Image via Michael Geminder

Scientists have developed energy efficient, ultra-thin light-emitting diodes (LEDs) for next-generation communication technologies.

Light sources that reliably convert electrical to optical signals are of fundamental importance to information processing technologies. Energy-efficient and high-speed LEDs that can be integrated onto a microchip and transmit information are one of the key elements in enabling high volume data communication.

Two-dimensional (2D) semiconductors, graphene-like, atomically thin materials, have recently attracted significant interest due to their size (just a few atoms thick), well-defined light emission properties, and their prospects for on-chip integration. While, in recent years, researchers have succeeded in fabricating LEDs based on these materials, realizing efficient light emission has remained a challenge.

An efficient LED device converts most of its electrical power input into light emission (i.e., with minimal losses due to conversion into other forms of energy such as heat). Previous studies on LEDs based on 2D semiconductors reported that a large amount of electrical current is needed to trigger light emission. This means that a substantial fraction of the input electrical power is dissipated as heat instead of generating light.

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An interview with Isamu Akasaki

On June 8, 2016, Yue Kuo, an ECS fellow and vice president of The Electrochemical Society, traveled to the Akasaki Institute at Nagoya University in Japan to talk with Isamu Akasaki, a Nobel Prize winner and ECS life member.

Professor Akasaki is a materials scientist specializing in semiconductor science and technology. He is a pioneer of efficient blue light-emitting diodes which have enabled bright and energy-saving white light sources. He shares the 2014 Nobel Prize in Physics with Hiroshi Amano and Shuji Nakamura for this work. Prior to their groundbreaking work, scientists had produced LEDs that emitted red or yellow-green light, but not blue. Blue had been thought impossible or impractical to make. Blue LEDs became commercially available in 1994.

The new combination of blue, green, and red LEDs produces white light, and blue LEDs coated with YAG:Ce yellow phosphor appear white to the eye and can be developed for much less energy than that from incandescent and fluorescent lamps, which contain toxic mercury. Prof. Akasaki’s work helped lead to the development of blue semiconductor lasers, which proved useful for high-capacity optical-media devices such as Blu-ray disc players.

What follows is an edited transcript of the conversation between Yue Kuo and Isamu Akasaki, which they had in English.

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When examining climate change and energy conservation, minds often tend toward large-scale grid technologies. While solar technologies and energy storage systems are big end goals, researcher from Iowa State University state that there are intermittent steps that should be considered.

“Many people consider energy efficiency to be the low-hanging fruit,” says Yu Wang, who studies global energy policy and energy efficiency at Iowa State University. “If you’re facing the target of trying to mitigate climate change, energy efficiency should be the first choice because it’s cheap and easy in comparison with other options.”

Importance of Energy Conservation

For Wang and others, replacing old incandescent bulbs with LED lighting is an important step in energy conservation. While it may seem like a move this small would have no impact on the overall energy consumption of the country, Wang and other researchers estimate the swap could yield an electrical savings of 10.2 percent by 2035.

Another step toward a more energy efficiency society deals with policy at all levels.

“In general [the future of renewable energy] is really up to the politicians to change the energy infrastructure,” says John A. Turner, National Renewable Energy Laboratory. “We have pretty much all the technologies we need. We certainly need to be able to upscale them and get things cheaper, but the issue is how do you replace an essentially established infrastructure with a new one? You need political support.”

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Research and improvements in LED technology have impacted everything from television screens to life-changing electronic vision. With the vast potential of LED technology, scientists are looking to improve the efficiency of LEDs as well as simplify the manufacturing process.

A team at the California Nanosystems Institute at UCLA is focusing on the science of electroluminescence to accomplish this by demonstrating this process from multilayer molybdenum disulfide.

In the new study, UCLA’s Xianfeng Duan was able to show that the multilayer molybdenum disulfide—the relatively cheap and easy to produce material—can, contrary to popular belief, show strong luminescence qualities when electrical current passes through.

Prior to focusing his attention on building better LEDs, Duan focused his research efforts on topics such as graphene’s applications in transistors and applying nanoscale materials to solar energy efforts.

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The editors of the ECS Journal of Solid State Science and Technology are calling for papers for the upcoming focus issue: Novel Applications of Luminescent Optical Materials.

Submission Deadline: July 15, 2015

Submit your manuscript today!

The research landscape of luminescent and optical materials is rapidly changing due to a need for such materials outside the lighting and display technologies. Novel materials are needed and are developed with luminescent and optical properties appropriately tuned for applications in solar cells, sensors, bio-imaging, light extraction, and related opto-electronics in addition to solid state lighting and display technologies.

Find out more.

Read previous focus issues in ECS journals.

Intel may be known for microprocessors and long-time ECS member Gordon E. Moore, but now the company’s Edison technology is lending itself to something entirely different.

They call it the Spider Dress, and the innovation involved in making this product goes far beyond sheer aesthetic value.

The 3-D printed dress was created by Anouk Wipprecht and uses Intel’s Edison technology to power robotic spider legs surrounding the collar, designed to keep people out of your personal space.

The dress’s robotic arms are connected to proximity sensors, which will react when someone gets too close to the wearer of the dress. Further, the sensors use biometric signals to measure the wearer’s stress level, which allow the dress to respond based on your mood.

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Researchers from the University of Sydney have recently published their findings that quantum dots made of graphene can improve bio-imaging and LEDs.

The study was published in the journal Nanoscale, where the scientists detailed how activating graphene quantum dots produced a dot that would shine nearly five times bright than the conventional equivalent.

Essentially, the dots are nano-sized semiconductors, which are fluorescent due to their surface properties. However, this study introduces the utilization of graphene in the quantum dot, which produces an extra-bright dot that has the potential to help medicine.

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More and more households are using LED light bulbs due to improved efficiency, reliability, and now a more affordable cost over their incandescent cousins. With droves of scientists researching in the area of LED and producing new developments, these bulbs are beginning to become the new norm.

Let’s take a look at the journey the LED bulb has gone though thus far.

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