Shedding light on quantum dots

Hybridising an inorganic nanocrystal and a quantum dot lead to a quantum dot-organic light-emitting device (QD-OLED) a new kind of optoelectronic device that could lead to new types of flat panel displays to supersede liquid crystal displays in everything from mobile devices to TV sets.

Moungi Bawendi

Vladimir Bulovic

Moungi Bawendi and Vladimir Bulovic of the Massachusetts Institute of Technology collaborated on the device to bring together their two areas of expertise. 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. Bulovic, on the other hand, is pursuing the use of organic and nanostructured materials as active electronic elements.

Team member Seth Coe inspects a vial of fluorescing quantum dots in preparation for fabricating a QD-OLED. (Photo by Donna Coveney)

Unlike traditional LCDs, which must be lit from behind to work, quantum dots generate their own light. Depending on their size, the dots can be "tuned" to emit any color with a 25-fold improvement in luminescent power efficiency over previous QD-OLEDs. The colors are very rich but the team suggests they could be saturated even more if desired. "We have not reached the fundamental limits of device performance in terms of both quantum efficiency and color saturation," they explain in the journal Nature.

Quantum dots

The MIT QD-OLED contains only a single layer of quantum dots sandwiched between two organic thin films and the researchers have demonstrated organized assemblies over an area of a square centimeter but hint that the same principle could be used for bigger components. "One of the goals is to demonstrate a display that is stable, simple to produce, flat, high-resolution, and that uses minimal power," Bulovic explains.