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Perovskite Solar Cell Record 23.9% Efficiency

perovskite breakthrough

Perovskite breakthrough may fast-track new solar PV technology

The Belgium IMEC research center developed a new Perovskite solar cell with a conversion efficiency of 23.9%.

According to IMEC this is even more than the conventional silicon solar cells.

This new step is promissing. Even without Perovskites, the cost of solar power is already competitive with fossil fuels in some markets.

If and when this new innovation breaks through commercially, costs will drop even further.

Benefits of Perovskite

Perovskite has a crystal structure that takes its name from a Russian researcher. Using perovskite as a semiconductor in PV modules has important advantages:

  • The raw materials required to produce this semiconductor perovskite are very cheap.
  • What’s more, you only need a very thin layer of perovskite in a solar cell, resulting in even lower material costs.
  • Perovskite can be applied with a relatively simple deposition process (the application of the layers on a given substrate), so that no expensive machines are required.
  • The perovskite layers can be deposited at low temperatures, which also keeps production costs low.

In principle, with the current state of perovskite solar cell technology, the same module efficiency can be achieved on glass or foil as currently with m-cSi, CdTe or CIGS. This, together with the fact that the manufacturing process can be very cheap, could result in a paradigm shift in the solar cell world.

Just like CIGS, Perovskite can be used on glass, but also on flexible foils, which can in turn be integrated into numerous products, such as automobile roofs or siding. If a transparent substrate is used such as glass or plastic, the perovskite-based solar cells could also be made semi-transparent, which could, for example, be used in window applications.

Transparency is also needed for the promising application of perovskite solar cells in so-called ‘tandem technology’. In combination with Si solar cells, efficiency could in principle end up exceeding 30%. (By comparison, the best c-Si solar cells can obtain an energy yield of 25.2% in the laboratory).

The US National Renewable Energy Laboratory is particularly enthused:

Work on solar cells using Perovskite material has advanced rapidly as a result of the materials excellent light absorption, charge-carrier mobilities, and lifetimes, resulting in high device efficiencies with significant opportunities to realize a low-cost, industry-scalable technology.

Perovskites challenges

Perovskites don’t like humidity, and so far researchers have been leaning on lead as a key component. Addressing those challenges while pumping up conversion efficiency and keeping manufacturing costs down is where it gets interesting. To overcome the challenges, IMEC modded a perovskite solar cell with silicon, a pathway that other researchers have also been pursuing.

Work on the new solar cell is part of IMEC’s ongoing partnership with the Netherlands/Belgium/Germany research hub Solliance, and it looks like all that brain power is paying off.

The partnership produced an earlier iteration of the new cell last year with a conversion efficiency of only 20.2%. And now, another 3.7% has been reached in just one year.

According to IMEC and Solliance, one key difference was switching up the type of perovskite used in the solar cell. The newer version uses the perovskite CsFAPbIBr (notice the Pb in there), which tuned the conversion efficiency of the perovskite layer to 15.3%. The research team also gave the architecture of the stacked perovskite-silicon combo a makeover. They texturized the topmost layer to reduce reflection, and they slipped a matching refractive liquid between the perovskite and the silicon.

More conversion efficiency

The IMEC research team has been keeping a close eye on manufacturing costs, and with that in mind, the new solar cell was designed with aperture areas of up to four square centimeters. That has a dampening effect on conversion efficiency — the researchers actually achieved 25.3% with smaller apertures — but the larger size is more consistent with current manufacturing processes.

Meanwhile, researchers at Columbia University have figured out why perovskite solar cells perform so well, even when they are defective (silicon is expensive partly because it has to be flawless to perform well).

The discovery could lead to new, more effective forms of Perovskite. That pathway also has the potential for developing new forms of perovskite that don’t incorporate lead. If all goes according to plan, it looks like the US Energy Department will reach its goal of sinking the cost of solar power down to the range of 2-3 cents per kilowatt hour by 2030.

Despite Trump’s pro-coal rhetoric Energy Secretary Perry has been given a free hand to promote his agency’s renewable energy mission, and he’s been doing that with bells on — at least, so far.

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