Messer GmbH, one of the few remaining family-run industrial gas giants, is investing efforts into thin-film solar cells that are both environmentally friendly and versatile. In a recent corporate statement the firm highlighted the importance of industrial gas to this burgeoning arc of environmentally friendly power.

Compared with conventional solar cells, consisting of silicon crystals, the eco-alternative only requires a fraction of raw material and is purported as much more flexible to use. Budapest’s, GreenSolar Equipment Manufacturing Ltd., develops and produces what are called tandem thin-film cells; their silicon layers are only a few micrometers thick because they are formed from gaseous precursors. But as Messer emphasised, other industrial gases are also important.

However, without a doubt, the most important ingredient is silicon, nevertheless as Messer explained, its use is associated with problematic CO2 emissions. “The production of pure silicon requires large amounts of energy and is associated with considerable CO2 emissions. The crystalline form also places considerable restrictions on the possibilities of processing and forming. That is why there is growing interest in types of silicon that are suitable for photovoltaics but require the use of much less material while at the same time being easier to process.”

Wafer-thin silicon
According to Messer, these requirements as best met by amorphous and microcrystalline silicon, the firm explained, “Since they are only required in extremely fine layers of just a few thousandths of a millimetre, silicon consumption per square metre of solar cell can be reduced by up to 99.9%. GreenSolar uses the so-called tandem process, whereby layers of amorphous and microcrystalline silicon are formed on top of each other. The two materials have different properties; in combination they form a cost-effective solar cell with a relatively high degree of efficiency.”

And this is where industrial gases take to the stage. In order to produce the thinnest possible layers, photovoltaic materials are vapor-deposited onto a base layer. To begin with, therefore, they have to be supplied in gaseous form and fixed to the base in a sophisticated process. This involves the use of silane – a compound of silicon and hydrogen (SiH4) – as well as gaseous compounds of boron and phosphorus.

Messer went on to point out the involvement of argon, helium, methane, nitrogen and hydrogen. Indeed, Messer works closely with GreenSolar and even jointly developed complete gas supply systems, specifically tailored to the tandem process. Furthermore, the gas supply chain is also environmentally friendly and tailored to minimise CO2 emissions.

The German industrial gas firm explained, “The gas cylinders are stored in a safety cabinet. From there the gases are first moved to a mixer, where the specifically tailored gas mixture is prepared. It is then piped to the panel production area. Thanks to the huge saving of material, a lot less energy is used during semiconductor production, and carbon dioxide emissions are also reduced significantly. The thin-film cells are therefore particularly environmentally friendly, both in terms of their production and, subsequently, as a non-polluting power supply.”