Laboratory of Organic Optics and Electronics

A Blue Exciton-Polariton Organic Light-Emitting

Device

Laboratory of Organic Optics and Electronics

Scott Bradley, 6-1 (Electrical Engineering)

Master’s of Engineering Thesis Proposal

Images in this presentation are from:

Laboratory of Organic Optics and Electronics

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

Laboratory of Organic Optics and Electronics

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.

Laboratory of Organic Optics and Electronics

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

Laboratory of Organic Optics and Electronics

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electrons and holesform excitonsexcitons

(bound e--h+ pairs)

some excitons radiatesome excitons radiate

HOMO

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ETLHTL

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Background: Organic Light-Emitting Devices

Example HTL Example ETL

Laboratory of Organic Optics and Electronics

Laboratory of Organic Optics and Electronics

Background: J-Aggregates of Cyanine Dyes

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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.

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…and strongly absorb only one type of light.

Laboratory of Organic Optics and ElectronicsLaboratory of Organic Optics and Electronics

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.

As long as the wavelength of light

Microcavity

Laboratory of Organic Optics and Electronics

Device Fabrication: Dip-Coating J-Aggregate-Polyelectrolyte Bi-Layers

Programmable Slide Stainer(1)

(1) Picture of Stainer from www.leica-microsystems.com(2) 400nm: Bucher, Kuhn, Chem Phys Lett 6 (1970) 183(3) 465nm: Fukumoto,et al. Thin Solid Films 327–329 (1998) 748(4) 550nm: Era, Adachi, Chem Phys Lett 178 (1991) 488(5) 623nm: Rousseau, et al., Langmuir 16 (2000) 8865(6) 890nm: Rotermund, et al. Chem Phys 220 (1997) 385

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Fabrication Demonstrated Using Bi-Layer Deposition - Other J-Aggregates Likely Need Langmuir-Blodgett

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Pk 400 nm, FWHM 10 nm Pk 465 nm, FWHM 12 nm Pk 550 nm, FWHM 20 nm Pk 594 nm, FWHM 17 nm Pk 623 nm, FWHM 21 nm Pk 695 nm, FWHM 20 nm Pk 890 nm, FWHM 50 nm

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Laboratory of Organic Optics and Electronics

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.

Laboratory of Organic Optics and Electronics

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]

Laboratory of Organic Optics and Electronics

Goals and Timeline

Goals:1. Build a blue exciton-polariton OLED.2. 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).

Laboratory of Organic Optics and Electronics

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.