From Switzerland a new process to make super photovoltaic solar panels: solar cells combining silicon and perovskite that have achieved record efficiency of 25.2%
Silicon-based PVs currently comprise the great majority of the photovoltaic solar cell market, thus including photovoltaic panels, having modern PV devices mainly constructed from silicon. Several the reasons: this material is affordable, stable and efficient. However, not so encouraging results have been reported in terms of efficiency and the idea of coupling it with other materials is now being taken in consideration.
A research team from the Federal Polytechnic School of Lausanne and the Swiss Electronics and Microtechnology Center have developed a new technique for producing solar cells in silicon and perovskite. The first results are very promising: they reported an efficiency of 25.2%, a record for a combination of this kind.
As a matter of fact, silicon photovoltaic panels, that are currently on the market, can only reach 20/22% efficiency: certainly a good value, although that has no longer much expectation of growth.
In the past few years solar energy research has witnessed the emergence of a remarkable new class of materials combining perovskite with silicon technology. This is a kind of tandem to create photovoltaic panels that is capable of absorbing more sun light and producing more electricity. In addition, it allows solar panels producers to obtain higher performance as compared to what silicon alone can achieve.
Obviously, this kind of panels costs much more. However, performance improvement should not affect the cost per watt and, over time, it could also, actually, lower it. Perovskites would thus become not only challengers but also enriching elements of silicon solar cells.
The perovskite-silicon combination
Pairing perovskite and silicon in a solar cell could help to combine the strengths of both materials.
Perovskite is better at converting green and blue light to electricity, while silicon specializes in red and infrared, so together they can capture a wider range of spectrum.
Practically, the combination of the two elements maximizes the use of the solar spectrum and increases the amount of energy generated, showing that 30% efficiency should soon be possible.
The main obstacles for these cells are in the production process. Normally, perovskite would be deposited on the surface like a liquid, but the structure of silicon makes it rather difficult.
Silicon is, in fact, made of a series of ‘pyramids’ about five microns high, a characteristic that allows light to be trapped and better absorbed. But this also means that liquid perovskite would not be able to cover the highest peaks.
Researchers prefer to be on the safe side and claim that it would not be the first time that a very promising technology during laboratory phase turns out to be difficult to industrialize and market.
In addition to the difficulties already mentioned and relating to the manufacturing process, perovskites have been found to be unstable at high temperatures and moisture sensitive. For a product that will have to be installed outdoor, on roofs or walls, this is a problem that needs to be immediately tackled.
What is perovskite ?
Perovskite was discovered in 1839 in the Ural Mountains but soon afterwards its existence was forgotten, as sometimes happens, since no one was able to think of its practical use.
As an opaque crystal of cubic form, it owes its name to Gustav Rose who named it in honor of the great mineral collector and Minister of the Russian Imperial Court Lev Perovskij.
Since 2006 there’s been a new interest in this mineral, a compound of calcium, titanium and oxygen, when Tsutomu Miyasaka, a researcher at Toin University (Japan), demonstrated the semiconductor characteristics of some perovskites, thus laying foundation to experiment with a new and promising type of solar cell.