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

Abstract

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(4hydroxyphenyl)-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)/R-NPB(10 nm)/Bebq 2 (20 nm)/Ca(10 nm)/Ag(100 nm) has a dramatic voltage reduction of 2.5 V under the current density of 100 mA/cm 2 . When compared to the control device, the current efficiency was improved 2.37 times. The maximum brightness increased to 14900 cd/m 2 in comparison to that of 5780 cd/m 2 for the control device. The performance of the OLED devices was fine-tuned by adjusting the combination of the OPV and OXD units to reach electron-hole balanced conditions. 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.

A Deep-Blue Electroluminescence from 2,5-Diphenyl-1,3,4-oxadiazole and Polyfluorene Copolymer End-capped with Triphenylamine

“…On this hypothesis, a possible strategy to suppress the undesirable electrochemical degradation is to control the transportation rates of hole and electrons for the hole/electron recombination at the emission layer central region apart from the electrode interfaces. For this purpose, we carried out the NOVEL OXADIAZOLE-MODIFIED END-CAPPED POLYFLUORENES 395 incorporation of oxadiazole unit possessing an electron-transporting character by copolymerization into the end-capped polyfluorene mentioned above to tune the total carrier transportation behavior [9,10]. Copolymerization is also expected to disturb undesirable molecular aggregation in the end-capped polyfluorene as an origin of a green emission, as triggered by Joule heat generation during device operation [11].…”

Electrochemical fluorescence switching properties of conjugated polymers composed of triphenylamine, fluorene, and cyclic urea moieties

“…In addition, PU conducting polymers have recently been developed59–61 and applications of PUs on PLED have been reported. For example, PUs can be used as effective hole‐transport matrix62–65 as well as applied for light emitting layers 66–68. Traditional methods for PU synthesis usually involve diamine and diisocyanate moieties, which are toxic reagents.…”

Emission Characteristics of Organic Light-Emitting Diodes and Organic Thin-Films with Planar and Corrugated Structures

“…Organic materials have attracted much attention for applications in electronic and optoelectronic devices, such as organic transistors, organic solar cells and organic light-emitting devices [ 1 – 4 ]. The organic light-emitting diode (OLED) is one of the most promising technologies for display and lighting applications [ 5 , 6 ].…”