A Blue ExcitonPolariton Organic LightEmitting Device

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A Blue Exciton-Polariton Organic Light-Emitting
Device
Scott Bradley, 6-1 (Electrical Engineering) Master
s of Engineering Thesis Proposal
Images in this presentation are from
Laboratory of Organic Optics and Electronics
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Introduction

• Project Motivation
• Background
• Organic Light-Emitting Devices (OLEDs)
• J-Aggregates of Cyanine Dyes
• Resonant-Cavity OLED
• Device Fabrication
• Research and Resources
• Experimental Methods
• Timeline and Goals
• Summary

Laboratory of Organic Optics and Electronics
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What is a Polariton?

• Quasi-particle consisting of a photon and an
  exciton.
• An exciton is an excited electron paired with a
  holeexcited state of a molecule.
• Exciton and photon pass energy back and forth.

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Project Motivation

• Exciton-polariton OLEDs have potential in optics
  applications.
• Existing work has established theory and created
  a red exciton-polariton OLED (J. Tischler).
• Work on a blue exciton-polariton OLED would allow
  for more research in fabrication.

Laboratory of Organic Optics and Electronics
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Background Organic Light-Emitting Devices
Example ETL
Example HTL
Laboratory of Organic Optics and Electronics
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Background J-Aggregates of Cyanine Dyes
We use polar organic dye molecules
-

which line up when deposited carefully
Called a J-Aggregate, named after Edwin Jelley of
Kodak, who described the phenomenon in Nature in
1936.
and strongly absorb only one type of light.
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Background Resonant-Cavity OLED

• Create a cavity tuned to the J-Aggregate
  absorption wavelength using silver mirrors.

• Thin layers of silver are semi-transparent, so
  light is able get in and out of the cavity.

Microcavity
As long as the wavelength of light
Laboratory of Organic Optics and Electronics
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Device Fabrication Dip-Coating
J-Aggregate-Polyelectrolyte Bi-Layers
Wavelength (nm)
Fabrication Demonstrated Using Bi-Layer
Deposition - Other J-Aggregates Likely Need
Langmuir-Blodgett
Absorption (Normalized)
Programmable Slide Stainer(1)
Wavenumber (cm-1)

• Picture of Stainer from www.leica-microsystems.com
  
• 400nm Bucher, Kuhn, Chem Phys Lett 6 (1970) 183
• 465nm Fukumoto,et al. Thin Solid Films 327329
  (1998) 748
• 550nm Era, Adachi, Chem Phys Lett 178 (1991) 488
• 623nm Rousseau, et al., Langmuir 16 (2000) 8865
• 890nm Rotermund, et al. Chem Phys 220 (1997) 385

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Research and Resources

• Plan to use dye with absorption around 465 nm.
• Process variation to improve fabrication
• pH variation of dye and polyelectrolyte
  solutions.
• Dye concentration.
• Number of layers.
• Substrate variation (currently glass/ITO slides).
• Different polyelectrolyte (currently PDAC).
• Might change mirror from metal to dielectric
  Bragg reflector (DBR).
• Planning to work with Prof. Vladimir Bulovic.
• LOOE has necessary fabrication equipment.

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Experimental Methods

• Electroluminescence measurements on patterned
  devices. LOOE
• Photoluminescence measurements using 408 nm and
  higher energy lasers for excitation (fix
  excitation and scan through detection
  wavelengths). LOOE
• Photoluminescence-excitation measurements (fix
  detection and scan through excitation). other
  CMSE groups
• Reflection and transmission measurements using
  UV-Vis-NIR spectrometer. CMSE Shared Analytical
  Lab

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Goals and Timeline

• Goals
• Build a blue exciton-polariton OLED.
• Research fabrication process parameters.
• Timeline
• Currently doing related work in UROP position.
• Be trained on necessary equipment by end of
  senior year.
• Revisit M. Eng. thesis proposal and goals in
  spring 2004.
• 6.728 in Fall 2004, 6.730 in Spring 2005.
• Research process parameters to refine J-Aggregate
  bi-layer deposition with 465 nm dye (fall 2004).
• Fabricate blue exciton-polariton OLED (spring
  2005).

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Summary

• Blue exciton-polariton OLED fabrication and
  research could provide more information for
  further use of J-Aggregate-based devices.
• Further understanding of deposition process could
  help in creation of J-Aggregated-based devices in
  NIR and IR.