Photoreactive main chain conjugated polymer containing oxetane moieties in the side chain and its application to green electrophosphorescence devices

Abstract

The utilization of a photoreactive hole injection/transport layer in multilayer electrophosphorescence polymer light-emitting diodes (PLEDs) is demonstrated in this study. A new photoreactive polymer was synthesized using 3,6-dibromo-9-(6-((3-methyloxetan-3-yl)methoxy)hexyl)-9H-carbazole and 2,4-dimethyl-N,N-bis(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)aniline via the Suzuki coupling reaction. When oxetane groups were photopolymerized in the presence of a cationic photoinitiator, the cured film showed good compatibility with PEDOT:PSS and the indium tin oxide (ITO) layer due to the hydrophilic nature of the cross-linked section. The resulting green light-emitting device bearing PVK:PBD:Ir(Cz-ppy)(3) exhibits a maximum external quantum efficiency of 8.73%. corresponding to a luminous efficiency of 28.2 cd/A when using the device configuration of ITO/POx-TPACz/PEDOT:PSS/PVK:PBD:Ir(Cz-ppy)(3)/TAZ/Alq(3)/LiF/Al. These values are higher than those of PLEDs using conventional PEDOT:PSS as a single hole injection layer (HIL). The slight degree of improvement in device efficiency is due to the reduced hole injection barrier. (c) 2009 Elsevier B.V. All rights reserved.