Lighting home and commercial buildings in the US account for 6% of the total US electrical energy use and 15% of the total electrical energy expenditure, which translates to $50 billion per year. There is an outstanding opportunity to reduce this cost by replacing current incandescent and fluorescent lighting with white light emitting diodes (LEDs). However, the color quality and efficiency must be improved further. These LED-based light bulbs produce white light by using a luminescent powder called a phosphor, coating on top of a near-ultraviolet (UV) or blue-emitting LED chip. The phosphor is a key component in these devices because it is critical for the overall efficiency and color of these bulbs; unfortunately, there are only a few viable phosphors available for this application today. Therefore, it is prudent to discover new phosphor systems to fully realize the conversion to new efficient lighting. The researchers are addressing this challenge by developing computational and data-driven methods to predict the properties of phosphors. This approach allows the directed discovery of new phosphors with enhanced optical response. This grant also supports extensive scientific education including sponsoring numerous research opportunities for high school and undergraduate students. These students, mostly from underrepresented groups, are learning how to synthesize and characterize phosphors as well as the importance of this energy-efficient technology. The graduate students supported by this work are trained to pursue opportunities in the optoelectronics industry and also across the technology sector where materials science play a crucial role. Finally, the computational products of this research are disseminated through open-source platforms, so all researchers benefit from the scientific developments.
TECHNICAL DETAILS: Replacing a traditional light bulb with an energy-efficient, phosphor converted-light emitting diode is one of the easiest ways to decrease electricity consumption. This goal requires the discovery of new phosphor systems, which convert the nearly monochromatic LED light into a broad spectrum white light, to fully make use of this technology. The phosphors investigated in this project are based on wide band gap materials (hosts) that contain a small amount of activator (rare-earth element). Depending on the host:activator combination, colors across the visible spectrum are obtained. The central hypothesis driving this research is that the quantum efficiency and thermal quenching resistance of a phosphor are related to the local coordination environment of the activator ion. This research employs advanced first-principles calculations, local structure analysis using X-ray and neutron scattering, and data science to establish a quantitative understanding of this relationship. Modeling these properties using computational tools and confirming the predictions through materials synthesis and characterization produces a feedback loop where our research results are improved with each discovery. The outcome is a series of design rules that will lead to the discovery of new phosphors with superior optical properties.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
