The vast majority of commercial solar panels in use today rely on single-junction solar cells to absorb and convert sunlight into energy we can use to power our homes, cars, giant holiday decorations, and other gadgets. However, a physics theory known as the Shockley-Queisser limit states that a single-junction solar cell can only convert a maximum of 33.7% of incoming sunlight into energy. This theory has been broadly accepted as fact ever since it was first defined back in 1961. But now, scientists at the Institut de Ciències Fotòniques (ICFO) in Barcelona, Spain may have finally broken the efficiency ceiling.
A research team led by ICFO Professor Jordi Martorell discovered a way to make solar panel cells more efficient by limiting their photon emissions. Here’s why it works: After a cell absorbs sunlight, it then emits light back out in all directions. That process means it’s losing potential energy. The ICFO researchers converted the solar cell into a specially designed optical cavity that can still receive sunlight, but has less of an opening from which the energy can escape.
According to Dr. Francisco Bernal Texca, author of the team’s research article, their work may enable solar cells to reach efficiencies close to 43% (via ICFO). Bernal Texca further explains that “the simplicity of the cavity cell design does not introduce any additional fabrication complexity, unlike many of the approaches currently being explored to surpass the Shockley–Queisser limit.” This method is still experimental, though, so you’ll have to rely on other ways to make your home’s solar power more efficient in the meantime.
Widespread improvements to solar panel efficiency would solve many energy problems we currently face. But it’s still a long way from landing on our roofs. 
Despite recent solar panel innovations that have increased reliability, many of today’s solar panels achieve less than 25% efficiency, largely due to physical limitations alongside mass manufacturing material constraints, sun reflection, and potential shading. It’s difficult to reach the 33% ceiling dictated by the Shockley-Queisser limit, and it’s reasonable to assume that reaching the new theoretical maximum of 43% will be equally rare. It certainly doesn’t help that fossil fuels are ruining solar power by blocking out a portion of the sunlight, too.
But what if every solar panel actually could operate at 40% efficiency or higher? According to Prof. Martorell, “Achieving higher efficiencies is essential, because they directly translate into a lower cost per watt and more efficient use of land and materials for solar energy deployment.” That’s a modest way of describing an innovation that could potentially change the world. Another way to describe it would be to say that someday, consumer-grade solar panels may even be able to generate enough solar power for your home to go completely off-grid.

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