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