Delayed Fluorescence by Triplet Excitons

Triplet excitons in aromatic molecules are still more effective energy conductors than singlet excitons. Their lifetimes are longer and their hopping times are not 

The existence of triplet excitons was first discovered through the observation of delayed fluorescence (Fig. 6.22). This is a particularly characteristic process for organic crystals. In this process, two triplet excitons can combine their energy and form a singlet exciton, according to the scheme Ti -i- Ti Si -i- Sq. 

---