How to turn Blu-ray discs into better solar cells

As it turns out, old Blu-ray movie discs can be turned into something other than just colorful drink coasters: their semi-reflective surfaces may be the key to making more efficient solar cells. This discovery was made by engineers from Northwestern University and published in the journal Nature.

 

Engineers already know that solar cells are more efficient at trapping light if they have non-smooth or “quasi-random patterned” surfaces,  the kind that give Blu-ray discs and butterfly wings their distinctively shiny appearance. 

 

However, the very high cost of manufacturing these patterns on solar cells' active layer doesn't make them appealing for mass production. And that's where Blu-ray discs come in.

 

Although they may look smooth, Blu-ray discs are etched with nanostructures—the islands and pits that store the information contained in high-definition movies. These nanostructures are also what make Blu-ray discs shiny and colorful in the light. This ability to trap light made them potential test subjects for imprinting solar cells.

 

"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," said Jiaxing Huang, one of the study's coauthors. "It's as if electrical engineers and computer scientists developing the Blu-ray technology have been subconsciously doing our jobs, too."

 

The NU team removed the lamination from a copy of Jackie Chan's "Police Story 3: Supercop" and poured polydimethylsiloxane (PDMS) plastic over it to create a negative mold of the disc's nanostructures. They then used the mold to stamp the nanostructure patterns onto a prefabricated polymer active layer.

 

When comparing the results for the Blu-ray imprinted solar cell to a non-patterned solar cell, the Blu-ray imprinted cell showed a 21.8% increase in light absorption over the entire solar spectrum, leading to an 11.9% increase in power conversion efficiency. The team then used various Blu-ray discs with comparable results, leading them to conclude that it didn't matter what movie was on the disc.

 

The engineers suggest that the Blu-ray patterns could also be used to improve the light trapping in other types of solar cells, not just polymer cells.

 

"It has been quite unexpected and truly thrilling to see new science coming out of the intersection of information theory, nanophotonics and materials science," Huang said. — TJD, GMA News
 

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Macy Añonuevo earned her MS Marine Science degree from the University of the Philippines. She is a published science and travel writer and was a finalist in the 2013 World Responsible Tourism Awards under the Best Photography for Responsible Tourism category. Her writings and photographs may be found at www.theislandergirl.com.