• Vladimir Bulovic, assistant professor in electrical engineering and computer science, chemistry graduate student Jonathan Steckel and chemistry professor Moungi Bawendi (from left), watch as Seth Coe, a graduate student in electrical engineering and computer science, inspects a vial of fluorescing quantum dots in preparation for fabricating a light-emitting device.

    Photo / Donna Coveney

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Quantum-dot LED may be the future of screens

MIT researchers have combined organic materials with high-performing inorganic nanocrystals to create a hybrid optoelectronic structure--a quantum dot-organic light-emitting device (QD-OLED) that may one day replace liquid crystal displays (LCDs) as the flat-panel display of choice for consumer electronics.

The work, reported in the Dec. 19 issue of Nature, is a collaborative effort between Moungi G. Bawendi, professor of chemistry, and Vladimir Bulovic, assistant professor of electrical engineering and computer science. Bulovic is also affiliated with the Research Laboratory of Electronics.

Bawendi studies the electronic and optical properties of semiconductor nanocrystal quantum dots for applications ranging from biology to optical devices. Also called artificial atoms, quantum dots are nanometer-scale "boxes" that selectively hold or release electrons.

Unlike traditional LCDs, which must be lit from behind, quantum dots generate their own light. Depending on their size, the dots can be "tuned" to emit any color in the rainbow. And the colors of light they produce are much more saturated than that of other sources.

Bulovic is pursuing the use of organic and nanostructured materials as active electronic elements. Bawendi and Bulovic, with electrical engineering and computer science graduate student Seth A. Coe and chemistry graduate student Wing-Keung Woo, teamed up through MIT's Center for Materials Science and Engineering to create a new, improved QD-OLED.

This latest MIT QD-OLED contains only a single layer of quantum dots sandwiched between two organic thin films. (Previous QD-OLEDs used 10-20 layers.) The researchers have demonstrated organized assemblies over a 1-square centimeter area and the same principle could be used to make bigger components.

The MIT team's method of combining organic and inorganic materials may pave the way for new technologies and enhance understanding of the physics of these materials.

In addition to being used for extraordinarily thin, bright flat-panel displays, the QD-OLEDs also may be used in a variety of other applications; to calibrate wavelengths for scientific purposes, generate wavelengths visible only to robot eyes or "miniaturize scientific equipment in ways we haven't yet imagined," Bawendi said.

The QD-OLEDs created in the MIT study have a 25-fold improvement in luminescent power efficiency over previous QD-OLEDs. The MIT researchers note that in time, the devices may be made even more efficient and achieve even higher color saturation.

"One of the goals is to demonstrate a display that is stable, simple to produce, flat, high-resolution and that uses minimal power," Bulovic said.

A version of this article appeared in MIT Tech Talk on January 8, 2003.

Topics: Electrical engineering and electronics


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