CAREER: Designing Next-Generation Ultraviolet Light Emission

Nontechnical Description: Ultraviolet (UV) light is a crucial wavelength range for a wide range of technological applications, with important uses in sterilization, sensing, manufacturing, and many others. Relative to traditionally used UV lamps, UV light emitting diodes (LEDs) offer longer lifespan, eliminate the use of mercury, and can have significantly higher power efficiencies. Despite this promise, however, commercially available UV LEDs require a complex fabrication process at high temperatures, significantly increasing manufacturing costs. Further, their efficiency drops off significantly with shorter wavelengths. This combination of high costs, complex fabrication, and low efficiencies at short wavelengths highlights the need to explore material systems capable of remedying those shortcomings. LEDs based on perovskite materials have emerged as promising candidates for next-generation lighting technologies, yet efficiencies from high-energy-emitting materials have remained quite low. This challenge raises our fundamental research question: can the simple, scalable fabrication and high performance of perovskite LEDs be translated into the UV? Doing so would have tremendous impacts on light-emitting technology. We propose to investigate a wide range of perovskite material compositions, guided by theoretical modeling. By relating the underlying material properties to their emissive performance, we will establish design rules for UV material fabrication. We will design electrical contacts to enable charge injection into these materials, controlling the materials within the LED to ensure effective performance. Finally, we will understand the stability of these materials to ensure long-lasting performance towards real impact in a wide range of exciting fields, evidenced with real-world tests. We will build a successful world-class scientific workforce at all career levels through the creation of teaching, mentoring, and outreach programs. The PI will develop a brand-new education series to provide students with hands-on experience at the intersection of photonics, materials, and applications, and will host a local teacher each summer for a hands-on research experience, building connections with the local community and utilizing those teachers as conduits to create long-term engagement programs and partners. Finally, long-term recruitment and culture-building efforts will foster the continued community of the PI’s research group, leading to a more successful and supportive research environment. Technical Description: Ultraviolet light from wide-bandgap (WBG) semiconductor devices is a crucial wavelength range for our society, with important applications ranging from advanced manufacturing to sterilization and purification. Yet modern UV LEDs are complex and expensive to fabricate, and do not have sufficient efficiency far into the UV. We will examine new classes of perovskite and double perovskite materials for their UV-emissive properties, with emissive targets set by improvements on state-of-the-art materials and competitiveness with traditional WBG emitters. Utilizing a model-guided, combinatorial fabrication approach, we will understand the underlying chemistry, materials science, and device physics to enable robust UV emission with simple fabrication. We will identify the key role of charge transport layers to elucidate their role in emissive performance and stability. Finally, we will investigate the roles that material composition, device design, and external conditions have on stability to identify and eliminate the degradation mechanisms limiting devices, and measure the resulting materials for their efficacy in real-world conditions. By bringing new materials, fabrication techniques, and device structures into the fold, this work holds the potential to open new avenues for WBG materials and devices. These learnings will be directly applicable not only to the UV LED field, but to LEDs, lasers, photovoltaics, NSF Award ID: 2541252 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Daniel Congreve | Institution: Stanford University, STANFORD, CA | Award Amount: $550,000 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2541252 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2541252.html