High-Performance Hole-Transport Polyurethanes for Light-Emitting Diodes Applications

A novel family of hole-transport polyurethanes (PUs) has been developed. The PUs were prepared from 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. The PUs demonstrates superior properties that were concluded on the basis of the improved current injection in the corresponding hole-only device. The OLED device with the OPV−PU interfacial layer inserted in ITO/PEDOT:PSS(20 nm)/PU(30 nm)/α-NPB(10 nm)/Bebq2(20 nm)/Ca(10 nm)/Ag(100 nm) has a dramatic voltage reduction of 2.5 V under the current density of 100 mA/cm2. When compared to the control device, the current efficiency was improved 2.37 times. The maximum brightness increased to 14900 cd/m2 in comparison to that of 5780 cd/m2 for the control device. The performance of the OLED devices was fine-tuned by adjusting the co...