Quantum dots are another new downconversion material. Measuring a few nanometers across, quantum dots have a size-dependent emission with a half width of only nanometers. Along with efficiencies that run 97 percent, such attributes make them useful in LEDs.
Nanosys Inc. of Milpitas, Calif., makes quantum dots, putting them into polymer films that can be dropped into the standard LED manufacturing flow. The polymer acts as both a structural material and a protective barrier so that the quantum dots are not damaged by oxygen or moisture.
The company’s red- and green-emitting quantum dots improve LED efficiency, thanks to a full width half maximum under 30 nm. “That enables us to match the spectrum of the backlight to the color filters. That means we’re not spending any energy generating light that doesn’t go through,” said Jeff Yurek, product marketing manager.