Energy

Two new solar cells break records, including highest efficiency ever

Two new solar cells break reco...
A small sample of the perovskite-CIGS tandem solar cell
A small sample of the perovskite-CIGS tandem solar cell
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A small sample of the perovskite-CIGS tandem solar cell
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A small sample of the perovskite-CIGS tandem solar cell
John Geisz (left) and Ryan France, researchers on the NREL study that broke the solar cell efficiency record
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John Geisz (left) and Ryan France, researchers on the NREL study that broke the solar cell efficiency record

Solar cells are constantly improving on the road to maximum efficiency. Now, three records have been broken by two different devices, including one that pushes the highest overall solar conversion efficiency towards the 50-percent mark.

The top honor was claimed by researchers at the National Renewable Energy Laboratory (NREL), who have developed a new solar cell with an efficiency of 47.1 percent. That makes it the most efficient solar cell of any kind in the world – for now, at least. These records have a tendency to be broken pretty regularly.

The device is what’s known as a six-junction III-V solar cell, meaning it’s made up of six different types of photoactive layer. Each of these is comprised of various III-V materials, named after their positions on the periodic table, which collect energy from different parts of the light spectrum. In total there are around 140 layers, packed into a solar cell that’s thinner than a human hair.

It’s also worth noting that the record was broken under light focused to be about 143 times stronger than natural sunlight. While the efficiency of this design is obviously going to drop in real-world uses, the team says that the device could be built with a mirror to focus the sunlight onto the cell.

The team also tested a variation of this cell under light equivalent to one Sun, and it still achieved an efficiency record of 39.2 percent.

John Geisz (left) and Ryan France, researchers on the NREL study that broke the solar cell efficiency record
John Geisz (left) and Ryan France, researchers on the NREL study that broke the solar cell efficiency record

In a separate study, researchers from Helmholtz Zentrum Berlin (HZB) broke a different efficiency record, this time for a new type of tandem solar cell.

Tandem solar cells are those with two different types of photoactive layers. In this case, one layer was made of perovskite, while the other was a combination of copper, indium, gallium and selenium, which the team calls CIGS.

The CIGS layer, which measures between 3 and 4 micrometers thick, is deposited first, then the perovskite layer, which measures just 0.5 micrometers thick, goes on over the top. The two work well together because the perovskite collects visible light, while the CIGS targets infrared. To improve the contact between the two layers, the team added a layer of rubidium atoms between them.

With this method, the team reached a peak efficiency of 24.16 percent. That’s not quite as high as silicon-perovskite tandem cells, but considering this is the first perovskite-CIGS tandem cell it’s a great start. The thickness, or rather, thinness, of the technology means flexible solar modules could be produced, which, being extremely light and stable against irradiation, would be well suited to applications in space.

A paper on the six-junction cell was published in the journal Nature Energy, while the perovskite-CIGS cell was discussed in Joule.

Sources: NREL, HZB

8 comments
JimFox
Likely cost? Efficiency is double that of current cells in production so here's hoping this can be scaled up & brought to market.
guzmanchinky
Someday if we reach 100%, I'll be curious as to how large of a panel we need (in Arizona somewhere) to power the US.
Expanded Viewpoint
Just as in real estate there are the first three rules of location, location and most importantly, location. in engineering there is cost, cost and the bottom line of cost v. efficiency. Of what good is it to have a device that is ten times more efficient, if it costs a thousand times more??
In building these new solar light conversion cells, what is the cost/benefit ratio? How expensive is the manufacturing process and what is the bill for the raw materials that are needed? What is the longevity factor? Too many times these very important details are left out of the equation, and businesses fail. Solyndra comes to mind here.
And WHY bother "juicing" the test parameters to get the numbers up, if those very same conditions are not going to be used in the actual applications? The real world is the real world, so let's not introduce any fake numbers in there, unless it's part of a stress test of some kind.
Joe
You can't easily assess cost until production economies of scale can fully kick in. Sure, right now im certain this cell costs far to much to justify producing, but now that it's demonstrated, researchers can evaluate how to incorporate various elements of it's structure with the knowledge of what can be expected.

I do like to focus on thinks that impact production in the nearer term, but that is not to say these proof of concepts are not important or that the boundaries of solar cells should not continue to be pushed - all or parts if it have the possibility of coming down to the mass market.
Kpar
Costs go down as knowledge and experience build up. Economies of scale will also be a huge factor. It won't replace fossil fuels for the forseeable future, but these technologies will do a GREAT DEAL to decentralize the power grid, and possibly avoid the collapse of civilization in the case of another "Carrington Event".
CAVUMark
Great work guys, but sorry - show me the money.
ljaques
3 keys in solar are reliability, longevity, and cost. I hope these hybrids quickly become all three.
martinwinlow
@guzmanchinky: The theoretical max efficiency of PV wafers under one sun (ie without mirrors etc) is 69% So, we'll never have a 100% efficient PV module. https://en.wikipedia.org/wiki/Solar_cell_efficiency.

As for the question of how big a PV array you would need to power the whole of the US, it's a square about 50 miles to a side using current commercially available modules. But then you'd have to store the energy for when it's needed. Cost? For the PV modules alone, about US$13 billion. For the rest of the installation another billion or so, but the storage is another matter.