Organic light emitting diode arrays are showing great promise as replacements for liquid crystal displays. The OLEDs offer the advantage of emitting light whereas the LCDs have to be back lit. This is an excellent example of nanotechnology.
Basic OLED design
Copyright Chemical & Engineering News, June 26, 2000
The OLED is composed of one or more specialty organic/polymer materials between two electrodes, one of which is transparent. Applying a voltage across the electrodes causes holes and electrons to be created. Light is emitted when these electrons and holes recombine. The color of light is dependent on the organic/polyer compounds involved. Full color OLED panels can be created by using a combination of red, green, and blue sections, as shown above.
OLEDs show promise for replacing some applications for LCDs. Since the molecules emit light, there is no need for backlighting the display, saving tremendously on power. The light emitted varies in color. The use of red, green, and blue emitting polymers eliminates the need for the filters needed in full color LCD displays.
The promise of the use of OLEDs in large color televisions has not lived up to the hype. The half-life of the blue OLEDs is still too short for this application. However, full displays for user products that are expected to be replaced in a few years with newer/better versions, such as cell phones, music players, digital camera displays, etc., are being produced. In the mean research continues on the blue OLEDs to get longer half-lifes, the length of time for the luminance emitted to decrease to half of its original value.
Kodak describes what they are and their attributes.
Universal Display Corporation describes the materials involved and related technologies: TOLED (transparent and top-emitting OLED), FOLED (flexible OLEDs), and PHOLED (phosphorescent OLED). They have web pages devoted to active and passive applications as well as Organic Vapor Phase Deposition. There is even a page devoted to White PHOLED Lighting.
They also describe their latest developments.
"Coming soon to a laptop near you" describes recent developments in OLEDs in laptop computer monitors.
Click here for more information about Inorganic LEDs.
"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, presentation at the LED Symposium at the San Diego ACS National Meeting April 1, 2001.
"Opportunities for chemists in organic LEDs and other display technologies" Daniel J. Gisser, Eastman Kodak Company, 1999 Lake Avenue, Rochester, NY 14650-2138, presentation at the LED Symposium at the San Diego ACS National Meeting April 1, 2001.
An Easily
Prepared Organic LED Using [Ru(bpy)3]2+ by Jonathan
Breitzer and Joel Hassenzahl
LED fabrication procedure modified from Frank G. Gao and Allen J. Bard, "Solid-State
Organic Light-Emitting Diodes Based on Tris(2,2'-bipyridine)ruthenium(II)
Complexes", Journal of the American Chemical Society, 122(30), 7426-7427
(2000)
[Ru(bpy)3](BF4)2 synthesis modified from
John A. Broomhead and Charles G. Young, Inorg. Syn. 28, 338-340 (1990).