NEW LAMPS FOR OLD.
OPPORTUNITIES FOR CHEMISTS IN LIGHTING AND DISPLAY TECHNOLOGIES

Co-Sponsored by the
Committee on Science,
Division of Chemical Education,
Division of Inorganic Chemistry,
Division of Organic Chemistry,
Division of Polymeric Materials: Science & Engineering
and the
Materials Research Science and Engineering Center
for Nanostructured Materials and Interfaces
University of Wisconsin - Madison

J. Katz, Program Secretary
A. B. Ellis, Program Chair

SUNDAY AFTERNOON April 1, 2001
Unknown Site
Unknown Room

A. B. Ellis, Organizer

Program

1:25 — Opening Remarks by A. B. Ellis

1:30 — 1. Challenges in solid-state lighting: a new industry based on compound semiconductor light-emitting diodes. S. A. Stockman

2:10 — 2. Group III-nitride materials for high brightness light-emitting diodes. J. M. Redwing

2:50 — Intermission.

2:55 — 3. Enhancing the efficiencies, color purities and lifetimes of organic light emitting diodes M. E. Thompson, S. R. Forrest

3:35 — 4. Opportunities for chemists in organic LEDs and other display technologies. D. J. Gisser

4:15 — Intermission.

4:20 — 5. Lighting up your chemistry class. G. C. Lisensky, K. J. Nordell, S. M. Condren, J. G. Breitzer, C. G. Widstrand, A. B. Ellis

Abstracts

Challenges in solid-state lighting: a new industry based on compound semiconductor light-emitting diodes

Stephen A. Stockman, III-V Materials R&D, LumiLeds Lighting, 370 West Trimble Road, MS 91-ML, San Jose, CA 95131, Fax: 408-435-6335, steve.stockman@lumileds.com

During the 1990s, great progress was made in the development of inorganic materials for visible light-emitting diodes (LEDs). As a result of these breakthroughs in InGaN and AlGaInP materials technology, the luminous efficiency of visible LEDs now rivals or exceeds that of conventional lighting technologies. The primary advantages of LEDs over competing technologies are reliability and energy efficiency. Over the past few years, LEDs have begun to penetrate commercial markets such as automotive lighting, traffic signals, and outdoor full-color signs. We will review these markets and the current state-of-the-art in LED technology, and highlight current challenges in LED design, fabrication, and high-volume manufacturing. Power limitations and the high cost of LED-based lighting systems have so far prevented widespread adoption in the $40B lighting market. In future LED lighting products, higher power and lower cost will be achieved by using a small number of high-power LEDs. These LEDs must operate at power levels approximately 10 to 100 times higher than those available today, while maintaining excellent reliability and high efficiency. This introduces a new set of considerations into the design and manufacture of LEDs, and we will present a preview of these future challenges.

Acrobat .pdf file of Stockman's presentation.

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Group III-nitride materials for high brightness light-emitting diodes

Joan M. Redwing, Department of Material Science and Engineering, The Pennsylvania State University, 108 Steidle Bldg, University Park, PA 16802, Fax: 814-865-2917, jmr31@psu.edu

The group III-nitrides, (Al,Ga,In)N, have emerged as the premier material system for the fabrication of short wavelength light emitting devices operating in the UV to green. Metalorganic vapor phase epitaxy (MOVPE) is the most common technique used to fabricate GaN-based thin films. The epitaxial growth of (Al,Ga,In)N materials by MOVPE is complicated by several factors including the lack of a lattice matched substrate, gas phase pre-reactions, hydrogen passivation of acceptors and the low thermal stability of indium-containing alloys. In spite of these difficulties, commercial high brightness LEDs, short wavelength laser diodes and high power microwave transistors have all been produced using this technique. This presentation will discuss some of the unique complexities of GaN growth by MOVPE, highlighting areas in which growth chemistry, kinetic and thermodynamic constraints, and thin film stress and defect formation, play an important role.[Back to Program]

Enhancing the Efficiencies, Color Purities and Lifetimes of Organic Light Emitting Diodes

Mark E. Thompson, Chemistry Department, University of Southern California, Los Angeles, CA 90089-0744, Fax: 213-740-8594, met@usc.edu, and Stephen R. Forrest, Department of Electrical Engineering, Princeton University

My presentation will begin with a general discussion of electroluminescence and the construction of organic light emitting diodes. In order to use organic light emitting diodes (OLEDs) in display and lighting applications it is important to be able to accurately tune the color of emission. Doping of OLEDs with fluorescent dyes has been known for many years as a useful means to control the color of OLEDs. Unfortunately, the use of a fluorescent dye leads to an upper limit of 25% on the internal quantum efficiency, due to the small fraction of singlet excitons created on hole-electron recombination. The use of phosphorescent dopants, however, allows the efficient utilization of both singlet and triplet excitons, removing the 25% upper limit on the internal efficiency. We have fabricated saturated red, orange, yellow and green OLEDs, utilizing phosphorescent dopants. The quantum efficiencies of these devices are quite good, with measured external efficiencies as high as 15% (internal eff. » 75%). The phosphorescent dopants in these devices are heavy metal containing molecules (i.e. Pt, and Ir), prepared as both metalloporphyrins and organometallic complexes. The heavy metals in these metal complexes gives efficient emission from triplet or highly spin orbit coupled states. I will discuss the important parameters in designing electrophosphorescent OLEDs as well as their strengths and limitations. Accelerated aging studies, on packaged devices, have shown that phosphorescence based OLEDs can have very long device lifetimes. These studies will also be discussed.

Acrobat .pdf file of Thompson's presentation.

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Opportunities for chemists in organic LEDs and other display technologies

Daniel J. Gisser, Eastman Kodak Company, 1999 Lake Avenue, Rochester, NY 14650-2138, Fax: 716-722-5548, daniel.gisser@kodak.com

Organic Light Emitting Diodes were invented by chemists at Eastman Kodak Company in the mid 1980s, and now are widely viewed as the next generation of flat panel display technology and as a candidate for general purpose lighting. Significant materials, device, and manufacturing improvements are needed for this technology to reach mainstream applications. Chemists, working alongside electrical engineers, physicists, and other specialists, will play a special role in this development. More broadly, chemists are afforded significant opportunities to contribute to other display and lighting technologies. This talk will highlight some known opportunities for chemists in these fields.

Acrobat .pdf file of Gisser's presentation.

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Lighting up your chemistry class

George C. Lisensky¹, Karen J. Nordell², S. Michael Condren³, Jonathan G. Breitzer⁴, Cindy G. Widstrand⁴, and Arthur B. Ellis⁴. (1) Department of Chemistry, Beloit College, 700 College Street, Beloit, WI 53511, Fax: 608-363-2718, lisensky@beloit.edu, (2) Department of Chemistry, Lawrence University, (3) Department of Chemistry, Christian Brothers University, (4) Department of Chemistry, University of Wisconsin-Madison

New lighting and display technologies provide opportunities to illustrate fundamental chemical principles connecting composition, structure, periodic properties, and spectroscopy. Demonstrations illustrating these relationships will be presented. Some of the resources available for teaching, produced with National Science Foundation support, include: Build a Better CD Player: How Can You Get Blue Light From a Solid? (Chem Connections Module available from John Wiley & Sons), Exploring the Nanoworld (activity kit available from the Institute for Chemical Education), and http://mrsec.wisc.edu/edetc (education and outreach efforts of the Materials Research Science and Engineering Center on Nanostructured Materials and Interfaces at the University of Wisconsin-Madison).

Acrobat .pdf file of Lisensky's presentation.

[Back to Program]