// Demonstrator for the CIGS perovskite tandem module

With the photovoltaic material of organohalide perovskites, semitransparent solar cells can be realised due to their high optical band gap of 1.6 eV, in which the maximum possible amount of light in the visible spectral range passes through the cell. This allows the production of thin-film tandem stacks with separately accessed contacts (“4-terminal”) using a semi-transparent perovskite cell and a CIGS solar cell mounted underneath. Together, they are able to more effectively exploit the solar spectrum and thus overcome the efficiency limit of a single cell.

In cooperation with the Interuniversity Microelectronics Center (IMEC) in Belgium and the Karlsruhe Institute of Technology (KIT), a scalable thin-film perovskite/CIGS photovoltaic module with an area of 3.76 cm2 and seven or four monolithically connected individual cells has been demonstrated. The efficiency of the individual CIGS module is initially 15.7% and is reduced to 5.8% if the semi-transparent perovskite module is mounted above it, now acting as an optical filter. However, since the upper perovskite module retains its efficiency of 12.0%, the overall calculated efficiency of 17.8% of the combined tandem stack is significantly higher than that of the individual modules. This clearly demonstrates the fundamental potential of this scalable thin-film tandem module technology. With further optimisations of the individual modules, in particular the efficiency and transparency of the perovskite modules, even higher efficiency increases will be possible in the future.


Dr. Erik Ahlswede
+49 (0)711 78 70-247
Semi-transparent perovskite module with seven sub-cells above a CIGS module with four sub-cells.
Structure of the tandem module consisting of perovskite (top) and the CIGS module (bottom).