Silicon has long been the gold standard for solar cells, but it’s beginning to reach its limit. Perovskite is emerging as a promising partner, and now engineers have achieved a new efficiency record closing in on 30 percent for this kind of tandem solar cell.
Ever since perovskite burst onto the solar cell scene around a decade ago, it’s broken efficiency records at a blistering pace – especially when it’s paired with silicon. Just five years ago, tandem solar cells had a maximum efficiency of 13.7 percent, two years ago it was up to 25.2 percent, and earlier this year the tech hit 27.7 percent.
Now, a team led by scientists at Helmholtz-Zentrum Berlin (HZB) have managed to squeeze an impressive 29.15 percent efficiency out of their tandem silicon-perovskite solar cell. That’s approaching the milestone 30 percent mark, and not too far off the theoretical limit of 35 percent.
For reference, the efficiency of either silicon or perovskite alone usually maxes out at around 20 percent. They play well together because they absorb different wavelengths of light – silicon focuses mostly on the red and infrared part of the spectrum, while perovskite excels at green and blue light.
To make the new device, the team started with a perovskite composition with a 1.68-eV band gap. Then they developed a new substrate made of carbazole-based molecules with methyl group substitution, which helped electrons flow through to the electrode more efficiently.
In its current form, the solar cell was tested in a 1 cm2 (0.2 in2) sample, but the researchers say that it should be relatively simple to scale up to more practical sizes.
Earlier this year this efficiency record was certified at Fraunhofer ISE and listed in the NREL chart, which has kept track of solar cell technology progress since 1976. Now, a study describing the new work has been published in the journal Science.
Source: Helmholtz-Zentrum Berlin via Eurekalert