Highly Bright, Heavy Metal-Free, and Stable Doped Semiconductor Nanophosphors for Economical Solid State Lighting Alternatives

There is growing concern about how to limit the release of mercury into the environment. One significant source of mercury is found in fluorescent lamps. Recently, however, compact fluorescent lamps have been heavily promoted in order to conserve electrical energy. While it is true that switching to energy efficient lighting is one of the easiest ways to save energy, reduce CO2 emissions, and save money in the short-term, fluorescent lighting is not the ideal long-term solution precisely because fluorescent lamps contain toxic mercury vapor. Solid state lighting (SSL), on the other hand, holds even greater promise. White LEDs are already more efficient than fluorescent lamps, do not contain heavy metal toxins, and are available with decent color rendering abilities. What holds SSL back is the high price per lumen ration. Only if the cost can be reduced with SSL be able to make significant progress in replacing incandescent and fluorescent lighting. One way to do this is to improve the luminous efficiency of the white LEDs so that more light is emitted at the same price. NN-Labs proposes to complete line of transition-metal doped semiconductor nanocrystals (D-dots ¿) to be used as nanophosphors for white LEDs. Current white LEDs rely on micron-sized phosphors that suffer up to 50% losses in efficiency due to backscattering of fluorescence. Nano-sized phosphors, because they are much smaller than the wavelengths of visible light, do not scatter light. By using D-dots ¿ nanophosphors, white LEDs could improve their luminous efficiencies up to 100% compared with bulk phosphors. Furthermore, D-dots ¿ are more ideally suited for use in LEDs than other kinds of nanophosphors, such as quantum dots, because D-dots ¿ are immune to re-absorption losses that plague intrinsic nanocrystal emitters. This SBIR Phase II project will develop a full spectrum of D-dots ¿ emitters with high photoluminescence quantum yields, optimal absorption profiles, and long photo and thermal stability lifetimes required of high brightness (HB) LED phosphors. Also, NN-Labs will work together with its industrial collaborator, Dow Corning, to develop manophosphor/encapsulant composites and fully integrate them into HB LED manufacturing processes. The market for HB LEDs was $4.2 billion in 2006 and is expected to grown to $9 billion in 2009. Estimations show the LED Phosphor market associated with HB white LEDs was $180 million in 2006 and should reach $2.3 billion by 2015. NN-Labs predicts revenue from sales of D-dots ¿ to reach $383 million by 2015.