Poly(ethylene oxide)-functionalized Al cathodes of tunable electron-injection capabilities for efficient polymer light-emitting diodes

Ming Wei Lin, Ten-Chin Wen, Yao Jane Hsu, Tzung-Fang Guo

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Poly(ethylene oxide)-functionalized aluminum (Al) cathodes of tunable electron-injection capabilities are reported in this study for the fabrication of high-performance polymer light-emitting diodes (PLEDs). The composite cathodes are prepared by thermally co-evaporating poly(ethylene glycol) dimethyl ether (PEGDE, Mnca. 2000) polymer with Al metal simultaneously in vacuum as the cathode buffer. We attribute the formation of the carbide-like/Al complex as characterized by X-ray photoelectron spectroscopy (XPS) to the instant chemical reactions between the ethylene oxide functional groups with Al, which markedly enhances the device performance. The electron-injection capabilities of PEGDE:Al/Al cathodes are correlated with the contents of the carbide-like/Al complex in the buffer layer and can, therefore, be modulated by varying the co-evaporation ratios of PEGDE and Al. The luminous efficiency of green polyfluorene-based PLEDs applying an PEGDE:Al (2:1)/Al cathode is of 10.46 cd A-1, which is much higher than that of ∼0.04, 5.19, 6.40 cd A-1 for PLEDs with Al, PEGDE/Al and calcium/Al cathodes, respectively. This research leads to an alternative cathode design, free of salts, additives, complicated synthesis, and of tunable electron-injection capabilities to balance the opposite charge carriers for fabricating high-performance PLEDs.

Original languageEnglish
Pages (from-to)18840-18846
Number of pages7
JournalJournal of Materials Chemistry
Volume21
Issue number46
DOIs
Publication statusPublished - 2011 Dec 14

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Chemistry

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