We've told you how plastic can become fuel and form flexible batteries and transparent solar cells. Now, Wake Forest University scientists have created a new type of lighting made from thin layers of light-emitting polymer combined with nanomaterials that glow.
Based on alternating current (AC) field-induced polymer electroluminescent (FIPEL), the lighting device emits a soft, white light, unlike the harsh light from either fluorescents or LEDs. The light is similar to sunlight, and also flicker-free. The device itself is shatter-proof, avoiding broken glass and the hazardous mercury contained in compact fluorescent (CFL) bulbs.
Wake Forest University scientists have devised a shatterproof, white light, flicker-free lighting device based on field-induced polymer electroluminescent (FIPEL) technology. (Source: Wake Forest University)
The new lighting devices are also long-lasting, said David Carroll, professor of physics and director of the university's Center for Nanotechnology and Molecular Materials, in a press release. He owns one that has worked for about 10 years. The device has about the same efficiency as LEDs and is twice as efficient as CFLs. In addition to applications in office and home lighting, Carroll envisions the technology being used in large display lighting, such as signs on buses and subway cars, as well as store marquees.
The research team, which Carroll heads, made the lighting device from three layers of moldable, light-emitting polymer. Multi-walled carbon nanotubes (MWNTs) are dispersed in the active layer's polymer, sandwiched between two dielectric layers. The team described its work in an article in Organic Electronics.
According to the article:
An asymmetric device structure, using one dielectric layer, was used to study band alignment effects of carbon nanotubes in charge injection from a contact. The presence of MWNTs within the emissive layer facilitates effective internal charge generation in the symmetric devices, as would be expected if they acted as a charge source. The MWNTs effectively doped the polymer, modifying energy level alignment in the device and increasing field-induced polarization currents. Increase in light emission of five times is achieved in composite devices compared with the device without MWNTs.
The device is inexpensive to make, and the materials can be formed into many shapes and colors, from regular bulbs that fit household lamp and fixture sockets, to large 2-feet x 4-feet panels for office lighting. The team is working with a company to commercialize and manufacture the technology, and Carroll expects it to be available sometime this year.
Ann, it seems that usage of plastic is increasing in various forms across different domains. Some of the good qualities of plastics like resistance to corrosion, low electric & thermal conductivity, durability etc can make them more adaptable and suitable for such missions.
Ann, the fact that Carroll has been developing the technology for ten years makes me wonder: What's been the big technological hurdle in all that time?
Thanks, mrdon, glad you liked the article. We give links in the blog to a detailed journal article that may have the info you're looking for. Regarding SSL, this technology doesn't sound like it qualifies.
Ann, What a great article. Given the tremendous luminance output and efficiency of FIPEL and its applications for commerical and residential lighting, what happens to the lonely LED? I'm curious to know the thermal capabilities, in terms of watts, and how it stacks against high bright LEDs. I've worked on LED projects for automotive and residential lighting applications and the biggest challenged I had was thermal management of the LEDs and the switching mode power supplies. Also, to put a solid state lighting (SSL) product out on the market requires a tremendous amount of testing (6000hrs) to be Energy Star and DOE compliant per the SSL LM80 testing document. Once the SSL product meets the LM80 requirements, its ready to be a saleable consumer item for purchasing.
Yes, I did wonder about that, Ann...if the material was so specialized that perhaps recycled plastic is not an option. Maybe down the line this could work but as you point out, we're definitely not there yet--which is a shame, because there is so much plastic in the world that goes to waste!
Thanks for the great information Ann - just goes to show how we take for granted things outside of our areas of expertise...that's what I love about this forum, it's a great way to learn from others. Makes perfect sense now that you've pointed it out...and a great idea about multiple waste streams fro recycled material. The logistical complexity would be huge but the payoff would be enormous.
It would be great if recycled plastic could be used in devices such as this, but I think it's unlikely that will happen anytime soon. The plastic used in this device is a highly customized and engineered material, which is why it can do what it does. And plastics are not monolithic: they differ greatly in their ability to be recycled into something usable, and the vast majority of available recycled plastic in the US is still of only 1 or 2 types, as we discuss here
http://www.designnews.com/author.asp?section_id=1392&doc_id=242808
and here
http://www.designnews.com/author.asp?section_id=1392&doc_id=240409
Perhaps in the future we'll have an existing, functional infrastructure with multiple known waste streams, so the specific recycled material a manufacturer needs is as easily obtainable as buying virgin plastic. But we're not there yet.
Maybe we're all used to Silicon Valley-style announcements of new technology for sale right now in high volumes, and not of the long R&D cycle behind that technology. In materials technology, especially energy-related, development can take a long time. Thanks, William, for finding those cost figures. The main researcher has had a single working device for a long time--but not a bulb, and, presumably, a very expensive device, and, I'd guess, one he's been tinkering with as a prototype.
With LEDs dropping in price virtually every year, automakers have begun employing them, not only on luxury vehicles, but on entry-level models, as well.
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