Blu-ray discs are good for the subset of the population that still isn't down with streaming (or still watches things on screens that are larger than my laptop's)—but it turns out they might play another, more environmentally important role in the future: The surface of a Blu-ray disc also happens to be the perfect thing to make highly efficient solar cells out of.
In order to encode so much data on a disc that's the size of your standard CD, Blu-ray engineers had to develop highly complex, highly compressed patterns to actually hold the data. That pattern, made up of a series of extremely tiny raised and lowered portions, called "pits and islands," turns out to be extremely useful for capturing light when used on a solar cell. That's because those pits and islands create more surface area than your standard solar cell, making more space for the cell to absorb light.
In a paper published today in Nature Communications, Jiaxing Huang of Northwestern University explains how Blu-ray engineers had already done the heavy lifting that solar energy engineers have been trying to crack for years.
"It was something that one of my coauthors was already trying to do—fabricate these quasi-random patterns," Huang told me. "But, first, it's not easy to design a random pattern in the first place, and then, these patterns can't be created on solar cells using cheap techniques. We were talking about it and realized that Blu-ray patterns are already optimized for what we wanted to do—the work's already been done for us."
In trying to cram so much data on a disc, those engineers had to create coding algorithms that automatically turned video and audio signals into random sequences of binary 1s and 0s.
Meanwhile, error tolerance coding techniques—which make it so the Blu-ray player computing processor doesn't overtax itself—set lower and upper limits for those sequences of binary, making it truly "quasi" random, Huang explained. He says that quasi-randomness is key for what his team was trying to do.
"We just removed the coating and, once you do that, you expose the pits and islands. We could actually just use those directly, but it's kind of difficult," Huang said. "So, instead, we replicated it on a rubber stamp and push it onto the solar cell structure."
In test results, the Blu-ray-optimized discs were, on average, about 10 percent more efficient than existing solar cells. In the real world, it's hard to say how much better they'd be, but
Huang says that they certainly show better light absorption and efficiency than what currently exists on the market. He says there's potential for this on the commercial market, and it's much easier to create solar cells with Blu-ray patterns than to develop a novel pattern yourself.
So, I'm sure you're wondering what movie he encoded onto his solar cells. Turns out, it doesn't matter—they're all more or less equally superior to what exists. But, for the record, it was Supercop, starring Jackie Chan.