Perovskite: Miracle material for solar cells

DW (English)

Perovskite is much more efficient than standard silicon solar cells. Its crystals are easy to synthesize and don't have to be mined like silicon. Perovskite could revolutionize solar technology.

Transcript

00:00This tiny solar cell might be about to revolutionize solar energy as we know it.

00:05It's way more efficient than your standard silicon solar cell.

00:08It can be easily synthesized and doesn't need to be mined like silicon.

00:12And it can work on thin film to power your smart home speaker, but it also can go on your roof.

00:18Say hi to this crystal structure called perovskite.

00:22It promises improvements to solar cells that are almost too good to be true.

00:28To understand why they are so superior to your standard silicon cell,

00:33I went here, the Helmholtz Institute in Berlin.

00:36They've been researching perovskites as a sun-absorbing material for more than a decade.

00:45And this is the guy in charge of the research,

00:47Steve Albrecht. He even set world records for the most efficient perovskite solar cells.

00:53So on a very basic level, what does perovskite look like?

00:58The term perovskite is a very generic term for a specific crystal structure, right?

01:04You can see that here, over there.

01:06So the crystal structure has the ABX3 formula,

01:10and like each component is a certain either element or molecule.

01:15One of the most common combinations in this structure is methyl ammonium as the A on the

01:20corners, the metal lead for B in the center, and chloride or iodide as the X,

01:27which form around the metal.

01:28But there is a vast range of materials that can be used and combined,

01:33and it's quite wild how easily these can be put together.

01:38Oh, this is a lab environment.

01:40But before we do that, security first,

01:42as we are going to work with toxic lead with one of Steve Albrecht's colleagues.

01:46Okay, looks good. I think you're good to go.

01:49You look a bit like a veterinary.

01:53Okay, time to get in our base materials.

01:56Matthew mixes methyl ammonium chloride and

01:59lead iodide to later create our ABX3 crystal structure.

02:05So what is now the advantage of these materials compared to silicon?

02:10So I believe that one of the main advantages of perovskite over silicon

02:15as a material is the ease of processing.

02:17So silicon is something that is relatively energy intensive to fabricate,

02:22but this is something that can be done at close to room temperature,

02:26so it doesn't require much energy, so it's easy to do.

02:29Everything is relatively abundant, and so it shouldn't be a bottleneck for production.

02:37Now that we have the base materials, we need to produce sun-absorbing perovskite out of it.

02:42Matthew does this by using a technique called spin coating.

02:46But perovskite solar cells can also be directly printed onto surfaces

02:51using similar processes to those needed for printing newspapers.

02:57Spin coating, however, can be tedious.

03:04Matthew accidentally dropped the glass.

03:06Not a big problem in a lab environment, but for commercial production, this is not viable.

03:11Matthew gives it a second try, and this time everything works.

03:15After the spin coating, it goes onto a heating plate,

03:18and the darkening shows us that the crystals are being formed.

03:22It works the same way as when salt water evaporates and you start to see the salt.

03:28There are cells like this one here which are only made out of perovskite,

03:32but in many cases there is a silicon layer beneath them.

03:36These cells are called tandem cells and look like this.

03:39Right now they are the most promising candidates

03:41when it comes to increasing the efficiency of solar cells.

03:45But at some point it might be also possible to abandon the silicon completely.

03:50To test their tandem cells efficiency,

03:52the researchers at Helmholtz Institute use a sun simulator.

03:55It determines exactly how much sunlight is converted into electricity.

04:00What kind of efficiency did we just measure?

04:03So here we measured almost 30 percent, a quite nice achievement.

04:07Why does a tandem solar cell reach that much more efficiency than single junction solar cells?

04:13So tandem solar cells make much more use of the incoming light.

04:18So we have our solar spectrum.

04:21The solar cells, they share the spectrum kind of.

04:24The perovskite solar cell in this case makes use of the visible wavelength.

04:30So everything which we can see by eye

04:32is then converted in the perovskite solar cell into electrical energy,

04:36whereas the infrared light passes through the perovskite cell

04:41and is then converted in the silicon solar cell,

04:43which is quite efficient in converting infrared light.

04:47So they share the spectrum and each cell is very efficient in their region.

04:52It doesn't sound like that much,

04:54but Eike tells me that this way roughly 50 percent more sunlight

04:57can be converted into electrical energy.

05:01So more overall sunlight can be absorbed,

05:03but you can't buy any of these tandem solar cells yet,

05:07because before they go into serial production,

05:09there's a lot of stuff that needs to be fixed.

05:12A major issue is the stability of the perovskite structures used in tandem solar cells.

05:17Perovskite structures are easily put together at low temperatures as we saw earlier,

05:21but they also come apart easily.

05:24Even the charges that travel through the perovskite in the solar cell

05:27can create defects and destroy the perovskite structures.

05:31Also, external factors like moisture, heat, oxygen and UV light

05:37can break it down further and quickly decrease its record-breaking efficiency.

05:42This whole process is called degradation,

05:44which researchers and companies are trying to fight with different forms of encapsulation.

05:49It seals off the solar modules from external influences

05:52and is an essential step for commercialization.

05:57Q-Cells, which is part of a European academia and industry partnership,

06:01plans to develop commercial-sized modules

06:04with an efficiency of 26% over a lifetime of 30 years.

06:10Oxford PV, a company founded by Oxford University graduates,

06:14has reached an efficiency of 28.6% and supposedly solved the degradation issue already.

06:21But neither company has published verifiable data yet.

06:25Nor is there a lot of published research on real-world outdoor tests.

06:31These are a lot of solar cells that you test here.

06:34Wow!

06:35This is Caroline Ulbricht.

06:37She oversees the degradation tests of tandem solar cells at the Helmholtz Institute.

06:42At what kind of stabilities are we currently looking at here?

06:46Sometimes they fail after a few days, but sometimes they last for years.

06:50Ulbricht's team measured a loss of 20% in efficiency in just half a year.

06:55It takes silicon solar cells roughly 20 years to reach that level of degradation.

07:00Some companies say they've already fixed this issue and are ready to go to market next year.

07:07Do you believe that's possible?

07:09We do sometimes hear rumors also at conferences,

07:12but they normally don't show the data.

07:14It's all very secret.

07:16Tandem solar cells would also need to price-match existing cells,

07:20a task that experts view as difficult to achieve,

07:23as costs for electricity from solar have declined by 89% since 2016.

07:30It's now more expensive to install silicon solar panels than to produce them.

07:36Solar tandem cells have a great potential,

07:38but there are still a lot of things that need to fall into place for them to work.

07:42And I'm really, really curious if they're actually going to be on the market next year already.

Category

Transcript

Recommended