LED innovation offers bright future for lighting

Researchers develop organic phosphorescents that could dramatically reduce cost of LEDs

by Andrew Brister –

A member of the team working on the phosphorescent LEDs, courtesy of Joseph Xu, Michigan Engineering Communications and MarketingResearchers at the University of Michigan (UoM) are in the process of developing a range of phosphorescent LEDs that are relatively inexpensive and simple to produce.

Incandescent lamps turn only 5% of the electricity they use into light, while fluorescent LEDs can produce light from 25% of the electrons that pass through them. Phosphorescent LEDs offer the potential to turn every electron into a ray of light, however, the materials that are typically used to make phosphorescents can be costly.

LEDs are semiconductors that produce light when an electric current runs through them. Organic semiconductors are much cheaper than inorganic semiconductors, but today’s organic technologies rely on specific metals in the semiconductor to enable phosphorescence. This increases the price and sometimes the toxicity of the material.

Now, a team of researchers at UoM led by professor of materials science and engineering, Jinsang Kim, have developed a range of bright, metal-free, organic phosphorescent LEDs.

Organic semiconductors, if left to their own devices, fritter away 75% of the energy that might produce phosphorescence. Instead of light, they generate vibrations in surrounding molecules, thereby heating the material. Incorporating metals can improve phosphorescence, but going metal-free requires a new solution.

“That’s why phosphorescence from metal-free organic materials in nature is very rare,” explained Min Sang Kwon, a materials science and engineering postdoctoral scholar in Kim’s team. A well-known example is the Hope Diamond. Though famously blue, the diamond glows red after exposure to ultraviolet light. Traces of boron in its carbon structure are thought to produce both the blue colour and the phosphorescence.

Kim and his team have demonstrated that the crystal approach works for their all-organic light emitters. The stiff lattice structure stifles vibrations, allowing more energy to be released as light. The team’s crystals produced light from 55% of the charges, but it is difficult to consistently produce high quality crystals in manufacturing.

Instead, the group are looking into how to provide rigidity with less effort. They have tweaked the design of the molecules so that they form structural bonds with a transparent polymer, similar to the way magnets snap together.

The team heated and dried a solution containing the newly-devised light emitters and polymers, and the molecules self-assembled into a stiff matrix. This design allowed 24% of the charges to produce light. Whilst this is only as good as the output of fluorescent LEDs, the team is working to further improve the efficiency. For more, visit: www.oled-info.com

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About steve@bayintegratedmarketing.com

Steve Ulrich is a principal at Bay Integrated Marketing: www.bayintegratedmarketing.com. I have been working with people to maximize their use of social media and internet publishing, optimize their websites to turn prospects into customers, and establish their personal brand on the internet. We are also working with Eco Distribution, Inc. to find and implement practical solutions to help clean up our air and the environment. Eco Distribution, Inc. is a California based Distributor and Representative Firm dealing in environmentally friendly and Green solutions. We have leveraged 30 years experience in responsible construction management to provide solutions for some of the most impactful challenges facing our air, water, and land. We have an oil/hydrocarbon remediation system that is effective on everything from simple oil stains on a driveway, to complex oil disasters in the ocean. My approach to social media and internet marketing is simple. Instead of spending a fortune “buying” keywords and ads that don’t return anything we concentrate on three areas: I CAN GET YOU FOUND ON LINKEDIN - NUMBER ONE, PAGE ONE.
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