The concept of human-centric lighting stems from the evolution of sunlight’s intensity and color temperature throughout the course of a day. This natural progression of bright cold-white light during the middle of the day to a softer warm-white light in the evening stimulates intrinsic photosensitive retinal ganglion cells that control our circadian rhythm. The blue-hue of daylight activates these cells to produce dopamine and cortisol while suppressing melatonin, the sleep hormone, to keep humans awake and alert. The current generation of energy-efficient LED lights reproduce daylight by converting a blue-emitting LED into a broad-spectrum white light using inorganic phosphors. Unfortunately, the resulting intense blue-hue generated by cheap LED bulbs and the underlying blue light from even the most expensive bulbs have been shown to cause macular degeneration, cataract formation, mood disorders, and circadian disruption, resulting in insomnia and fatigue. This talk will investigate alternative solutions to reduce the amount of blue light generated by modern LED lights. The core change will require identifying new luminescent phosphors that pair with violet-emitting LED chips while still producing high-quality white light. As a result, we have been developing materials like blue-emitting Na2MgPO4F:Eu2+ and K3AlP3O9N:Eu2+, and the green-emitting NaBaB9O15:Eu2+ that meet all of the necessary requirements, including a high quantum yield, thermally robust emission, and strong violet absorption. Incorporating these materials into prototype devices demonstrates that it is possible to produce a warm-white light with a higher color rendering index than a commercially purchased LED light bulb while significantly reducing the blue component.

Advancing human-centric lighting with phosphor converted violet LEDs

ACS Fall 2021

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