Design, synthesis, photophysical, and electrochemical properties of DCM-based conjugated polymers for light-emitting devices

Mahalingam Vanjinathan, Hong-Cheu Lin, A. Sultan Nasar*

*Corresponding author for this work

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

A series of conjugated hyperbranched polymers, hyperbranched copolymers, and linear polymers containing 2-pyran-4-ylidenemalononitrile (acceptor) and triphenylamine/fluorene (donor) units were synthesized and characterized by FTIR, 1H NMR, thermogravimetric analyses, differential scanning calorimetry, gel permeation chromatography, UV-visible, photoluminescence, and cyclic voltammetry measurements. All the polymers show red-light emission in the range of 566-656 nm both in solution and in solid state. The quantum efficiency of the polymers was in the range of 56-82%. Among the six polymers synthesized, only polymers containing fluorene units show T g and polymers based on triphenylamine not exhibit T g. The band gap of these polymers were found to be reasonably low; hyperbranched copolymer containing fluorene unit shows lowest band gap of 2.18 eV due to the stabilization of LUMO energy level by the electron withdrawing -CN groups. The thermal and solubility behavior of the polymers were found to be good. All the EL spectra of the devices (indium-tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/ polymer/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline/tris(8-hydroxyquinoline) aluminum)/LiF/Al) show red-light emission, and the device fabricated with P3 and P4 shows maximum luminance and luminous efficiency of 4104 cd m -2 and 0.55 cd Å -1 and 3696 cd m -2 and 0.47 cd Å -1, respectively, indicates that they had the best carrier balance.

Original languageEnglish
Pages (from-to)3806-3818
Number of pages13
JournalJournal of Polymer Science, Part A: Polymer Chemistry
Volume50
Issue number18
DOIs
StatePublished - 15 Sep 2012

Keywords

  • A + B approach
  • charge transfer
  • conjugated polymers
  • cyclic voltammetry
  • electroluminescence
  • hyperbranched polymers
  • Knoevenagel reaction
  • photophysical property
  • PLEDs

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