Blu-Ray discs can be used to manufacture more efficient solar cells. The same process that forms the unusual colors of the discs is also capable of capturing light to generate green energy, new research reveals.

The unusual colors seen in Blu-Ray discs are formed from a process called structural color. Rather than frequencies of light being selectively reflected off a surface, microscopic, translucent shapes affect photons to create color.

Solar cells, like Blu-Ray discs, must capture light. Networks of microscopic ridges carved into solar devices have been shown to raise the efficiency of the panels at capturing sunlight that falls upon their surface. However, these patterns are often difficult to create, and expensive, making real-world applications impractical.

Patterns like those in Blu-Ray discs are sometimes found in nature, such as the wings of some species of butterflies.

Northwestern University researchers wanted to test if Blu-Ray video discs could be utilized as a low-cost alternative to the expensive custom-designed patterned solar cells. The team used scissors to trim around the edges of a Blu-Ray disc. They opened the disc, and poured melted plastic onto the etched surface, and allowed the polymer to dry overnight. Researchers manufactured their own solar cells, and stamped some of the devices with their plastic mold, leaving others smooth to serve as a control in the experiment.

Quasi-random patterns, those balanced between complete order and chaos, are the most efficient at collecting desired wavelengths of light. If surfaces are too random, they cannot direct specific wavelengths of light, while those patterns which are too structured can only direct photons of a specific frequency.

"The big surprise is that the pattern worked so well," Jiaxing Huang, a materials scientist at Northwestern University, said.

Blu-Ray video discs were introduced by Sony in prototype form in the year 2000, designed as a replacement for the DVD format. They are capable of holding far more information than the earlier home entertainment technology.

"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 said.

Investigators measured improvement in the solar collection at a significant 21.8 percent.

The Blu-Ray disc used in the first experiment was a copy of Police Story 3: Super Cop, staring Jackie Chan. Further investigation, using different movies and television shows, including some shot in black and white, showed no difference in performance from the Chan comedy.

Use of Blu-Ray discs as a template for solar cells was detailed in the journal Nature Communications

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