1. 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

2. 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

3. What is a Polariton?
Quasi-particle consisting of a photon and an exciton.
An exciton is an excited electron paired with a hole—excited state of a molecule.
Exciton and photon pass energy back and forth.

4. 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

5. ETL HTL Background: Organic Light-Emitting Devices E LUMO HOMO+
electrons and holes
form excitons
(bound e--h+ pairs)
some excitons radiate
HOMO
LUMO
recombination region
ETL
HTL E _
Example ETL
Example HTL
Laboratory of Organic Optics and Electronics

6. 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.

7. 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

8. Dip-Coating J-Aggregate-Polyelectrolyte Bi-Layers
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
400nm: Bucher, Kuhn, Chem Phys Lett 6 (1970) 183
465nm: Fukumoto,et al. Thin Solid Films 327–329 (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

9. 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 Bulović.
LOOE has necessary fabrication equipment.

10. 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]

11. 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, 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).

12. 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.