© Wei Ding
Chou's solar panel can trap light more efficiently and reduce reflection by utilizing a nanomesh.
A new method for creating solar panels using nanotechnology can double or triple their efficiency in capturing and converting light to electricity. The new nanotechnology was developed by a research group led by electrical engineering professor Stephen Chou and has the potential to significantly improve the performance of organic solar panels used to generate renewable energy.
The key mechanism behind the success of the solar panels is a manufacturing technique called “nanoimprint lithography” invented by Chou 16 years ago. Whereas traditional techniques require expensive chemical reactions, Chou explained that his method uses mechanical processes to deform the panel’s active layer, the layer that is responsible for capturing light, into a desired pattern.
As a result, nanoimprinting reduces the time of manufacturing by several-fold. It is also easier to perform on a large scale, as well as simpler and cheaper than existing techniques. In 2003, Chou’s technology was selected as one of the MIT Technology Review’s “10 Emerging Technologies that Will Change the World.”
“At the time, it was absolutely crazy because people for many, many years always used light,” Chou said. “Now the imprint became a well-accepted technology for manufacturing.”
In the new solar cells, which are detailed in a paper coauthored by Chou and electrical engineering graduate student Wei Ding this past November, the thin upper active layer is composed of a metal mesh of nano-size holes instead of the traditional indium tin oxide films, which are made of an expensive and rare material. In comparison, the new cells’ active layer can be made of conducting metals such as copper or gold, according to Chou.
The application of nanoimprint technology to solar panels is able to increase both the panels’ light absorption and light retention. Whereas 20 to 50 percent of the light that hits a traditional solar panel is reflected and consequently lost, only five percent of incoming light reflects off the new solar panel, Ding said. Furthermore, due to new physical interactions that happen in the metallic nanostructures, Chou explained that the new panels are equally efficient in collecting indirect sunlight as light that directly hits the panel’s surface.
The next step to implementing the new technology in solar panels is to develop tools that can perform nanoimprint manufacturing on a large scale, a development that Chou has compared to inventing the printing press. Although his group is not actively working to commercialize the new panels, Chou said he believes that they will be utilized in the future. The deciding factor for their implementation will be future government policies and whether they encourage outside investment in the technology.
“From the technology side, I believe that our development, many parts of it, will be used for the next generation of solar cells,” Chou said.
“It is very promising in the future because it is relatively cheap,” Ding added. “I think it can happen within five years.”
The development that Chou and his group have put forth is regarded as a significant advancement for the field of renewable energy, according to mechanical and aerospace engineering and applied and computational mathematics professor Emily Carter.
“These kinds of innovations are critical to improving the efficiency of organic solar cells. It could potentially be transformative,” Carter, who is also the director of the Andlinger Center for Energy and the Environment, explained. “The fact that he can essentially capture all the light is extremely promising”
Chou and Ding are currently working on applying the nanotechnology to a variety of materials in order to continue increasing the efficiency of organic solar cells.
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