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

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

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.

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

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

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.

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

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 www.leica-microsystems.com 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

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.

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]

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).

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.