Constructing high-efficiency aggregation-induced delayed fluorescence molecules and OLEDs applying C-H···N hydrogen bond manipulation strategy

Thermally activated delayed fluorescent materials with aggregation-induced emission (AIE) feature have shown great potential applications in organic light-emitting diodes (OLEDs). In this work, three donor-acceptor molecules including PM-DMSFAC, Trz-DMSFAC, and PYPM-DMSFAC were constructed using dimethyl spiro-fluorene acridine as electron donor, while pyrimidine, triazine, and pyrimidine-pyridine hybrid groups with multiple C–H···N hydrogen bonds were respectively chosen as the acceptor units. There is a large dihedral angle between donor and acceptor, which facilitates the three molecules with efficient reverse intersystem crossing, and meanwhile the large steric hindrance endows them with AIE property. In comparison with PM-DMSFAC, an extra nitrogen atom is added in Trz-DMSFAC and PYPM-DMSFAC, making them more electronegative and exhibiting more intramolecular and intermolecular C–H···N interactions, which result in more stable molecular structures and higher PLQYs. When adopted to construct OLEDs, Trz-DMSFAC and PYPM-DMSFAC devices exhibit significantly improved efficiency. Importantly, Trz-DMSFAC afforded the best device performances with a maximum external quantum efficiency of 21.7% for non-doped OLED and 32.6% for doped device.