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Posted on May 12, 2009 by  & 

Photoluminescent nanocrystals with the potential for new lighting

Exploring new types of low-cost lighting, scientists at the University of Rochester together with researchers at the Eastman Kodak Company created new "non-blinking" nanocrystals that constantly emit light. This development has the potential to be an incredibly cheap alternative for lighting applications or even an OLED successor.
Nanocrystals, just a billionth of a meter in size, can absorb or radiate photons, by which they usually undergo what is called "blinking". This change between the light emitting state and a "dark" period occurs because the energy of an absorbed photon is randomly transformed into heat instead of radiating away.
"A nanocrystal that has just absorbed the energy from a photon has two choices to rid itself of the excess energy—emission of light or of heat," says Todd Krauss, associate professor of chemistry at the University of Rochester and lead author on the study.
Nanocrystals normally have a semiconductive core with a sharp boundary that divides it from the also semiconductive protective shell. The core/shell CdZnSe/ZnSe semiconductor nanocrystals created at the University of Rochester differ from that. They have a continuous gradient from the core to the shell, which eliminates the "blinking" and results in a steady stream of emitted photons.
This could revolutionize lasers and lighting. With blink-free nanocrystals, lighting applications could be fabricated in an easier and cheaper process, which e.g. would apply only one fabrication step to create low-threshold lasers. To alter the color of the laser only the size of the nanocrystal needs to be changed.
Krauss even believes that this could become OLED's successor. The idea is simply "paint" a grid of nanocrystals - emitting different colors - onto a flat surface, and with that, create paper-thin displays or even light emitting walls.
Apart from the Eastman Kodak Company, this study was also funded by the U.S. Department of Energy, the National Science Foundation, the University of Rochester Center for Electronic Imaging Systems, the Cornell Center for Nanoscale Systems, the Office of Naval Research, and the Alexander von Humboldt Foundation.
About the University of Rochester
The University of Rochester ( External Link) is one of the nation's leading private universities. Located in Rochester, N.Y., the University gives students exceptional opportunities for interdisciplinary study and close collaboration with faculty through its unique cluster-based curriculum. Its College of Arts, Sciences, and Engineering is complemented by the Eastman School of Music, Simon School of Business, Warner School of Education, Laboratory for Laser Energetics, Schools of Medicine and Nursing, and the Memorial Art Gallery.
About Eastman Kodak
Kodak is the world's foremost imaging innovator, providing leading products and services to the photographic, graphic communications and healthcare markets. With sales of $14.3 billion in 2005, the company is committed to a digitally oriented growth strategy focused on helping people better use meaningful images and information in their life and work. Consumers use Kodak's system of digital and traditional image capture products and services to take, print and share their pictures anytime, anywhere.
Businesses effectively communicate with customers worldwide using Kodak solutions for prepress, conventional and digital printing and document imaging. Creative Professionals rely on Kodak technology to uniquely tell their story through moving or still images. Leading Healthcare organizations rely on Kodak's innovative products, services and customised workflow solutions to help improve patient care and maximize efficiency and information sharing, within and across their enterprise.
Source of top image: Krauss' new "non-blinking" nanocrystals (courtesy of University of Rochester).

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Posted on: May 12, 2009

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