“My dream is to have solar cells that after some time will degrade like leaves on a tree”

Materials called perovskites will transform the way we build and use solar cells – by making them bendy, says the researcher behind the idea

What’s the special ingredient in the solar cells you’re designing?

Perovskites are a large family of materials with a common crystalline structure, and include natural minerals or films synthesised in the lab. Today most solar cells are made of silicon, which has to be at least 80 micrometres thick – about the width of a human hair – to convert as much light energy as possible into electricity. Perovskite cells can be just tenths of a micrometre thick, making them ultra-lightweight and very cheap, while still keeping the efficiency of bulkier silicon cells.

What can they do that silicon cells can’t?

Our vision for them hinges on the fact that they can be flexible because they’re so thin. They can be printed or sprayed on foils, and because the cells are only 0.2 micrometres thick, they’d be light as air. And they can be semi-transparent or coloured, so you could put them in windows, or have a building that from a distance you don’t see is covered with solar cells but that could produce enough electricity to power itself.

The best silicon cells convert about a quarter of the solar energy falling on them into electricity. Are perovskite cells as good?

The theoretical limit for perovskite cells is about 30 per cent, so at least 28 per cent should be possible. They are already at 18.4 per cent. You don’t need complicated equipment to produce these and the materials aren’t expensive. So now, everybody’s started to work on perovskites and progress is much faster.


So could perovskite replace silicon?

Silicon lasts 25 or 30 years; so far perovskites have only reached 1000 hours. Fighting silicon would be suicide, and you’d lose before you even start because of the lifetime.

Trees get energy from leaves with only about 3 per cent efficiency, but they have a lot of leaves and they are very “cheap” to produce. Every year they are exchanged for new ones. My dream is to have solar cells that after some time will degrade like leaves on a tree. Perovskites are partially organic, so it should be possible. If we can get rid of the small amount of lead they contain, it would be easier to make them safely disposable. Then you could use the cell for for power when you’re camping, for instance, and throw it away after.

Are you at all worried that the potential of perovskites might be overhyped?

Perovskites have already proved that they work, so I don’t think this will implode. I really think we can improve them, and even if we can’t they are already good enough to use where you can’t use silicon. When I look around, I imagine covering everything with perovskites.

Could your work help unearth other promising materials?

The particular perovskite we’re using now is one IBM was testing for transistors and other applications 20 years ago. The only thing they didn’t try was solar cells. If they had, we might be living in a completely different world. I think there might be a lot more materials like that out there.

Profile Olga Malinkiewicz is co-founder of Saule Technologies, a solar-cell start-up in Warsaw, Poland. She invented a way to create the cells on ultra-thin foils using novel materials, an approach her company is now trying to commercialise

This article appeared in print under the headline “Solar’s foldable future”