The QD Vision optics absorb the energy from the phosphor-coated LEDs and reemit it at a new mix of wavelengths. Coe-Sullivan says that the color rendering index–a measure of what colors look like under the light–of the company’s optic is 90, compared with the 70s for the LEDs without the optic. Sunlight has a color rendering index of 100, and standard incandescent lightbulbs about 99. The QD Vision light is far more efficient than an incandescent, producing 65 lumens per watt of electricity, whereas an incandescent produces about 15 lumens per watt. A compact fluorescent lightbulb produces about 30 lumens per watt; has a cooler, harsher light than the QD Vision lamp; and has the added environmental problem of containing mercury.
“These are good numbers,” says Nadarajah Narendran, director of the Lighting Research Center at Rensselaer Polytechnic Institute. “This may be the first market-ready product [based on quantum dots], so in that sense they might be unique,” he says. “You have to have all the ingredients right.” Those include not only lifetime, energy efficiency, and color: “Price is the most important one at the moment.”
Companies are struggling to get the cost of their LED-based bulb replacements down to $65 and below. The Nexxus lamp could cost about $100. Button says that if you consider how much a user will save in electricity, the cost of replacement bulbs, and the labor that would otherwise be needed to replace multiple ceiling fixtures over the projected seven-and-a-half-year lifetime, the lamp will be competitive.
The two companies displayed their lamp last week at the Lightfair International trade show in New York, and they say that they’ll have it available for sale by the end of the year. Meanwhile, Button says that there’s nothing exclusive about QD Vision’s deal with Nexxus, and that he hopes to work with other companies to produce more products for general lighting. QD Vision had initially focused on using quantum dots to make better display screens for computers and other devices. It’s still in that business, but given that most of the display makers are in Asia, the company felt as though lighting would give the company a quicker entry into the market, Coe-Sullivan says.
The beauty of QD Vision’s technology, Button says, is that it’s just a small addition to existing LEDs designed for standard light fixtures. “They’re getting a market without changing anything,” he says. “You give us a light input, and we’re going to improve the color without diminishing the efficiency.”