Nav: Home

New technique could pave the way for simple color tuning of LED bulbs

April 29, 2019

A new technique?the result of an international collaboration of scientists from Lehigh University, West Chester University, Osaka University and the University of Amsterdam?could pave the way for monolithic integration for simple color tuning of a light bulb, according to Volkmar Dierolf, Distinguished Professor and Chair of Lehigh's Department of Physics who worked on the project.

"This work could make it possible to tune between bright white and more comfortable warmer colors in commercial LEDs," says Dierolf.

The team demonstrated the possibility of color tuning Gallium Nitride (GaN)-based GaN LEDs simply by changing the time sequence at which the operation current is provided to the device. Light-emitting diodes or LEDs are semiconductor devices that emit light when an electric current is passed through it. Notably, the technique is compatible with current LEDs that are at the core of commercial solid state LED lighting.

The work is described in an article published online in ACS Photonics called "Color-Tunablility in GaN LEDs Based on Atomic Emission Manipulation under Current Injection." The lead author, Brandon Mitchell, is a former graduate student in Dierolf's lab, now an assistant professor in the Department of Physics and Engineering at West Chester University in Pennsylvania.

In today's active LED displays, different colors are produced by three to four individual LEDs that are placed close to each other and create the different fundamental colors needed to produce the full color spectrum.

"We demonstrate that this can be achieved by a single LED." says Dierolf. "We show that is possible to attain red, green and blue emissions originating from just one GaN LED-structure that uses doping with a single type of rare earth ion, Europium (Eu). Using intentional co-doping and energy-transfer engineering, we show that all three primary colors can emit due to emission originating from two different excited states of the same Eu3+ ion (~620 nm and ~545nm) mixed with near band edge emission from GaN centered at ~430nm. The intensity ratios of these transitions can be controlled by choosing the current injection conditions such as injection current density and duty cycle under pulsed current injection."

In other words, the team achieved color-tunability in a single GaN-based LED through the manipulation of the emission properties of an atomic-type dopant.

Mitchell pointed out that "The main idea of this work - the simultaneous active exploitation of multiple excited states of the same dopant - is not limited to the GaN:Eu system, but is more general. The presented results could open up a whole new field of tunable emission of colors from a single dopant in semiconductors, which can be reached by simple injection current tuning."

According to Dierolf, this research may benefit those who are looking for more comfortable "warmer" white light from LEDs.

"It could pave the way for monolithic integration for simple color tuning of a light bulb," adds Dierolf. "It would also be beneficial for micro-LED displays, since it allows for higher density of pixels."

The materials used in previous research on color tunable LEDs did not allow for easy integration with current LED technology, he adds. This work is compatible with current GaN-based LEDs that are at the core of commercial solid state LED lighting.
-end-


Lehigh University

Related Color Articles:

Building a better color vision test for animals
University of Cincinnati biologists modified simple electronics to create a color vision test for fiddler crabs and other animals.
Defects add color to quantum systems
Researchers are investigating light-emitting defects in materials that may someday form the basis of quantum-based technologies, such as quantum computers, quantum networks or engines that run on light.
The color of your clothing can impact wildlife
Your choice of clothing could affect the behavioral habits of wildlife around you, according to a study conducted by a team of researchers, including faculty at Binghamton University, State University of New York.
Recovering color images from scattered light
Engineers at Duke University have developed a method for extracting a color image from a single exposure of light scattered through a mostly opaque material.
Deciphering how the brain encodes color and shape
There are hundreds of thousands of distinct colors and shapes that a person can distinguish visually, but how does the brain process all of this information?
Fish-inspired material changes color using nanocolumns
Inspired by the flashing colors of the neon tetra fish, researchers have developed a technique for changing the color of a material by manipulating the orientation of nanostructured columns in the material.
Iridescent color from clear droplets
Under the right conditions, ordinary clear water droplets on a transparent surface can produce brilliant colors, without the addition of inks or dyes.
Comparing antioxidants levels in tomatoes of different color
Greater levels of specific antioxidants were associated with particular colorations of tomato fruit.
Turning a porous material's color on and off with acid
Stable, color-changing compound shows potential for electronics, sensors and gas storage.
Color coded -- matching taste with color
Color can impact the taste of food, and our experiences and expectations can affect how we taste food, according to Penn State researchers, who suggest this may have implications for how food and beverage industries should market their products.
More Color News and Color Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.