Carbazole/Triphenylamine-Cyanobenzimidazole Hybrid Bipolar Host Materials For Green Phosphorescent Organic Light-Emitting Diodes

With a view to attain balanced charge flux for higher device performance of PhOLEDs, we have used carbazole/ triphenyl amine as hole transporting moiety and cyano along with benzimidazole as electron transporting core in 3-Cbz-ImdCN, 4-Cbz-ImdCN and TPA-ImdCN. Their thermal, photophysical and electrochemical properties have been evaluated to shed light on structure-property-performance relationship. Good performances have been exhibited by these bipolar host materials in green PhOLEDs with maximum external quantum efficiencies were observed in the range of 5.3?11.5% using Ir(ppy)3 emitter. Further, 3-Cbz-ImdCN hosted orange and red PhOLEDs with the Ir(MDQ)2acac and Ir(piq)2acac emitters revealed the external quantum efficiencies of 5.1% and 6.3%, respectively. In all the devices pure emission was observed from dopants only which clearly implies that the devices possess effective energy transfer from the host to the guest.