A novel family of hole-transport polyurethanes (PUs) has been developed. The PUs were preparedfrom the condensation polymerization of isophorone diisocyanate (IPDI) with (
E,E)-1,4-bis(2-hydroxystyryl)benzene, an oligo
p-phenylene-(
E)-vinylene (OPV) unit, and various amounts of 2,5-bis(4-hydroxyphenyl)-1,3,4-oxadiazole (OXD), as well as with 4-
tert-butyl phenol as the terminal group. ThePUs demonstrates superior properties that were concluded on the basis of the improved current injectionin the corresponding hole-only device. The OLED device with the OPV-PU interfacial layer inserted inITO/PEDOT:PSS(20 nm)/PU(30 nm)/
-NPB(10 nm)/Bebq
2(20 nm)/Ca(10 nm)/Ag(100 nm) has a dramaticvoltage reduction of 2.5 V under the current density of 100 mA/cm
2. When compared to the controldevice, the current efficiency was improved 2.37 times. The maximum brightness increased to 14900cd/m
2 in comparison to that of 5780 cd/m
2 for the control device. The performance of the OLED deviceswas fine-tuned by adjusting the combination of the OPV and OXD units to reach electron-hole balancedconditions. The maximum current efficiency increased to 4.12 cd/A at 5.5 V when the PU layer of OPV:OXD = 67:33 was used.