Thermally activated delayed fluorescence with a narrow emission spectrum and organic room temperature phosphorescence by controlling spin–orbit coupling and phosphorescence lifetime of metal-free organic molecules

This work presents a study of two organic molecules with a very similar, large singlet-triplet energy gap, one of which is a thermally activated delayed fluorescence (TADF) emitter and the other is a room temperature phosphorescence (RTP) emitter. By investigating their photophysical properties we are able to explain their distinct behavior. The molecules are studied in non-polar polymers and OLED hosts. Furthermore, this work presents a CT TADF emitter that shows a narrow and resolved electroluminescence spectrum (FWHM = 53 nm). The study shows an efficient RTP emitter based on a D-D-D structure and also the first acridone-based TADF emitter with a D-A-D structure.