Cascade hole transport in efficient green phosphorescent light-emitting devices achieved by layer-by-layer solution deposition using photocrosslinkable-conjugated polymers containing oxetane side-chain moieties

Jicheol Shin, Hyun Ah Um, Min Ju Cho, Tae Wan Lee, Kyung Hwan Kim, Jung Il Jin, Seogshin Kang, Taehan Park, Sung Hoon Joo, Joong Hwan Yang, Dong Hoon Choi

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3 Citations (Scopus)

Abstract

A hole-injection/transport bilayer structure on an indium tin oxide (ITO) layer was fabricated using two photocrosslinkable polymers with different molecular energy levels. Two photoreactive polymers were synthesized using 2,7-(or 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 a Suzuki coupling reaction. When the oxetane groups were photopolymerized in the presence of a cationic photoinitiator, the photocured film showed good solvent resistance and compatibility with a poly(N-vinylcarbazole) (PVK)-based emitting layer. Without the use of a conventional hole injection layer (HIL) of poly(3,4-ethylenedioxythiophene)/ (polystyrenesulfonate) (PEDOT:PSS), the resulting green light-emitting device bearing PVK: 5-4-tert-butylphenyl-1,3,4-oxadiazole (PBD):Ir(Cz-ppy)3 exhibited a maximum external quantum efficiency of 9.69%; this corresponds to a luminous efficiency of 29.57 cd/A for the device K-4 configuration ITO/POx-I/POx-II/PVK: PBD:Ir(Cz-ppy)3/triazole/Alq3/LiF/Al. These values are much higher than those of PLEDs using conventional PEDOT:PSS as a single HIL. The significant improvement in device efficiency is the result of suppression of the hole injection/transport properties through double-layered photocrosslinked- conjugated polymers.

Original languageEnglish
Pages (from-to)388-399
Number of pages12
JournalJournal of Polymer Science, Part A: Polymer Chemistry
Volume50
Issue number2
DOIs
Publication statusPublished - 2012 Jan 15

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Keywords

  • conjugated polymers
  • electrophosphorescence
  • hole transport layer
  • iridium(III) complex
  • light-emitting diodes (LED)
  • luminescence
  • oxetane
  • photocrosslink
  • photoluminescence
  • photopolymerization
  • solubility
  • synthesis

ASJC Scopus subject areas

  • Materials Chemistry
  • Polymers and Plastics
  • Organic Chemistry

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