Blu-Ray Discs Can Improve The Performance Of Solar Cells

Chuck Bednar for redOrbit.com – Your Universe Online
From old Jackie Chan movies to your favorite episodes of Family Guy, the technology works just the same
Just as VHS tapes were replaced by DVDs, which were themselves replaced by Blu-ray discs, something will eventually come along and replace them as well. But when that happens, don’t be too quick to get rid of your old Blu-rays, as new research suggests that they can be repurposed to improve the performance of solar cells.
According to Rachel Feltman of The Washington Post, experts from the Northwestern University found that the patterns etched onto the discs contain nanoscopic pits and grooves that can be used to enhance the light-absorption properties of solar panels. The researchers also found that quasi-random patterns (those that absorb more than one wavelength of light, but not unusable ones) work the best, she added.
“We had a hunch that Blu-ray discs might work for improving solar cells, and, to our delight, we found the existing patterns are already very good,” Jiaxing Huang, an associate professor of materials science and engineering in the university’s McCormick School of Engineering and Applied Science, said in a statement. “It’s as if electrical engineers and computer scientists developing the Blu-ray technology have been subconsciously doing our jobs, too.”
Huang and his colleagues, who published their findings in Tuesday’s edition of the journal Nature Communications, tested a vast array of different movies and TV shows, including action films, dramas, cartoons and documentaries. They found that the content of the discs was irrelevant, and that Jackie Chan movies enhanced light absorption just as well as episodes of “Family Guy.”
“For solar cell applications, we want to enhance light absorption over the entire solar spectrum – wavelengths from about 350 nanometers to 2,300 nanometers,” he added in an interview with Live Science Contributor Charles Q. Choi. Typically, “very expensive fabrication techniques are usually needed to create quasi-random patterns suitable for solar cells,” Choi added, but the new study indicates that using Blu-ray discs make it possible to create these patterns at a fraction of the cost.
The experiments took a few months to conduct, noted Arielle Duhaime-Ross of The Verge, but when all was said and done, the researchers concluded that Blu-rays could be used to produce rubber stamps that could be pressed into polymer solar cells. The resulting patterns, the Northwestern University researchers said, could enhance the overall light absorption properties of solar arrays by 20 percent.
Huang told Duhaime-Ross the discovery was unexpected, and the imprinting process used to produce the rubber stamps still had to be adjusted in order to achieve thicker cells or different types of materials. Once their technique is perfected, however, it could give new life to Blu-ray discs once they are no longer wanted or become obsolete.
Knowing that it worked wasn’t enough, however. The researchers next set out to discover “why” it worked. To do so, they closely analyzed the data processing algorithms in the Blu-ray standard, and discovered that the algorithms serve two major purposes: they achieved as high a degree of compression as possible by converting the video signals into a seemingly random sequence of 0s and 1s; and they increased error tolerance by adding controlled redundancy into the data sequence, which also limited the number of consecutive 0s and 1s.
“These two purposes, the researchers said, have resulted in a quasi-random array of islands and pits (0s and 1s) with feature sizes between 150 and 525 nanometers. And this range, it turns out, works quite well for light-trapping applications over the entire solar spectrum,” the university said. “The overall broadband absorption enhancement of a Blu-ray patterned solar cell was measured to be 21.8 percent, the researchers report.”
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