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Edited by Tobin J. Marks, Northwestern University, Evanston, IL, and approved October 17, 2003 (received for review July 5, 2003)
Abstract
Although tremendous progress has been made in organic light-emitting diodes (OLEDs), with few exceptions they are fabricated in the standard way by sequentially depositing active layers and electrodes onto a substrate. Here we describe a different approach for building OLEDs, which is based on physical lamination of thin metal electrodes supported by an elastomeric layer against an electroluminescent organic. This method relies only on van der Waals interactions to establish spatially homogeneous, intimate contacts between the electrodes and the organic. We find that devices fabricated in this manner have better performance than those constructed with standard processing techniques. The lamination approach avoids forms of disruption that can be introduced at the electrode/organic interface by metal evaporation and has a reduced sensitivity to pinhole or partial pinhole defects. In addition, because this form of “soft” contact lamination is intrinsically compatible with the techniques of soft lithography, it is easy to build patterned OLEDs with feature sizes into the nanometer regime. This method provides a new route to OLEDs for applications ranging from high performance displays to storage and lithography systems that rely on subwavelength light sources.
Footnotes
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↵ † To whom correspondence should be addressed. E-mail: taew.lee{at}samsung.com or jrogers{at}uiuc.edu.
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This paper was submitted directly (Track II) to the PNAS office.
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Abbreviations: EL, electroluminescence; ITO, indium tin oxide; MEH-PPV, poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylenevinylene]; OLED, organic light-emitting diode; PDMS, poly(dimethylsiloxane); ph/el, photons per electron; PL, photoluminescence; ScL, soft contact lamination; TBABF4, tetra-n-butylammonium tetrafluoroborate.
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↵ § For comparison, a thermally evaporated device of the same structure with Au electrode showed 5.9 × 10–5% quantum efficiency for ITO-positive direction and 1.6 × 10–4% quantum efficiency for Au-positive direction.
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↵ ¶ The degree of quenching rates and blue shift in spectra because of bond disruption depends on the evporation method (electron beam or thermal), the evaporation rate, and the molecular weight and chemical structures of the material, etc.
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↵ ∥ We put high-concentration (5 mM) octadecanethiol solution on the patterned stamp to generate high-contrast patterned images.
- Copyright © 2004, The National Academy of Sciences
Organic light-emitting diodes formed by soft contact lamination
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