One stop PV thin film coating moves one step closer

Thin film solar cells are considered by many to have great potential in that they can be applied to surfaces where standard photovoltaic modules cannot. However, slow and labor intensive manufacture of thin film modules has hampered rapid development in the field. A research institute in Stuttgart, Germany, has announced findings that may solve these problems making the manufacture of thin film photovoltaic more efficient.

Late last month, the Center for Solar Energy and Hydrogen Research in the German state of Baden Württemberg (ZSW) announced a breakthrough with the potential to improve the thin film manufacturing process. The ZSW laboratory experiments have resulted in a method for, "efficient web coating of thin film solar modules made of copper indium gallium diselenide (CIGS) on plastic film." At the same time, the solar cells maintain efficiency of 10.2 percent. ZSW claimed this has the potential to, "create a new generation of affordable, flexible photovoltaic modules."

The ZSW researchers previously had developed a technique whereby all the production steps were completed in one continuously running system. But this new development is that CIG application processes can be completed at the same time. In a statement to pv magazine the ZSW researchers elaborated, "the most important step is to complete all deposition processes in parallel. This means that we will first integrate a vacuum-deposited buffer layer and match the deposition speed of all coating processes."

The CIGS coating process used by the research team is cathode sputtering but, clarified ZSW’s Michael Powalla, "the co-evaporation of the CIGS absorber and the deposition of the transparent front contact layer are located elsewhere in the system." In short, while the ZSW research may have reduced the CIGS deposition process to one stage, CIG thin film manufacture remains a multi-stage process.

The researchers also noted that as the process is carried out in a vacuum chamber, "the interfaces will not be contaminated by oxygen or atmospheric moisture." Although whether this is advantageous to the production process is not clear.

The timeframe for commercial application of this technology is also unclear, however the Stuttgart team anticipates that it may take between five and ten years. "New developments within other institutes and companies," ZSW told pv magazine, "may compliment research and speed up commercial delivery."

pv magazine has requested more details as to the sputtering process the ZSW researchers used and the target used in the one stop process.