Naturally Derived Organic Dyes for LED Lightings of High Color Rendering and Fidelity Index

Light-emitting diodes (LEDs) are a lighting technology with a huge and ascending market. Typically, LED backlights are often paired with inorganic phosphors made from rare-earth elements (REEs) to tune the emission lineshapes for different applications. However, REE production is a resource-intensive process with many negative environmental impacts. Herein organic hybrid LEDs are developed using organic dyes synthesized from an abundant and non-toxic natural product (theobromine) to replace REE phosphors. The resulted hybrid LED generates continuous emission from 400-740 nm, resulting in a high color rendering index (the current industry standard) of 90 and a color fidelity index (the most advanced and comprehensive standard) of 92, challenging commercial LEDs based on REE phosphors. In addition, the light-converting composite is made from 99 wt% SBS, an inexpensive industrial polymer, and 1 wt% theobromine dyes, reducing the cost of the light converter to (sic)1.30 for a 1 W LED, compared to approximately (sic) 19.2 of commercial products. The light converting efficiency of the dye-SBS composite is 82%. Excited state kinetics experiments are also conducted to provide guidance to further increase the light-converting efficiency of the theobromine dyes while maintaining excellent color rendering and fidelity.