Adding cesium to perovskite in solar cells boosts performance of silicon

Adding cesium to perovskite in solar cells boosts performance of silicon
Scanning electron microscope image of a cross-section of a planar heterojunction solar cell. PCBM, phenyl-C60-butyric acid methyl ester. Credit: Science (2016). DOI: 10.1126/science.aad5845

(Phys.org)—A team of researchers working at Oxford University has found a way to add cesium to perovskite solar cells to boost the performance of silicon, while maintaining the efficiency benefits it offers. In their paper published in the journal Science, the team describes their process which included finding a way to overcome the problem of efficiency loss in such materials that normally come about due to a limited range of solar spectrum use.

As researchers around the world continue to look for the next-generation material to use for solar power collection to increase , others continue to seek ways to improve the standard now in use: . In this new effort the research team noted the work done by others looking into the possibility of using perovskites (minerals made mostly of calcium titanate) as possible replacements for silicon, and found a way to add cesium to the mineral to make it work in tandem with silicon to create a solar collector that is up to 25 percent more efficient than those now in use. Such an improvement in performance could signal a transformation in real world use—solar power has thus far not proven to be efficient enough for the average consumer to cut the cord from the utility company—doubling efficiency might just make doing so a smart investment.

Up until now, efforts to get perovskites to work in tandem with silicon have been held back by inefficiencies in the due to the range of they were able to use—attempts to tweak the mix have led to instability in the materials. To overcome this problem, the team at Oxford came up with a process based on substituting certain ions in the material with cesium ions—it solved the spectrum problem, they report, while maintaining the stability of the overall structure.

The researchers acknowledge that their cells are not ready for prime time just yet, more work will have to be done to make sure the cells work in the real world, which could be a challenge, as perovskites historically have a tendency to decay when exposed to moisture and air.

Adding cesium to perovskite in solar cells boosts performance of silicon
Sketch of the tandem cell. Light is coming from below. Credit: Felix Lang/HZB

Explore further

Perovskites provide big boost to silicon solar cells

More information: D. P. McMeekin et al. A mixed-cation lead mixed-halide perovskite absorber for tandem solar cells, Science (2016). DOI: 10.1126/science.aad5845

Abstract
Metal halide perovskite photovoltaic cells could potentially boost the efficiency of commercial silicon photovoltaic modules from ∼20 toward 30% when used in tandem architectures. An optimum perovskite cell optical band gap of ~1.75 electron volts (eV) can be achieved by varying halide composition, but to date, such materials have had poor photostability and thermal stability. Here we present a highly crystalline and compositionally photostable material, [HC(NH2)2]0.83Cs0.17Pb(I0.6Br0.4)3, with an optical band gap of ~1.74 eV, and we fabricated perovskite cells that reached open-circuit voltages of 1.2 volts and power conversion efficiency of over 17% on small areas and 14.7% on 0.715 cm2 cells. By combining these perovskite cells with a 19%-efficient silicon cell, we demonstrated the feasibility of achieving >25%-efficient four-terminal tandem cells.

Journal information: Science

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Citation: Adding cesium to perovskite in solar cells boosts performance of silicon (2016, January 8) retrieved 22 August 2019 from https://phys.org/news/2016-01-adding-cesium-perovskite-solar-cells.html
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User comments

Jan 08, 2016
Lead? That's a nasty substance. Are they going to keep a registry of all these panels so that at end-of-life 30 years hence they can be properly disposed-of/recycled?

Jan 08, 2016
Lead? That's a nasty substance. Are they going to keep a registry of all these panels so that at end-of-life 30 years hence they can be properly disposed-of/recycled?

Do they keep a registry of all those wheel balancing weights they install so you can comfortably drive an automobile?

Jan 09, 2016

Do they keep a registry of all those wheel balancing weights they install so you can comfortably drive an automobile?


No, because the use of lead in wheel weights has been banned since 2005 in the EU, and most US states already ban them, and the EPA is considering a total ban. They use alloys of zinc and copper instead - a kind of soft brass also used in lead-free bullets - and steel weights glued or welded on. New wheels also come with internal balancing mechanisms.

The use of lead is being scaled back practically everywhere, because it is a huge environmental problem. The last bastions of spewing lead into the environment are pretty much small aviation (avgas) and gun ranges, and China.


Jan 09, 2016
Gun range lead contribution is TINY compared to coal burning. Doesn't even register. But ever think, if all the new technologies "gladly" reported on for increasing solar panel efficiency were actually REAL, a small number of solar panels would generate enough to power a city!! Most of it will never come to pass and peak efficiency has probably been 80% reached.

Jan 09, 2016
I'm not comfortable with how the term "efficiency" is applied to power generation from solar cells. I think that the mass of a power source should be factored into the calculation. Compare the mass of a hydro-electric turbine and the combined mass of the solar cells required to produce the same amount of energy. Do solar cells compare favorably?

Jan 09, 2016
I think it's great they continue to find ways to improve solar cells. If and when solar panels become competitive with carbon based electricity, that will be a great leap forward for our prosperity.

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