Oxford PV, a spin-out of Oxford University, is producing the perovskite-silicon solar cells in M6 format with an efficiency of 26.8 percent in small series at its factory in Brandenburg, Germany. “This new world record is a crucial milestone for Oxford PV, proving that our tandem solar cells can deliver record-breaking performance when assembled into solar panels,” says David Ward, Chief Executive Officer, Oxford PV.

Commercial production of the tandem solar cells will begin this year. Perovskite silicon tandem cells have a theoretical maximum efficiency of over 43 percent compared to less than 30 percent for silicon solar cells.

Using the Oxford PV perovskite-silicon tandem solar cells, a research team at Fraunhofer Institute for Solar Energy Systems ISE has now successfully manufactured a glass-glass tandem PV module with 25 percent efficiency (related to designated illuminated area).

As the perovskite layer of the tandem cells is temperature-sensitive, the research team developed low-temperature processes for the interconnection and encapsulation of the solar cells that are also particularly gentle on the cells mechanically. The solar cells were interconnected using conductive bonding.

For the calibration measurements, CalLab PV Modules used a new multispectral solar simulator to determine the module efficiency. In order to make precise and reproducible statements about the tandem module’s power, both the perovskite and the silicon cell layers must be illuminated by different LED light sources under conditions that are as close as possible to those in which they produce electricity under natural sunlight. The efficiency was calculated using the designated area (da) of 1.68 square meters. As the currently standardized measurement methods are not fully transferable to this new technology, the method used was additionally validated with field measurements.