Painted LEDs make screen
Technology Research News
A research team from Germany has developed
a process for producing plastic, full-color flat screen displays that
is simpler and potentially cheaper than today's manufacturing methods
for organic light-emitting diode screens.
The researchers made the displays by spreading light-emitting
plastic, or polymer, molecules on a surface and exposing the polymers
to spots of ultraviolet light.
The method could produce color screens that are comparable in
quality to current flat screens, but are more rugged and require less
power, according Klaus Meerholz, who conducted the research at Munich
University in Germany and is now a professor of physical chemistry at
the University of Cologne. The method allows for "flat panels with high
brightness, extremely large viewing angle, and fast switching times,"
The method is "really fantastic," said Yang Yang, a professor
of materials science and engineering at the University of California at
Los Angeles. "The idea... has been discussed for years," he said. "However,
the device performance is always much poorer than... traditional devices."
The researchers did an excellent job of pushing the device performance
to a practical level, he said.
The researchers' prototypes produced pixels of comparable size,
sharpness and thus resolution as today's state-of-the-art flat screens.
The method has the potential to produce even smaller pixels, which would
make for screens of higher resolution than today's models, according to
The process is also "much simpler" than existing flat-screen manufacturing
methods, said Meerholz. This could translate into cheaper and more rugged
full-color screens for devices like cell phones and laptops.
The process could also be used to pattern polymers to make electronic
devices like transistors, sensors, and even wires, said Yang.
Key to the method is a polymer molecule that emits light and also
has photoresist properties. Photoresists are soluble in water, but shining
ultraviolet light on them causes the polymer molecules to each other,
rendering them insoluble.
This property allowed the researchers to pattern the polymer into
the separate, tiny dots, or pixels needed to produce a screen. The researchers
spread the polymer on a surface, shined ultraviolet light through a shadow
mask that contained 125-micron holes, then washed off the polymer that
was not cured. A micron is one thousandth of a millimeter.
By repeating the process with red-, blue- and green-emitting polymers,
the researchers were able to produce a full-color screen.
The method produced sharply defined dots, and in theory could
produce dots only a few microns wide, which would allow for even higher
resolutions, according to Meerholz.
The process is quite promising for full-color flat-panel displays,
mechanically flexible displays and, potentially for color image sensors,
said David Braun, a professor of electrical engineering at California
Polytechnic State University. The simultaneous control over pixel color
and pixel patterning, and the ability to produce nonsoluble electroluminescent
films, are novel, he said.
The researchers are currently testing the long-term stability
of screens produced using the method, according to Meerholz. They are
also working on producing true RGB colors, which are the standard colors
displayed by computer screens.
The method could produce practical displays within two years,
said Meerholz. "The technology is almost ready to go."
Meerholz's research colleagues were C. David Müller, Nina Reckefuss,
Paula Rudati and Holger Frohne from Munich University, Aurélie Falcou
and Heinrich Becker from Covion Organic Semiconductors in Germany and
Marcus Rojahn, Valérie Wiederhirn and Oskar Nuyken from the Technical
University of Munich. The work appeared in the February 20, 2003 issue
of Nature. The research was funded by Covion Organic Semiconductors, the
German Research Foundation (DFG) and the Bavarian Government.
Timeline: < 2 years
Funding: Corporate, Government
TRN Categories: Materials Science and Engineering; Optical
Computing, Optoelectronics and Photonics
Story Type: News
Related Elements: Technical paper, "Multi-Color Organic
Light-Emitting Displays by Solution Processing," Nature February 20, 2003.
March 28, 2003
Painted LEDs make screen
Fiber loop makes quantum
Glowing beads make
tiny bar codes
Alcohol powers fuel
Liquid crystals go 3D
liquids with heat
Research News Roundup
Research Watch blog
View from the High Ground Q&A
How It Works
News | Blog
Buy an ad link