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

At present, the most economically efficient lighting technologies rely on discharge emission from mercury vapors. Mercury, however, is extremely toxic and has the potential to accumulate in the human body over time. The alarming increase in mercury levels in our soils, sediments, and waters is driving the push to find economically viable alternative lighting sources that do not contain mercury. The object of this project is to combine nontoxic doped semiconductor nanocrystal phosphors with existing high-efficiency blue/ultraviolet InGaN light-emitting diodes to produce bright, efficient, and affordable solid state lighting as a replacement for mercury-containing fluorescent lights. Doped semiconductor nanocrystal phosphors that do not contain heavy metals such as lead, mercury, or cadmium are ideal for such an application because, unlike bulk phosphors that suffer from scattering losses, the extremely small size of nanophosphors makes them immune to Mie-type scattering. Also, their synthesis and production methods are relatively cheap and easy, they can be processed from solution in a wide variety of solvents, and they can be blended with polymers and other encapsulants to form highly fluorescent composite materials conformable to nearly any surface. Their emission color can be tunable over a large visible range, and, unlike intrinsic semiconductor nanocrystal emitters, doped nanocrystals have no reabsorption or fluorescence resonance energy transfer losses and, therefore, can be deposited in high-packing densities for maximum luminous output and efficiency. Phase I of this project will concentrate on using our exclusive yellow-orange emitting Mn-doped ZnSe nanocrystal phosphor technology to examine the general feasibility and applicability of this new and exciting technology to the manufacture of solid state lighting that is at least competitive with conventional mercury-containing fluorescent light bulbs in terms of both cost and efficiency. Phase II will focus more on development and synthesis scale-up of a full spectral range of doped semiconductor nanocrystal phosphors with high photoluminescence quantum yields. Phase II also will put more focus onto the commercial aspects, including the development of working prototypes and investor relations. This project, if successful, will have a far-reaching environmental impact. The vision is to replace billions of mercury-containing fluorescent lights with nontoxic nanophosphor solid state lighting units, effectively eliminating a major source of mercury release into the environment.