The new prototype LED bulb emits less of that annoying blue light

Being more efficient, traditional LED bulbs require much less electricity to operate. But they are not without problems.

LED bulbs offer considerable advantages over other types of lighting. Being more efficient, they require much less electricity to operate. They don’t give off unwanted heat like old-fashioned incandescent bulbs do, and the best of them last a long time even at fluorescent bulbs.

But LEDs are not without their problems. Questions persist about the alleged links between health problems such as fatigue, mood disturbances and insomnia due to overexposure to the bluish light produced by today’s standard LED bulbs. Additionally, higher prices may cause bulb buyers to weigh other options.

A University of Houston research team led by Jakoah Brgoch, associate professor of chemistry at the College of Natural Sciences and Mathematics and principal investigator at the Texas Center for Superconductivity, is developing an LED bulb that emits most of its energy from the safer purple segment of the visible light spectrum. Instead of just masking blue light, they develop a unique class of luminescent materials called phosphors that absorb the single-color emission of a purple LED and convert the light to cover the majority of the visible spectrum.

Jakoah Brgoch and Shruti Hariyani

University of Houston Professor Jakoah Brgoch watches graduate research assistant Shruti Hariyani adjust a phosphorus sample for the lab’s radio frequency oven. Credit: University of Houston

“Our group creates phosphors that work, not with the conventional blue LED chip that almost all LED bulbs use today, but with a purple LED chip. It basically changes from blue to purple as a base source and then converts the purple LED light into the broad spectrum white light that we see, ”explained Brgoch. “Our ultimate goal is for this new purple-based bulb to be as energy efficient as possible and as inexpensive, ultimately making the new lighting technology marketable for consumers. “

The results of their research were recently published in Applied materials and interfaces ACS, a journal of the American Chemical Society.

At this point, you might be looking at your favorite lamp’s standard LED bulb and find its white light to be perfect. But technically speaking, there is no such thing as pure white light.

Hold a prism up to this bulb, and you will see its light separated into wavelengths which show a nice range of color bands from purple to red; this is what scientists call the visible spectrum of light. (If your prism isn’t practical, then imagine having your own little rainbow. It would look a lot.)

The light from your lamp looks white because your eyes and brain are working together to blend the human perception of these separate bands of color into a white light that can then illuminate the words you read. Different types of bulbs emphasize different parts of the visible spectrum of light.

Engineers in lighting companies manipulate the balance to create a specific ambience. A little more red gives a warm, soft white light that is nice in a living room, while cool blue tones give a crisp white light better for office lighting. But outside of the lab, the LED trend towards blue has been hard to avoid.

“Sometimes you recognize it – these are the cheapest LED bulbs. And then sometimes it looks like a nice warm white light. But even in the more expensive bulbs, if they are based on a blue LED, there is still a significant component of blue light sneaking in, ”explained the professor.

Lately, scientists have focused on how light frequencies affect health.

“With the advent of LED lighting, companies began to try to understand how humans interact with light and, more importantly, how light interacts with humans,” said Brgoch. “When you’re sitting in your office, the blue hues in your light are good because they help you stay alert. But that same light at night can keep you awake. It is the balance that must be found. It is about following a natural circadian cycle without interruption.

Sleep studies show that overexposure to blue frequencies at night can alter hormones like melatonin, sometimes leading to insomnia, disrupted sleep cycles, and other problems. Too much exposure to blue light is also suspected in cataract formation. Interestingly, city dwellers living amid LED street lights, traffic lights, and illuminated commercial signs are exposed to more LED exposure day and night than commuters.

“That doesn’t mean we should just get all blue light out of your bulbs. You need part of the blue spectrum. It’s not about eliminating the blue, it’s about keeping it at a reasonable level. This is what we are looking for with our work, ”said Shruti Hariyani, graduate research assistant, author of the article.

Back in the lab, Brgoch and his team focus on identifying phosphors and finding which ones are most feasible, in terms of energy efficiency and economy, to move on to prototype bulbs. “We’re looking to find new materials as a way to help lower the cost of these lights as well. Each time you have more materials available, the patent licensing costs go down, making the bulbs less expensive. So that’s one of our driving forces, ”said Brgoch.

In the quest for what Hariyani calls human light, the research team is testing these potential materials.

“Hear me say, ‘this is different, this is new’ when we find the right phosphorus that can pair with purple – I guess this is my Eureka moment,” she said.

For research not directly related to the LED project, Brgoch and Hariyani were recently awarded the 2021 Materials Chemistry and Best Paper Award. The award, presented by the Inorganic Chemistry Division of the American Chemical Society, recognizes outstanding influence in the field of materials chemistry and the recognition of research as a team effort.

Reference: “Advancement of Human-Centered LED Lighting Using Na2MgPO4F: EU2+»By Shruti Hariyani and Jakoah Brgoch, March 30, 2021, Applied materials and interfaces ACS.
DOI: 10.1021 / acsami.1c00909

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