REACTIONS OF SINGLET EXCITONS IN TRIS-(8-HYDROXYQUINOLINE) ALUMINUM

Singlet excited state reactions in thin films of tris(8-hydroxyquinoli ne) aluminum (Alq(3)), a well known emitter for organic eledroluminesc ent devices, are described. Bimolecular recombination dominates the si nglet exciton decay in pristine films at high intensities, thus decrea sing the photoluminescence quantum efficiency and singlet lifetime. Th e measured rate constant of the singlet-singlet annihilation in Alq(3) films is gamma(SS) = (3.5+/-2.5) X 10(-11) cm(3) s(-1). The value of the diffusion coefficient of singlet excitons estimated from gamma(SS) is D-S = (1.2+/-0.8) X 10(-5) cm(2) s(-1).