The use of solar photovoltaic cells as a renewable energy source is booming, as the technology becomes more efficient and less expensive. Stacking perovskite solar cells on top of silicon ones is one way to increase the amount of sunlight harnessed, and now researchers at Australian National University (ANU) have broken a new efficiency record for these tandem solar cells.

The researchers say that their new perovskite-silicon tandem solar cells have hit 27.7 percent efficiency for converting sunlight into energy. That’s more than double where the technology was just five years ago (13.7 percent), and a decent step up from reports two years ago of 25.2 percent.

Interestingly, this is already outperforming most commercially available solar cells, which hover around the 20-percent efficiency mark. These are based solely on silicon, and that technology is expected to bump up against its maximum upper limit in the next few years.

Both silicon and perovskite are good at converting sunlight into energy, but together they work even better. That’s because the two materials absorb different wavelengths of light – silicon harvests mostly red and infrared light, while perovskite specializes in green and blue.