Human-Centric Lighting: Rare-Earth-Free Photoluminescent Materials for Correlated Color Temperature Tunable White LEDs

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Summary

This paper demonstrates that organic photoluminescent dyes (Coumarin 6 and Nile Red) can replace rare-earth phosphors in white LEDs to produce dynamically tunable correlated color temperatures, supporting human-centric lighting design. The resulting LEDs achieve a wide CCT range suitable for mimicking natural daylight progression, which is critical for avoiding circadian disruption in built environments.

Key Findings

CCT values ranging from 2975 K (warm, evening-appropriate) to 6261 K (cool, daytime-appropriate) were achieved using two organic dyes in a remote phosphor multilayer configuration.
Color Rendering Index (CRI) values exceeded 80 across the tunable range, preserving light quality suitable for human-centric applications.
A blue LED chip was used as the excitation source, with Coumarin 6 and Nile Red embedded in flexible spectral converter layers — the first demonstration of this approach for human-centric lighting.

Categories

Sleep & Circadian Health: The paper addresses circadian disruption from artificial lighting and proposes tunable CCT LEDs to mimic natural light dynamics throughout the day.

The Science of Light: The paper presents technical development of rare-earth-free WLEDs with tunable correlated color temperature and quantified light quality metrics relevant to circadian-supportive lighting standards.