European countries have increasingly invested in renewable energies in recent years, with photovoltaics playing a decisive role here. Germany, Spain, Italy and France have considerable capacities and there is an increasing demand for photovoltaic systems.

The big problem with photovoltaics is efficiency, especially in the context of silicon solar cells. Efficiency refers to the ability of solar cells to convert sunlight into electrical energy and how effectively this process occurs. Silicon is currently the most widely used material for solar cells due to its semiconductor properties and availability.

Wafers for solar cells today are mainly made of monocrystalline silicon.
The cheaper polycrystalline solar modules are almost only installed on large roofs. In the case of multicrystalline modules, plant operators must be content with a maximum efficiency of 18 %. For thin-film modules, the maximum efficiency is even 16 % and below.

In general, only relatively small amounts of the solar radiation that occurs can be converted into electrical energy. Research teams around the world are constantly working to improve the efficiency of solar cells and modules. However, the potential of silicon photovoltaics is practically exhausted with a maximum of 25 % efficiency – even the theoretically maximum possible efficiency is only 29 % due to the material.

From high-performance solar cells with gallium and indium compounds, 45 % could already be achieved over short periods in the experimental stage. However, practical use is still a long way off due to the costs involved.

The solution

The use of so-called “single-walled carbon nanotubes” (SWCNT) for solar cells is ideal. The reticular width of the CNTs exactly matches the sunlight spectrum in the infrared and ultraviolet range, bringing extremely high carrier mobility and reduced carrier transport scattering. Based on theoretical calculations, solar cells based on CNT achieve an efficiency of 60 % and more.

Graphene has even more properties that go beyond this and is also already being used in research. Graphene is transparent and graphene-based solar cells have a light transmission of over 90 %.

The problem of efficiency-reducing factors, the angle of irradiation and the heating of the silicon collectors will also be a thing of the past.

The use of CNTs and graphene not only enormously increases the efficiency of the solar cells and thus produces significantly more electricity per unit area, but also drastically reduces the amount of material required. Ultralight solar cells can thus pave the way for completely new applications.

The fact that graphene and CNTs are not yet used in practice in photovoltaics is due to both their availability and the fact that their costs are still too high.

AGT was able to solve both problem areas through innovations in the manufacturing process of these high-tech materials. An important step for the realization of the desired energy turnaround.


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