CAREER: Rational Engineering of Efficient, Transparent, and Broadband LEDs from Low-Dimensional Ternary Copper Halides

About This Grant

Abstract Title: Developing next-generation transparent and broadband light-emitting diodes from earth-abundant and nontoxic materials for lighting and display applications. Abstract: Light-emitting diodes (LEDs) are increasingly used in households, industries, and automobiles for both lighting and display purposes. Globally, the current LED market is valued at over $70 billion, accounting for more than 50% of the market share. In the United States, household and industrial lighting accounted for ~16% of the total electricity generated in 2017, and LEDs saved around 185 terawatt-hours (TWh) of energy. Therefore, the use of LEDs is projected to increase dramatically in the coming decades. To meet this global demand, there is a need for low-cost, earth-abundant, and non-toxic new materials for LED applications. This CAREER proposal targets the development of efficient LEDs that are cost-effective, stable, non-toxic, earth-abundant, and solution-processable, made from ternary copper halides. The ternary copper halides proposed here exhibit broadband emission with tunable colors across the spectrum, making them more suitable for lighting applications. The proposal aims to understand the underlying mechanism of emission to tune the emission colors for targeted applications rationally. Most importantly, unlike many existing materials, the ternary copper halides exhibit nearly 100% transmittance in the visible region, showcasing great potential for developing transparent LEDs used in emerging technologies such as virtual reality screens, automobile head-up displays, TV screens, and transparent window lighting. The proposed educational and outreach activities train the 4-H youth leaders and K-12 students across the state in fields that intersect robotics and semiconductors. The educational plan is specifically designed to provide students in rural areas of Mississippi with exposure and access to emerging fields. Low-dimensional ternary copper metal halides are advancing rapidly in LEDs due to their exceptional optical properties, including near-unity PLQYs and tunable broadband emission with strong exciton binding energies. Additionally, copper is earth-abundant and non-toxic, and the copper halides are solution-processable and stable to ambient conditions. This proposal aims to develop efficient, broadband, and transparent LEDs that emit various colors using ternary copper halides as emissive layers. High efficiency and tunable emission will be achieved by rationally controlling the carrier concentration in the emissive layer. Concurrently, this proposal seeks to tackle the mechanism of broadband emission in copper halides using state-of-the-art pump-probe X-ray absorption spectroscopy (TR-XAS). Further, the role of electrons/holes in the overall emission will be uncovered by selectively injecting holes into the emissive layer. Finally, this proposal aims to build highly transparent, broadband copper halide LEDs (T-LEDs) due to the high transmittance of copper halides in the visible-NIR region. In addition to the research plan, the proposal outlines a comprehensive educational and outreach plan that targets training students from a younger age in semiconductor electronics and robotics. Several tasks with hands-on experiments are designed to tackle the challenges of current enrollment in materials chemistry and the future need for a skilled workforce in electronics. 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.