Reactions of singlet excitons in tris-(8-hydroxyquinoline) aluminum

Singlet excited state reactions in thin films of tris(8-hydroxyquinoline) aluminum (Alq3), a well known emitter for organic electroluminescent devices, are described. Bimolecular recombination dominates the singlet exciton decay in pristine films at high intensities, thus decreasing the photoluminescence quantum efficiency and singlet lifetime. The measured rate constant of the singlet-singlet annihilation in Alq3 films is γss = (3.5±2.5) × 10−11 cm3 s−1. The value of the diffusion coefficient of singlet excitons estimated from γss is Ds = (1.2±0.8) × 10−5 cm2s−1.