Improving the Efficiency of AIEgen-Based Nondoped Blue Organic Light-Emitting Diode by Rational Isomer Engineering

The
development of efficient and stable blue emitters remains a
great challenge for organic light-emitting diodes (OLEDs). Herein,
a pair of tetraphenylbenzene (TPB)-based isomers of TPB-2AC and iTPB-2AC
featuring aggregation-induced emission characteristics are designed
and synthesized by attaching two diphenylamine (DPA) moieties and
two cyano (CN) groups on its peripheral vicinal or alternating phenyl
rings. The nondoped blue OLED with iTPB-2AC as emitting layer exhibits
a maximum external quantum efficiency (EQE) of 8.23% with a low operation
voltage of 2.8 V, and the performance of the device is comparable
with the reported nondoped blue OLEDs based on conventional fluorescent
emitters. Whereas, the TPB-2AC-based device shows a low efficiency
roll-off effect. Their horizontal dipole orientation and “hot
exciton” process were rationalized to play key roles for these
performance differences. This work provides a general strategy to
achieve high-performance nondoped blue OLED by rational isomer engineering.