Laser-induced forward transfer of polymer light-emitting diode pixels with increased charge injection

James Shaw-Stewart, Thomas Lippert, Matthias Nagel, Frank Nüesch, Alexander Wokaun

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Laser-induced forward transfer (LIFT) has been used to print 0.6 mm × 0.5 mm polymer lightemitting diode (PLED) pixels with poly[2-methoxy, 5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) as the light-emitting polymer. The donor substrate used in the LIFT process is covered by a sacrificial triazene polymer (TP) release layer on top of which the aluminium cathode and functional MEH-PPV layers are deposited. To enhance electron injection into the MEH-PPV layer, a thin poly-(ethylene oxide) (PEO) layer on the Al cathode or a blend of MEH-PPV and PEO was used. These donor substrates have been transferred onto both plain indium tin oxide (ITO) and bilayer ITO/PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly-(styrenesulfonate) blend) receiver substrates to create the PLED pixels. For comparison, devices were fabricated in a conventional manner on ITO substrates coated with a PEDOT:PSS hole-transporting layer. Compared to multilayer devices without PEO, devices with ITO/PEDOT:PSS/MEH-PPV:PEO blend/Al architecture show a 100 fold increase of luminous efficiency (LE) reaching a maximum of 0.45 cd/A for the blend at a brightness of 400 cd/m 2. A similar increase is obtained for the polymer lightemitting diode (PLED) pixels deposited by the LIFT process, although the maximum luminous efficiency only reaches 0.05 cd/A for MEH-PPV:PEO blend, which we have attributed to the fact that LIFT transfer was carried out in an ambient atmosphere. For all devices, we confirm a strong increase in device performance and stability when using a PEDOT:PSS film on the ITO anode. For PLEDs produced by LIFT, we show that a 25 nm thick PEDOT:PSS layer on the ITO receiver substrate considerably reduces the laser fluence required for pixel transfer from 250 mJ/cm 2 without the layer to only 80 mJ/cm 2 with the layer.

Original languageEnglish
Pages (from-to)309-316
Number of pages8
JournalACS Applied Materials and Interfaces
Volume3
Issue number2
DOIs
Publication statusPublished - 23 Feb 2011
Externally publishedYes

Keywords

  • Laser deposition
  • LIFT
  • PLED pixels
  • Triazene polymer

ASJC Scopus subject areas

  • Materials Science(all)

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