Engineering high-brightness and long-lived organic room-temperature phosphorescence via systematic molecular design.

We report a systematic molecular design in BF2bdk-based afterglow emitters with photoluminescence quantum yields up to 46.3% and lifetimes around 1 s. Suitable excited-state types, diverse excited state species, relatively small singlet-triplet energy gaps and strong dipole-dipole interactions are critical in determining the afterglow properties.