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Clean Power perovskite solar cell efficiency

Published on January 16th, 2015 | by Tina Casey


Solar Cell Efficiency Jumps 50% With Hand-Built Perovskite Layer

January 16th, 2015 by  

No matter how low the price of oil goes, evidence is growing that solar energy will keep giving fossil fuels a run for the money. That’s because solar cell efficiency keeps increasing, while the cost of materials keeps sinking, as illustrated by a new study just released by Stanford University. The research team was able to push up the efficiency of a low grade silicon solar cell by applying another relatively cheap material on top.

That would be the crystalline material perovskite, which is simple and inexpensive to synthesize. Just a couple of days ago we were remarking that a research team in South Korea has achieved a new perovskite solar cell efficiency that sets a new record, so let’s take a look and see what the Stanford team is up to.

perovskite solar cell efficiency

Cross-section of a tandem solar cell made with two photovoltaic materials, perovskite and copper indium gallium diselenide (Colin Bailie, Stanford University).

Solar Cell Efficiency And The Perovskite Problem

For those of you new to the topic, we’ve been all over perovskite lately. Though materials in the perovskite class aren’t particularly durable (they dissolve in water, for one thing), researchers have been attracted by their potential in a number of clean tech applications, including EV batteries as well as solar cells.

One thing that attracts researchers is the ability of perovskite solar cells to absorb only the visible part of the light spectrum. That has its pluses and minuses, but the big plus is that a perovskite solar cell can guarantee you the biggest bang per photon of visible light (that’s in comparison to silicon solar cells, which harvest energy from infrared light as well as visible light).


We’re not ready to ditch graphene as the nanomaterial of the new millennium yet, but perovskite is catching up fast. According to Stanford, perovskite solar cells were introduced just a few years ago, in 2009. The first attempts ranged close to 4 percent efficiency, and since then it’s vaulted up to 20 percent.

The challenge is to translate that labwork into something that can withstand real world weather conditions.

Maker’s Dream: A Hand Made Perovskite Solar Cell

The research team, co-headed up by grad student Colin Bailie, decided to tackle the problem in a way that would help keep driving the cost of solar energy down. That’s why the new perovskite solar cell is based on a conventional silicon cell. Here’s the strategy as described by Bailie:

Our goal is to leverage the silicon factories that already exist around the world. With tandem solar cells, you don’t need a billion-dollar capital expenditure to build a new factory. Instead, you can start with a silicon module and add a layer of perovskite at relatively low cost.

A huge obstacle in the team’s way was figuring out how to enable some photons to pass through the perovskite layer, so they could get to the silicon base. The solution was to place a transparent electrode on top of the cell, apparently making this the first ever two-electrode perovskite solar cell.

That gave rise to a new problem, which was how to figure out a way to get apply the electrode onto the perovskite solar cell without damaging it.

The answer to that was to do it by hand, using a technique similar to a temporary tattoo. The team took a sheet of plastic embedded with silver nanowires, and “rubbed” it onto the perovskite cell with the help of a pressure tool.

The result: the new perovskite layer boosted the efficiency of a low grade solar cell from 11.4 percent to 17 percent. That’s pretty good, considering that the perovskite cell alone only had an efficiency of 12.7 percent.

So, now what? Well, there’s still that pesky little problem of degradation in water to solve. Perovskite doesn’t hold up really well when exposed directly to light, either. So although the team is looking forward to achieving a perovskite tandem solar cell efficiency of up to 30 percent within the next ten years or so, it could be a while before we see that popping up in your friendly neighborhood solar garden.

Stay tuned.

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Note: If you’re wondering where the silicon is that the image above, the Stanford team also noodled around with solar cell efficiency using a cell made of copper indium diselenide (CIGS), so that’s what you’re seeing. The results for that are all right but not quite as impressive as the silicon version. Using the same 12.7 percent efficiency perovskite cell, they took a CIGS cell with a 17 percent efficiency and boosted the overall efficiency to 18.6 percent.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

  • Cg

    Maybe I missed the real story. If part of the solar spectrum is converted by the Perovskite for 12.7% and part by the spectrum is converted by polycrystalline silicon at 11.4% yielding a total of 24.1%, Where is the rest of the expected 30% supposed to come from?

    Of course, 12.7% + 18% for Single Crystal Silicon gives 30.7% ASSUMING that MORE of the solar spectrum is included in the the Single Crystalline/Perovskite sandwich. Maybe this is the >30% solution.

    Assuming a three layer, Polycrystalline/Singlecrystal/Perovskite could be made easily, the sum total *could be* (12.7 + 11.4 + 18)% = > 40% (or not?).

    The full story here would seem to need to address the full spectrum of solar sensitive layers… and… a quick primer on Perovskite solar cell spectral sensitivity versus Single and poly silicon spectral sensitivities to quickly see the overall sensitivity of a triple layer system for us ‘casual’ readers. Can we have >40%.. or not?

  • Ronald Brakels

    People keep talking as if oil is cheap. While it’s a lot cheaper than it was, I am so old I can remember when it was a lot cheaper in real terms than it currently is.
    Full Disclosure: I am twelve years old.

    • jeffhre

      In real terms. Well maybe the AUD has different real terms than the USD.

      • Ronald Brakels

        2003, 12 years ago, over 20% cheaper in real US dollars: http://www.eia.gov/forecasts/steo/realprices/
        This is not to downplay the recent price drop, it’s just that oil is still what people used to consider expensive not that long ago.

        • jeffhre

          I would take a guess, and say if you bracket that point in time, by going 12 months out in either direction, that you could find a point where oil was priced at 20% higher than now – in real terms.

          • Ronald Brakels

            No. If you look at oil prices at the link I gave you will see that they weren’t higher than today’s price in real terms for over 11 years and if you go back before that you’ll see that it doesn’t get more expensive than today until 1985. So oil seems expensive to 12 year olds and to those who have managed to live to the ripe old age of 29.

          • jeffhre

            I’m 12.

  • Adam Devereaux

    What’s interesting is this from a add-on product market- this is whats great about the solar market being the size that it is. It would be worth it for someone like 3M to invest in developing a product offering for existing silicon manufacturers to add to their products to boost efficiency. If you could get a straight 20-50% efficiency boost on your existing product line and the additive was cost effective then this may come to exist.

    It’s the fact that the solar market is large enough that big universities and companies would consider investing in the product development that excites me.

  • JamesWimberley

    Tina: “the team is looking forward to achieving a perovskite tandem solar cell efficiency of up to 30 percent within the next ten years or so.”

    They boosted a cheap 11.4% solar cell to 17%. If Stanford were less hard-up, its graduate students could go out and buy mono silicon cells over the counter at over 20% efficiency. With these, they should be at 25% already with the tandem. I safely predict lab tandem cells at 30% in the next two years, not 10. The real challenge for commercialising them is the stability and durability of the perovskite layer.

    • Omega Centauri

      Both of these could be important issues, i.e. getting a decent boost on top of an already good cell, and the durability of the provskite layer. Don’t hold your breath waiting for a big efficiency boost in economically viable products.

      • JamesWimberley

        You may have missed the announcements by JA Solar and Trina of 20% efficient polycrystalline silicon cells, very close to production.

  • MarTams

    This is good development. I hope that they will ultimately attain the 30% efficiency in less than 5 years and still keep the price per Watt down. Higher efficiency cells win all the time if it has the same price per Watt.

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