Multi-functional highly efficient bipolar 9,9-dimethyl-9,10-dihydroacridine/imidazole-based materials for solution-processed organic light-emitting diode applications

A new class of bipolar compounds were designed and synthesized based on 9,9-dimethyl-9,10-dihydroacridine and phenylphenanthroimadazole/triphenylimadazole derivatives with different linking positions. Their thermal, photophysical, electrochemical properties and device characteristics were investigated. All four compounds were fabricated as emitters in solution-processed nondoped OLEDs. In particular, the N-phenylacridine 1,4-phenylene linked N-phenylphenanthrimidazole analogue displayed high efficiency with a maximum current efficiency (CE_max) of 4.6 cd A^─1 and a maximum external quantum efficiency (EQE_max) of 5.1% at CIE coordinates of (0.15, 0.09), which is very close to the NTSC blue standard. In addition, when the N-phenylacridine 1,3-phenylene linked triphenylimidazole analogue was used as a host for green phosphor Ir(mppy)₃ shows an impressive device performance with a CE_max of 62.7 cd A^─1 and a EQE_max of 18.9%. To the best of our knowledge, both results are the best efficiencies as emitter and host for solution-processed nondoped deep-blue OLEDs and green PhOLEDs, respectively.