Researchers at the Karlsruhe Institute of Technology (KIT) in Germany have developed a laminated solar cell based on chalcogenide as well as copper/indium/selenium (CIS) thin films.
The cell is described as the first photovoltaic cell of its kind to achieve an efficiency close to 25 per cent. The new photovoltaic cell has a qualified efficiency of 23.5% and a maximum efficiency of 24.9%.
The efficiency has been verified by the Fraunhofer ISE (Fraunhofer Institute for Solar Energy Systems).
The scientists used CIS with a band gap of approximately 1.03 eV and a small amount of gallium, as well as tri-cationic chalcogenide with a band gap of approximately 1.59 eV, using an anti-reflective coating (ARC) to enhance the coupling light and increase the general photocurrent. The cell has a power conversion efficiency of 24.9%, an open circuit voltage of 1.57 V, a short circuit current of 21.1 mA and a fill variance of 75.2%. The top and bottom cells have a doped photocurrent of 20.4 mA and 20.7 mA respectively.
In September 2020, the new Calcium Titanite CIGS stacked cell from the National Renewable Energy Laboratory achieved a world record efficiency of 24.16%, which was officially certified by the CalLab laboratory of the Fraunhofer Institute for Solar Energy Systems (ISE).
The stacked cells combine two different semiconductors which convert different parts of the spectrum into electrical energy.
Photovoltaic cells consisting of copper, indium, gallium and selenium can be deposited as thin films with a total thickness of just 3-4 microns. The chalcogenide layer is even thinner, at just 0.5 microns. Thus, new laminated solar cells made from CIGS and chalcogenide are well below 5 microns thick and can be used to produce flexible solar modules.