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