Just three months ago, the ZSW (Center for Solar Energy and Hydrogen Research Baden-Württemberg) announced that its thin-film solar cells had already achieved a top performance of 22.0 % efficiency, a European record. The current improvement of an impressive 0.6 percentage points has now been achieved in a state-of-the-art laboratory coating facility using a co-evaporation process. The solar cells examined are based on the material copper indium gallium diselenide (CIGS). The higher efficiency results, among other things, from the optimization of the alkali post-treatment process of the CIGS surface. The Fraunhofer Institute for Solar Energy Systems (ISE) has already confirmed the results.

In the coming months, the ZSW intends to work together with its industrial partner Manz to transfer the new results from the laboratory to mass production. The Reutlingen-based engineering company Manz offers turnkey production lines for the manufacture of CIGS thin-film solar modules.

CIGS photovoltaics compared to silicon photovoltaics

According to the ZSW, progress in thin-film photovoltaics has accelerated significantly in just a few years: From 1998 to 2013, records were only broken every two to three years. Efficiency increased by an average of 0.1 percentage points per year. For almost three years now, the world records have been falling every six months. Growth rates are currently averaging 0.7 percentage points per year.

According to the ZSW, the latest research results could soon lead to serious competition with silicon photovoltaics, which has dominated the market for years. The lead over multicrystalline silicon cells is now 1.3 % . The ZSW scientists do not believe that the technological potential of CIGS solar cells has been exhausted with this new success. "I assume that we will be able to achieve up to 25 % efficiency in the next few years," says Prof. Dr. Michael Powalla, ZSW Board Member and Head of the Photovoltaics division.

Thin-film photovoltaics is also improving in other important key figures: CIGS PV is only slightly below multicrystalline silicon in terms of module efficiency, which is generally somewhat lower than that of smaller cells. The two technologies are close to each other with an efficiency of 15 to 17 %. The production costs of CIGS modules have now converged with silicon technology and are around 40 US cents per watt. In future, module efficiencies of 18% and more and costs of around 25 US cents per watt should be possible. In contrast to silicon PV, the low costs are already achieved with a relatively low production volume, according to the ZSW.