Novel diarylborane–phenanthroimidazole hybrid bipolar host materials for high-performance red, yellow and green electrophosphorescent devices

Abstract

In this work, two novel bipolar host materials p-BPPI and m-BPPI containing phenanthroimidazole/dimesitylborane (Mes2B) with para- and meta-linkage have been designed, synthesized and characterized. The appending Mes2B moiety improves the thermal stability, electrochemical stability and carrier injection/transport ability of both target compounds. The test results of time-of-flight (TOF) and single-carrier devices show that both the new hosts possess bipolar charge-transporting characteristics. As a result, series of highly efficient green (66.3cdA−1, 63.1lmW−1, 18.2%), yellow (55.2cdA−1, 66.6lmW−1, 14.5%) and red (20.1cdA−1, 20.4lmW−1, 13.5%) PhOLEDs are achieved by using them as the universal host materials. The results indicate that bipolar host p-BPPI and m-BPPI have high potential in fabricating various color OLEDs for displays and lighting applications. Our study further enriches the selection of D and A group for phosphorescent host materials. The relationship between molecular structures and optoelectronic properties is discussed experimentally and theoretically.