In this work, two innovative bipolar host materials, TPA-BIP and Cz-BIP, were designed and synthesized based on benzimidazole-hybridized phenanthridine (BIP) moiety as the electron transport unit. Compared to the widely used electronic transport unit benzimidazole, the BIP unit possesses a large planar rigid structure that can effectively enhance the thermal stability and the electron transfer capability of materials. Both materials exhibit good thermal stability respectively with Tg of 113 oC and 141 oC, proper HOMO/LUMO energy levels, and balance carrier transport capabilities. The red phosphorescent organic light-emitting diode prepared based on both materials achieve relatively high luminescence efficiency and relatively low efficiency roll-off. In particular, the EQEmax of the R1 device using TPA-BIP as the host material reaches 21.5%, which is more superior than that of the conventional host material CBP (EQEmax of 9.84%). Even at 1000 cd/m2, the device still achieves an EQE of 21.3% with virtually no decrease. In conclusion, the results demonstrate the broad development potential of these BIP-based host materials for red PhOLEDs applications.