Phosphorescence

Phosphorescence materials are frequently used to increase the quantum efficiency of materials since the radiative decay from both the triplet and singlet states contributes to the light emission. Since typically the lifetime of phosphorescence is long, thermal deactivation occurs by oxygen quenching, solvent movement, and intermolecular collision and the phosphorescence cannot be observed at room temperature. The sample is therefore cooled and frozen at liquid nitrogen temperature to slow down the relaxation process.