Self-assembled tetraoctylammonium bromide as an electron-injection layer for cathode-independent high-efficiency polymer light-emitting diodes

Sung Nien Hsieh, Shih Wei Hsiao, Tsan Yao Chen, Chen Yan Li, Chih Hao Lee, Tzung Fang Guo, Yao Jane Hsu, Tsang Lang Lin, Yen Wei, Ten Chin Wen

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)

Abstract

Tetraoctylammonium bromide (TOAB), a general kind of quaternary ammonium salt, was spin-coated onto the surface of a green-emissive poly(9,9- dialkylfluorene) derivative (G-PF) to fabricate cathode-independent polymer light-emitting diodes (PLEDs). The electroluminescence efficiencies were 15.4, 11.4, and 9.1 cd A-1 for TOAB with Al, Ag, and Au as the cathode, respectively, which are better than that of the device with Ca/Al as the cathode (6.1 cd A-1). The molecular nanomorphologies of TOAB deposited on G-PF were investigated using synchrotron X-ray diffraction. Results show that TOAB molecules nucleated on the hydrophobic G-PF surface and self-assembled into a highly ordered lamellar structure during the spin-coating process. This unique structure produces suitable molecular dipoles between N+ and Br-, significantly improving the electron-injection ability from stable metals to G-PF. The direction of the molecular dipole between N + and Br- can be reversed by using a hydrophilic ZnO for producing an efficient electron injection layer in an inverted device. The self-assembled molecules of TOAB create an anisotropic dipole on hydrophilic or hydrophobic surfaces, making them a potentially efficient electron-injection layer.

Original languageEnglish
Pages (from-to)8715-8720
Number of pages6
JournalJournal of Materials Chemistry
Volume21
Issue number24
DOIs
Publication statusPublished - 2011 Jun 28

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • Materials Chemistry

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