CD Laboratory for Applications of Sulfosalts in Energy Conversion

Research is being conducted into the use of sulfosalts as a new generation of semiconductor materials. The focus of interest is their application in photovoltaics, where they offer an efficient and favourable alternative to silicon.

Sulphosalts are a large family of minerals with outstanding semiconductor properties, but their use is currently still hampered by their often complex and very different structures. Comprehensive knowledge of their material behaviour is required for industrial use. It is precisely this knowledge that is being created for use in photovoltaics. All the steps required to produce efficient solar cells are taken into account.

One research focus is the production of different sulphosalts in flat layers, as required for solar cells. Thanks to their excellent suitability as semiconductors, even significantly smaller quantities of sulphosalts can achieve the same effectiveness as silicon. Thus, very thin layers of sulphosalts can already achieve high photovoltaic performance. Various processes for producing such thin films are being investigated, including ion atomisation and methods for growing single crystals. The semiconductor properties, thermodynamic behaviour and structural properties of the material are characterised and additionally optimised on the basis of layers produced in this way.

In a further step, solar cell structures are produced and their effectiveness tested. For this purpose, the thin layers of sulphosalts are applied to a glass substrate between a molybdenum back-contact layer and a zinc oxide top layer. The optimum combination and thickness of the sulphosalt layer would theoretically allow a conversion efficiency of 31.1 % of light energy into electrical energy. This would be significantly better than the maximum 25 % previously achieved by silicon-based solar cells. Irrespective of their effectiveness, solar cells made from sulphosalts could be significantly cheaper to produce than silicon-based solar cells.

In order to achieve precisely this goal and to assess competitiveness, the fundamentals of the properties and processing of sulphosalts are being researched here.