Perovskite-based solar panels are the most promising bet in the search for a replacement for current crystalline silicon panels. Not only do they take advantage of a wider range of the solar spectrum, but they are also cheaper and have a property that makes them special: a certain flexibility that allows them to adapt to curved surfaces.

The big problem with these panels is that, since they have been in development for less time than crystalline silicon panels, their stability, durability and effectiveness are less. We have been correcting this over time, and a last big step has been taken by a team of researchers from the German University of Potsdam together with colleagues from the Chinese Academy of Sciences:

An efficiency record for a perovskite solar cell.

Record breaking tandem solar cell

The solar industry has its eye on perovskite cells. Apart from the advantages mentioned, they are also more flexible than silicon, they have high efficiency in thin layers, which reduces the use of material necessary in their construction and their construction is more respectful of the environment as it does not require ovens. powerful in its manufacture.

However, it has a series of drawbacks such as lower stability as it degrades more quickly, significantly reducing its useful life, and a lead content that is not found in crystalline silicon (and, therefore, raising ecological concerns).

A multitude of laboratories and centers around the world are investigating how to solve these problems to guarantee their mass commercial viability in a market in which crystalline silicon products are more than established, with prices at rock bottom thanks to giants like China.

In recent years, we have seen silicon-perovskite tandem mixtures with efficiencies of up to 40%, but the challenge is to completely eliminate silicon from the equation. In China, panels without a single bit of silicon have already been created with high sunlight conversion efficiency, and the latest is a tandem solar cell based only on organic components.

The result of a collaboration between the University of Potsdam and the Chinese Academy of Sciences, the new cell has a conversion record of 25.7% for a cell based on a broadband perovskite bottom cell and a narrowband organic top device.

Thus, this ‘sandwich’ is composed of a layer of transparent conductive oxide, a perovskite absorber with a bandgap of 1.88 electrovolts, a new passivation layer based on 1,4-diammonium cyclohexane (CyDAI2), a organic absorber with a bandgap of 1.27 eV, a PDINN cathode layer and a silver electrode.

This concept was presented in a study of Nature and what stands out, such as we read in PV-Magazine, is that it has great absorption of the red/infrared range. According to the researchers, “the tandem solar cells were limited by the perovskite layer, which presents strong efficiency losses if it is tuned to absorb only the blue/green parts of the solar spectrum. To address this problem, we used a novel applied passivation layer to perovskite that reduces material defects and improves the performance of the entire cell”

That CyDAI2 passivator is one of the keys to reducing circuit voltage mismatch and, tested under standard lighting conditions, the tandem cell achieved an energy conversion of 26.4%, with a certified efficiency of the aforementioned 25.7%. . Those responsible for it claim that it is the current world record for this type of cells and something very interesting is the absence of lead.

It may seem like a small efficiency and, obviously, lower than the perovskite and silicon tandems, but as we said, it is a new technology, much less consolidated than the current crystalline silicon cells and which still has a long way to go. The good thing is that steps forward are being taken almost every week and 2024 has been a good year for this technology.

Not only are perovskite solar panels already being marketed (on silicon, yes), but China has just covered a mountain with this type of technology. The bad news for perovskites? That silicon ones continue to evolve.

Images | University of Potsdam

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