PHOSPHORS FOR LED LIGHTING
The development of LED lighting technology provides an excellent opportunity for creating alternative light sources that more efficient, longer lasting, and readily accessible than traditional lighting. LEDs are all around us as traffic lights, high-definition televisions, and automobile headlights. However, the most critical need for this technology is for adaption in domestic lighting. The most common method of generating an LED-based light bulb is through the combination of an LED and an inorganic phosphor which is a rare-earth substituted host structure that absorbs and emits light. In a phosphor converted-LED a phosphor will absorb the blue emission from an LED and re-emit light at longer wavelengths, appearing as white light. This technology can already be seen in many cellphone flashlights. However, this light is very blue tinted and harsh to eye due to the lack of a spectral red component.
The Brgoch group focuses on the development of red, blue and green-emitting inorganic phosphors that when combined with a near-UV LED can produce a full spectrum warm white light that is more pleasing to the human eye. We utilize ab initio density functional theory (DFT) calculations and data-driven approaches in order to narrow the scope of potential phosphor hosts considered by predicting materials properties prior to synthesis. Specifically, DFT will be used to calculate the fundamental properties, e.g. band gap and defect formation energy, of a phosphor to interpret its optical properties. Data-driven approaches such as machine learning, on the other hand, will be used as a predictive tool to identify host structures from large crystal structure databases based on certain desired properties such as high quantum efficiency and good thermal stability. The group also employs numerous synthetic methods including high-temperature sintering, microwave-assisted reactions, and sol-gel chemistry to prepare the phosphors. The characterization involves powder X-ray and neutron diffraction as well as optical spectroscopy.