High-Performance Hole-Transport Polyurethanes for Light-Emitting Diodes Applications
Resource
Chemistry of Materials 18 (17): 4121-4129
Journal
Chemistry of Materials
Journal Volume
18
Journal Issue
17
Pages
4121 - 4129
Date Issued
2006
Date
2006
Author(s)
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(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 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. © 2006 American Chemical Society.
Other Subjects
Condensation; Current density; Light emitting diodes; Polymerization; Synthesis (chemical); Brightness; Current efficiency; Isophorone diisocyanate (IPDI); Voltage reduction; Polyurethanes
Type
journal article
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