Self-assembled electroactive phosphonic acids on ITO : Maximizing hole-injection in polymer light-emitting diodes

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal

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Author(s)

  • Julie A. Bardecker
  • Hong Ma
  • Taedong Kim
  • Fei Huang
  • Michelle S. Liu
  • Yen-Ju Cheng
  • Guy Ting

Detail(s)

Original languageEnglish
Pages (from-to)3964-3971
Journal / PublicationAdvanced Functional Materials
Volume18
Issue number24
Publication statusPublished - 22 Dec 2008
Externally publishedYes

Abstract

In order to fulfill the promise of organic electronic devices, performance-limiting factors, such as the energetic discontinuity of the material interfaces, must be overcome. Here, improved performance of polymer light-emitting diodes (PLEDs) is demonstrated using self-assembled monolayers (SAMs) of triarylamine-based hole-transporting molecules with phosphonic acid-binding groups to modify the surface of the indium tin oxide (ITO) anode. The modified ITO surfaces are used in multilayer PLEDs, in which a green-emitting polymer, poly[2,7-(9,9-dihexylfluorene)-co-4,7-(2,1,3- benzothiadiazole)] (PFBT5), is sandwiched between a thermally crosslinked hole-transporting layer (HTL) and an electron-transporting layer (ETL). All tetra-phenyl-diamine (TPD)-based SAMs show significantly improved hole-injection between ITO and the HTL compared to oxygen plasma-treated ITO and simple aromatic SAMs on ITO. The device performance is consistent with the hole-transporting properties of triarylamine groups (measured by electrochemical measurements) and improved surface energy matching with the HTL. The turn-on voltage of the devices using SAM-modified anodes can be lowered by up to 3 V compared to bare ITO, yielding up to 18-fold increases in current density and up to 17-fold increases in brightness at 10 V. Variations in hole-injection and turn-on voltage between the different TPD-based molecules are attributed to the position of alkyl-spacers within the molecules. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.

Citation Format(s)

Self-assembled electroactive phosphonic acids on ITO : Maximizing hole-injection in polymer light-emitting diodes. / Bardecker, Julie A.; Ma, Hong; Kim, Taedong; Huang, Fei; Liu, Michelle S.; Cheng, Yen-Ju; Ting, Guy; Jen, Alex K.-Y.

In: Advanced Functional Materials, Vol. 18, No. 24, 22.12.2008, p. 3964-3971.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal