Researchers at Fraunhofer ISE Announce 15.8% Efficiency for Organic Solar Cells

The cells are eco-friendly, cost-effective, and versatile to use


Researchers at the Fraunhofer Institute for Solar Energy Systems ISE (Fraunhofer ISE) and the Materials Research Center FMF at the University of Freiburg have announced efficiency improvement for an organic solar cell with a one-square-centimeter area, boasting a record efficiency of 15.8% which has surpassed their previous record set in September 2020, of 14.9%.

Organic photovoltaics (OPV) have various solar energy applications due to their eco-friendly and cost-effective production, as well as their versatility with flexible and potentially transparent solar cells.

Research institutions worldwide are dedicated to enhancing the efficiency and scalability of organic solar cells to facilitate their market breakthrough.

Dr. Uli Würfel, department head at Fraunhofer ISE and group head at the Materials Research Center FMF, University of Freiburg, lead the organic solar cell research. He explains the key factor behind their achievement, “We achieved the improvement in the record-breaking solar cell primarily by applying an anti-reflection coating, which allows more light to be absorbed in the photoactive layer of the cell, thus generating a higher current.”

The thin-film system used in this advancement, developed through in-house research at Fraunhofer ISE, employs a sputtering process.

Prof. Dr. Andreas Bett, Institute Director at Fraunhofer ISE, emphasizes the strength of cross-thematic collaboration within the institute, as different photovoltaic technologies and their manufacturing processes inspire collaboration and synergy effects.

Moreover, the anti-reflection coating technology is not limited to reducing reflection; it is also employed in developing electrodes for semi-transparent organic solar cells. These cells consist of a photoactive organic layer applied to a back electrode that allows visible light to pass through while strongly reflecting near-infrared light back into the solar cell, where it is absorbed and converted into electricity.

During the study, the scientists explored materials that offer high transparency to visible light for the absorber layer and both front and rear electrodes.

By selecting organic semiconductors that absorb primarily infrared light, transparent solar cells can be developed for applications such as windows and transparent protective covers for crops.

This enables the combination of weather and overheating protection with effective power generation. However, significant development steps remain to bring such products to market readiness.

The study is funded by the German Federal Ministry of Economic Affairs and Climate Protection (BMWK).

Recently, Japan-based Toshiba Corporation’s researchers announced a method of layering a transparent solar cell over a standard silicon cell to develop an efficient, low cost and reliable tandem solar cell to raise the solar module output.

In June, researchers from the Fraunhofer ISE’s Centre for High-Efficiency Solar Cells claimed a power conversion efficiency of 47.6% in a multijunction solar cell (III-V) using an anti-reflection coating at a concentration of 665 suns (heat concentration levels equalling 665 suns).