoline) aluminum (Alq3).

The photogeneration of radiative excited states and charge carriers in pristine and photooxidized tris-(8-hydroxyquinoline) aluminum (Alq(3)) was studied by measuring both its photoluminescence and photoconductive response simultaneously, with subnanosecond resolution. 25 psec laser pulses at 355nm were used for excitation of vacuum evaporated 2-4 mu m thick films of Alq(3). We observed that photooxidation of Alq(3) with oxygen and UV Light substantially decreases the fluorescence lifetime and quantum yield as well as the photoconductive response. This decrease is shown to be a result of quenching of singlet molecular excitations by products of photooxidation of Alq(3).