PLED devices containing triphenylamine-derived polyurethanes as hole-transporting layers exhibit high current efficiencies

hydroxyphenyl)carbazole) (Cz) can be linked through isophorone diisocyanate (IPDI) bridges and incorporated as hole-transporting layers in high-performance PLED devices. The TPA-IPDI-Cz type of polyurethane (PU) materials (P1-P5) showed superb hole injection and transport properties based on the results of the hole-only-device study. We prepared the devices in two kinds of configuration: system (1) Indium Tin Oxide (ITO)/PU (20 nm)/{Iridium(III) bis(2-phenylpyridine), (Ir(ppy)3) + 2-(4- biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (t-PBD) + polyvinylcarbazole (PVK)) (50 nm)/Mg (10 nm)/Ag (100 nm), for the device with P1 (DP1), the brightness increased to 14 000 cd m 2, the current efficiency rose to 13.4 cd A 1, and the turn-on voltage was reduced to 21 V (at 100 cd m 2). In system (2) ITO/PEDOT-PSS (30 nm)/PU (20 nm)/(Ir(ppy)3 + t-PBD + PVK) (50 nm)/Mg (10 nm)/Ag (100 nm), with PEDOT-PSS as the hole-injection layer, was compared to the standard device (S2) having the configuration ITO/PEDOT-PSS (50 nm)/(Ir(ppy)3 + t-PBD + PVK) (50 nm)/Mg (10 nm)/ Ag (100 nm); the brightness of the double layer device with P5 (DDP5) increased to 12 500 cd m 2 and the current efficiency dramatically rose to 34.7 cd A 1, compared with values of 6250 cd m 2 and 21.8 cd A 1, respectively, for S2.