With the age of the incandescent¹ light（白炽灯） bulb fading rapidly, the holy grail of the lighting² industry is to develop a highly efficient form of solid-state lighting that produces high quality white light. One of the few alternative technologies that produce pure white light is white-light quantum dots. These are ultra-small fluorescent³（荧光的） beads⁴ of cadmium selenide that can convert the blue light produced by an LED into a warm white light with a spectrum⁵ similar to that of incandescent light. (By contrast, compact fluorescent tubes and most white-light LEDs emit a combination of monochromatic⁶ colors that simulate white light).

Seven years ago, when white-light quantum dots were discovered accidentally in a Vanderbilt chemistry lab, their efficiency was too low for commercial applications and several experts predicted that it would be impossible to raise it to practical levels. Today, however, Vanderbilt researchers have proven those predictions wrong by reporting that they have successfully boosted the fluorescent efficiency of these nanocrystals from an original level of three percent to as high as 45 percent.

Potential commercial applications

"Forty-five percent is as high as the efficiency of some commercial phosphors（荧光粉） which suggests that white-light quantum dots can now be used in some special lighting applications," said Sandra Rosenthal, the Jack⁷ and Pamela Egan Chair of Chemistry, who directed the research which is described online in the Journal of the American Chemical Society. "The fact that we have successfully boosted their efficiency by more than 10 times also means that it should be possible to improve their efficiency even further."

The general measure for the overall efficiency of lighting devices is called luminous⁸ efficiency and it measures the amount of visible light (lumens) a device produces per watt⁹. An incandescent light bulb produces about 15 lumens/watt, while a fluorescent tubes put out about 100 lumens/watt. White light LEDs currently on the market range from 28 to 93 lumens/watt.

"We calculate that if you combine our enhanced quantum dots with the most efficient ultraviolet LED, the hybrid¹⁰ device would have a luminous efficiency of about 40 lumens/watt," reported James McBride, research assistant professor of chemistry who has been involved in the research from its inception¹¹. "There is lots of room to improve the efficiency of UV LEDS and the improvements would translate directly into a higher efficiencies in the hybrid."