Industry News




 

01/18/2013

LED: New Material, New Possibilities?

 
New possibilies for LED lighting may make the technology more applicable to traditional lighting applications.

Heard about FIPEL?  Well, it looks like LED may have new possibilities as well.  LEDs are known for their energy efficiency and durability, but the bluish, cold light of current white LEDs has precluded their widespread use for indoor lighting.

Now, University of Georgia scientists have fabricated what is thought to be the world's first LED that emits a warm white light using a single light emitting material, or phosphor, with a single emitting center for illumination. The material is described in detail in the current edition of the Nature Publishing Group journal "Light: Science and Applications."

"Right now, white LEDs are mainly used in flashlights and in automotive lamps, but they give off a bluish, cool light that people tend to dislike, especially in indoor lighting," says senior author Zhengwei Pan, an associate professor in the department of physics in the UGA Franklin College of Arts and Sciences and in the College of Engineering. "Our material achieves a warm color temperature while at the same time giving highly accurate color rendition, which is something no single-phosphor-converted LED has ever been shown to do."

Two main variables are used to assess the quality of artificial light, Pan explained. Correlated color temperature measures the coolness or warmth of a light, and temperatures of less than 4,000 kelvins are ideal for indoor lighting.

Correlated color temperatures above 5,000 kelvins, on the other hand, give off the bluish color that white LEDs are known for. The other important measure, color rendition, is the ability of a light source to replicate natural light. A value of more than 80 is ideal for indoor lighting, with lower values resulting in colors that don't seem true to life.

The material that Pan and his colleagues fabricated meets both thresholds, with a correlated color temperature of less than 4,000 kelvins and a color rendering index of 85.

Warm white light can commonly be achieved with a blue LED chip coated with light emitting materials, or phosphors, of different emitting colors to create what are called phosphor-based white LEDs, Pan said. Combining the source materials in an exact ratio can be difficult and costly, however, and the resulting color often varies because each of the source materials responds differently to temperature variations.

"The use of a single phosphor solves the problem of color stability because the color quality doesn't change with increasing temperatures," says lead author Xufan Li, a doctoral student in the College of Engineering.

To create the new phosphor, Pan and his team combine minute quantities of europium oxide with aluminum oxide, barium oxide and graphite powders. They then heat the powdered materials at 1,450 degrees Celsius (2,642 degrees Fahrenheit) in a tube furnace. The vacuum of the furnace pulls the vaporized materials onto a substrate, where they are deposited as a yellow luminescent compound. When the yellow luminescent compound is encapsulated in a bulb and illuminated by a blue LED chip, the result is a warm white light.

Although his team's results are promising, Pan emphasized that there are still hurdles to be overcome before the material is used to light homes, businesses and schools. The efficiency of the new material is much lower than that of today's bluish white LEDs. Scaling the production to an industrial scale will be challenging as well, since even slight variations in temperature and pressure in the phosphor synthesis process result in materials with different luminescent colors.

The new yellow phosphor also has a new lattice structure that has not been reported before. The researchers currently are working to discern how the ions in the compound are arranged in hopes that a better understanding of the compound at an atomic level will allow them to improve its efficiency.

"We still have more work to do," Pan says, "but the color temperature and rendition that we have achieved gives us a very good starting point."

 


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Visit our website today to learn about the design flexibility of a Morton building and the endless possibilities of partnering with our designBUILD team.


Wood construction is both cost and energy efficient. Check out Morton Buildings and our designBUILD team online today to discover all the benefits of post-frame construction.


When choosing a metal-clad building for your next construction project, consider Morton Buildings, Inc., and their designBUILD team, we’ll make your dream a reality.

We Can Help You Reduce Energy by 30%

Our mission is to help our customers manage their buildings' energy costs, improve reliability, and enhance performance while having a positive impact on the environment.
CLICK HERE to find out how.

 


Tennant Company is a recognized leader in designing, manufacturing and marketing solutions that help create a cleaner, safer, healthier world. With thousands of satisfied customers already using award winning ec-H2O technology, why not see what you're missing? Test ec-H2O on your soils in your facility. Get a free demo.


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10/20/2014

The EPA looks to help improve energy and air quality during educational facility renovations. 

10/17/2014

Agency says current regulations "don't protect worker health".

10/16/2014

Scientists have developed LED bulbs free of rare earth metals.

10/15/2014

Survey shows a decrease in employees coming to work sick.

10/14/2014

New efficiency ratings available for apartment units

10/10/2014

New code to increase commercial building efficiency.

10/09/2014

Take charge of your electricity bill with these quick tips.

10/08/2014

Illumination improvements take the top award for physics

10/07/2014

Study shows equipment improvements could boost efficiency. 

10/06/2014

New device integrates batteries into solar cell design.

10/03/2014

The switch to green products comes to healthcare facilities.

10/01/2014

Photovoltaic installations serve nearly 2.7 million students

09/30/2014

Incidence of fires and property loss down from 2012

09/29/2014

Academic achievement tied to responsible reporting habits

09/26/2014

Survey shows people more careful, less satisfied in public washrooms.

09/25/2014

A new study shows that switching natural gas for coal will not significantly reduce the amount of CO2 emissions being produced. 

09/24/2014

A new study shows the carbon emission reduction policies individual states have adopted are yielding results.

09/23/2014

A recent survey of industry professionals indicates that investment in energy efficiency projects will increase over the next year.

09/22/2014

Fort Carson in Colorado is well on its way to reaching the goal of net-zero energy by 2020. 

09/19/2014

New regulations from the DOE would improve commercial air conditioner efficiency by as much as 30%. 

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