CAREER: Targeting novel phosphors for the next generation of solid state white lighting

University Of Houston, Houston TX

Investigators

Abstract

Technical Abstract: Replacing a traditional light bulb with an energy-efficient, phosphor converted-light emitting diode (pc-LED) is one of the simplest and most promising methods to dramatically decrease electricity consumption. These devices are conventionally based on blue- (450 nm) or UV- (370-410 nm) emitting light emitting diodes (LEDs) that are coated with a rare-earth substituted inorganic phosphor encapsulated in an optically transparent polymer. In combination, these emissive lights produce a functional and efficient white light. Unfortunately, the availability and variety of inorganic phosphors that are necessary to efficiently convert the LED emission and create white light are limited, which increases the upfront cost of pc-LEDs and inhibits their widespread adoption. The known phosphors are also often thermally insulating oxides or nitrides, which lead to extreme operating temperatures (above 150 Celsius) under LED excitation that can degrade phosphor performance. Consequently, the next generation of pc-LEDs requires the development of new, efficient inorganic phosphors with enhanced thermal properties to reduce their cost and encourage the replacement of traditional light bulbs. This NSF CAREER award project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, establishes a research approach that connects machine learning, computation, and materials synthesis to target new inorganic phosphors with improved thermal response allowing them to operate in extreme environments. The results from each research step feed back into the original machine learning and computational models to improve the accuracy and reliability of the models. Further, this CAREER award is used to enhance the participation rate of undergraduate research at the University of Houston, with a particular focus in engaging underrepresented groups. This includes a newly established "Boot Camp in Computational Chemistry" to provide STEM students, as well as faculty at undergraduate institutions and community colleges in the Houston-area, the opportunity to learn the basics of computational chemistry. Emphasizing the importance of using a computer to understand chemistry, while also providing opportunities for hands-on research, leads to a new generation of STEM graduates who are prepared for a globally competitive workforce. Non-technical Abstract: This NSF CAREER award, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, addresses the global need to develop more efficient light sources to replace conventional incandescent and fluorescent bulbs. In the US alone, lighting accounts for 22% of total electrical energy use, which translates to $50 billion per year spent on lighting, accompanied with 130 million tons of carbon emitted into the atmosphere from fossil fuel plants. Solid state white lighting, which uses a blue-emitting light emitting diode (LEDs) coated with a luminescent powder called a phosphor, has emerged as highly efficient, long-lasting light source capable of replacing incandescent and fluorescent lighting. New LEDs that emit ultraviolet light have recently been recognized as chips that could yield an even better light source. However, to make use of this technology, it is necessary to discover new, efficient phosphor systems that can convert the ultraviolet LED light into white light. This CAREER award's research and education program support Prof. Jakoah Brgoch at the University of Houston to establish new computational and machine-learning techniques that are capable of increasing the rate at which new phosphors can be identified. This information can then be used to direct the Brgoch group's synthesis towards the most promising phosphor systems, whose properties can be analyzed using computational methods to understand the enhanced optical response. This cooperative research approach not only leads to higher performance materials, but it also has the potential to transform the lighting industry by identifying new and improved materials. Further, this award is used to enhance the participation rate of undergraduate research at the University of Houston, with a particular focus in engaging underrepresented groups. The efforts include a newly established "Boot Camp in Computational Chemistry" to provide STEM students, as well as faculty at undergraduate institutions and community colleges in the Houston-area, the opportunity to learn the basics of computational chemistry. Emphasizing the importance of using a computer to understand chemistry, while also providing opportunities for hands-on research, leads to a new generation of STEM graduates who are prepared for a globally competitive workforce. 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.