Redefining artificial lighting through spectral engineering of light sources for well-being

Area of Science:

• Lighting Science
• Materials Science
• Human Health

Background:

• Artificial lighting, particularly light-emitting diodes (LEDs), has advanced illumination but can lead to detrimental health effects due to insufficient natural light exposure.
• Human-centric lighting necessitates visual quality and circadian performance that replicate the dynamic spectral power distribution (SPD) of natural daylight.

Purpose of the Study:

• To develop a color-tunable LED-based light source capable of achieving spectral power distributions (SPDs) similar to daylight and incandescent lighting.
• To establish new metrics for quantifying the similarity between artificial light sources and reference daylight spectra, considering both visual and circadian effects.

Main Methods:

• Fabrication of a hybrid light source using additive manufacturing, incorporating dyes with thermally activated delayed fluorescence (TADF) in light converter channels.
• Photoexcitation of TADF dyes using violet-emitting LEDs (VLEDs) to achieve tunable color output.
• Evaluation of the light source's performance using Illuminating Engineering Society (IES) color gamut index (R_g) and color fidelity index (R_f), and proposed efficiency metrics for benchmarking.

Main Results:

• The developed light source closely approximates daylight SPDs, achieving IES R_g values within 3% and R_f values within 7% across a wide correlated color temperature (CCT) range (4277 K to 22,333 K).
• Proposed efficiency metrics demonstrated that circadian lighting performance remained within 10% over the same CCT range.
• The hybrid light source sets a new benchmark for artificial lighting in approximating daylight characteristics.

Conclusions:

• This color-tunable LED light source offers a significant advancement in artificial lighting, effectively mimicking daylight's SPD for enhanced visual and circadian benefits.
• The proposed efficiency metrics provide a robust method for evaluating and benchmarking WLEDs (white light-emitting diodes) against daylight spectra.
• The findings contribute to addressing the dual challenges of human health and sustainability in lighting technology.