Oxygen quenching of delayed fluorescence in the solid state

A gradual increase in delayed fluorescence intensity is observed in crystalline 2-chloroanthracene and 9,10-diphenylanthracene in air under irradiation with light of constant intensity in the first triplet band. Detailed measurements in 2-chloroanthracene of delayed fluorescence intensity and triplet exciton lifetime show that the behavior is consistent with a triplet exciton-oxygen interaction which results in a depletion of the ground-state molecular oxygen concentration in the lattice and leads to a time dependence of the triplet exciton lifetime and of the effective S₀ → T₁ absorption coefficient of the material.