Analysis drives up efficiency of large area organic solar cells

December 01, 2016 // By Nick Flaherty
Researchers at the University of Surrey have analysed how low cost materials combine to achieve a record power conversion efficiency of 6.7% for large area organic solar cells.

The research is part of a four-year European Commission FP7 programme called SMARTONICS that is aimed at developing large-scale pilot lines for the fabrication and printing of organic polymer solar cells. Led by the University of Surrey's Advanced Technology Institute (ATI), the four year project includes Oxford University in the UK, Aristotle University of Thessaloniki in Greece), and University of Stuttgart in Germany and finishes this month.

The research looks at the dependencies between the chemical and physical properties of the photoactive layer's building blocks within organic solar cells to determine the efficiency of these solar cells. By using a well-known and low cost electron donating material, P3HT, in combination with an electron accepting material, ICBA, for the photosensitive layer of the organic solar cells, the research team discovered that different ICBA samples have different arrnagements of atoms. This is critical for the formation and spatial arrangement of P3HT and ICBA and lead to varying power conversion efficiencies.

Tailoring the fabrication process based on these findings, the research team were able to improve the efficiency of their solar cells from 2.2% up to 6.7%. This is one of the highest efficiencies to have been reported for P3HT blends on a large-area device, and compares to 17% for cells using perovskite materials.

"Solar cells made of organic materials have a number of benefits over traditional inorganic solar cells," said Professor Ravi Silva, Director of the ATI at Surrey. "Not only are they flexible, lightweight and environmentally-friendly, they are also design-friendly because they can be semi-transparent and printed in different colours and shapes. In addition, in contrast to their inorganic competitors, they convert efficiently indirect sunlight, which makes them an ideal material to power devices on the move, such as for the Internet of Things."

"The research represents a significant step forward in the understanding of the