Face-to-face order-packed mode promotes thermally activated delayed fluorescence to achieve stronger aggregation-induced emission

Abstract

Two novel aggregation-induced delayed fluorescence materials (AIDF) FCP-BP-PXZ [9- (4-Fluorophenyl) -9H-carbazole-3-yl] [4- (10H-phenoxazine-10-yl) phenyl] methane and FCP-BP-PTZ [9- (4-Fluorophenyl) -9H-carbazole-3-yl] [4- (10H-penzothiazin-10-yl) phenyl] methane were synthesized. Experiments and molecular dynamics (MD) simulations revealed that FCP-BP-PXZ exhibits orderly face-to-face arrangement stacking mode, which inhibits non-radiation inactivation channel and reduces energy loss by restricting larger vibration and rotation of the molecule due to abundant intermolecular hydrogen bonds and strong intermolecular π-π interactions. FCP-BP-PTZ's performance was hampered by erratic relaxation aggregation. The maximal external quantum efficiency (EQEmax) of non-doped and doped organic light-emitting diodes (OLEDs) constructed on FCP-BP-PXZ was 11.2% and 18.2%, respectively. Furthermore, at a brightness of 1000 cd m−2, non-doped and doped devices had a low turn-on voltage of 3.0–3.5 V, with 2.0% and 3.3% efficiency roll-off, owing to the microsecond-scale delayed lifetime. The FCP-BP-PXZ-based non-doped device, in particular, achieved a brightness of 62,390 cd m−2, which was crucial in non-doped yellow OLEDs.

Keywords

• Thermally activated delayed fluorescence
• Face-to-face order-packed
• Aggregation-induced emission