SBIR Phase I: Silicon Quantum-dot Phosphors for LED General Illumination

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This Small Business Innovation Research Phase I project seeks to greatly improve the light output of white-light light-emitting diodes (LEDs) using fluorescent nanoparticles or quantum dots (QDs) made from silicon. The most efficient and economical design for a contemporary white LED is based on a blue LED chip which excites a yellow-emitting rare-earth phosphor. This particular mix of blue and yellow hues produces a cool and bluish-white light which cannot faithfully render some colors in illuminated objects, especially in the case of red tones. The proposed solution places red-color-enhancing silicon-QDs (SiQDs) in the beam-path of these white LEDs; by absorbing some of the blue light output and re-emitting red light, the SiQDs complement the absent red spectrum, and thus improve the overall color rendering performance. The company has thus far established baseline methodologies for the scalable production of brightly luminescing SiQDs. This Phase I project will enable the company to improve the performance of said SiQDs, and also establish their long-term performance stability.The broader impact/commercial potential of this project is to develop SiQDs that can ultimately replace current rare-earth-derived phosphors. China has a virtual monopoly over global rare-earth supply, and is enacting draconian restrictions on extraction and exportation to capitalize on its position. The cost of rare-earth phosphors used in packaged white-light LEDs is thus set to soar because of the dwindling supply and increasing market demand for additional rare-earth phosphors (such as europium-doped nitrides or sulfides) to generate reds for premium LED offerings. Hence, an earth-abundant and cost-effective alternative phosphor material is desperately needed. Semiconductor QDs are considered a promising solution due to their wide-range wavelength-tunability and high photoluminescence quantum yield. Because of the inert nature and the abundance of silicon, SiQDs can provide a non-toxic, high-stability, and lower cost solution, in comparison with established heavy-metal cadmium-chalcogenide QD materials (such as CdSe QDs). The project will serve as the first step in the development of a repertoire of products which permit the creation of all visible light wavelengths via SiQD-phosphors, allowing white-light LEDs to be free from the need for rare-earth- and cadmium-based phosphors. This will in turn make LED lighting more aesthetically attractive, affordable, and environmentally friendly.