Organic solar cells set world record

A world record of 10.7% efficiency for an organic photovoltaic cell has been claimed by German maker Heliatek. The measurement, by an independent testing facility, was made on a 1.1 cm² array and also confirmed good low light and high temperature performance of OPV cells compared with traditional solar technologies.

At the heart of this achievement is said to be the company-developed family of small organic molecules - oligomers - developed and synthesised at its own laboratory in Ulm. Dr Martin Pfeiffer, cofounder and CTO of the company, said this is the only solar organisation in the world that uses the deposition of small organic molecules in a low-temperature, roll-to-roll vacuum process.

“Our solar tandem cells are made of nanometres-thin layers of high purity and uniformity. This enables us to literally engineer the cell architecture to systematically improve efficiency and lifetime.”

The measurement results for low light established that the efficiency not only remains constant but even increases gradually. At an irradiation of 100 W/m² the efficiency is 15% higher compared with the standard efficiency measured at 1000 W/m². Additionally, the measurements at high temperatures confirmed that the efficiency remains constant. This behaviour is unique for OPV technology in contrast to traditional solar technology where efficiency drops 15 to 20% at elevated temperatures.

First outdoor tests have shown that the harvesting factor of Heliatek’s organic solar cells is 15 to 25% higher than crystalline and thin film solar.