Production process

Sulfurcell develops and produces solar PV modules based on the absorber material Copper-Indium-Sulfide (CIS). Apart from the p-type absorber CIS – this is where the absorbed light is transformed into electric current – a module consists of a second, n-type semicondutor layer, a metallic back contact and a transparent, conducting front contact. Within a module a number of solar cells are series-interconnected.

The most common solar PV modules are based on crystalline silicon as absorbing material. CIS, the material Sulfurcell uses as absorber, has significantly better absorption properties. Therefore, the thickness of a CIS solar cell can be reduced to 1 % of the thickness of a common solar cell based on crystalline silicon.

The various layers a solar module consists of are deposited one after another on a glass substrate. The glass substrate serves twofold, as support for the very thin solar cells and as part of the later encapsulation. For the deposition of the various layers of a CIS based solar PV module techniques such as sputtering are used which have been applied successfully for a long time in the area of large scale glass pane deposition for architectal applications. Using sputtering large areas can be deposited homogenously at low energy consumption.

On the molybdenum back contact precursors consisting of copper and indium are deposited. In the presence of elemental sulfur vapor at a temperature of about 500°C the precursor reacts within a short time to form the absorber material CIS. The device is completed by the deposition of a front contact and after the contacting it is encapsulated to secure it from climatic influences.

In order to realize the integrated series interconnection of a number of cells on one substrate glass the deposited layers have to be disconnected at appropriate spots. This is done typically after the corresponding deposition process. Thus, the fabrication of the solar cells and the solar PV module is combined in one single process chain.