Scientists from the University of Surrey have achieved record power conversion efficiencies for large-area organic solar cells. In recent years, researchers have been trying to increase the efficiency of these solar cells in order to make them available for commercial applications, like integration into the glass façade of a building to generate electricity to power the building.
The University of Surrey’s Advanced Technology Institute (ATI) led the research in collaboration with Oxford University, University of Stuttgart (Germany) and Aristotle University of Thessaloniki (Greece). The project is part of a four-year European Commission FP7 programme, SMARTONICS, intended for developing large-scale pilot lines for the production and printing of organic polymer solar cells.
The research, published in Advanced Electronic Materials, shows that dependencies between the physical and chemical properties of the photoactive layer’s building blocks inside organic solar cells determine the solar cells’ efficiency.
The research team used a low-cost and well-known electron donating material (P3HT) along with an electron accepting material (ICBA) for the organic solar cells’ photosensitive layer and discovered that different ICBA samples contain dissimilar isomeric mixtures (isomers are molecules that have the same number of atoms of each element, but they are arranged differently with the atoms).
These features are crucial for the formation kinetics as well spatial arrangement of P3HT and ICBA in their photosensitive blend, leading to varying power conversion efficiencies.
Modifying the fabrication process based on these research findings, the scientists were able to improve the efficiency of solar cells from 2.2% to 6.7%. This is one of the record efficiencies to have been reported for the P3HT combination on a large-area device.
Solar cells made of organic materials have a number of benefits over traditional inorganic solar cells – and more so when the organic is P3HT, the fruit fly for organic solar cells. 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. Our group is looking to expand research in this field, with more PhD students and researchers, which will have such a positive impact on society.
Professor Ravi Silva, Director of the ATI
PhD student Dimitar Kutsarov, the paper’s lead author, said, “The research represents a significant step forward in the understanding of the characteristics of materials with isomeric properties, which will lead to a future improvement of the efficiency of organic solar cells. We know now how important the spatial arrangement of the isomeric molecules is and will, therefore, be able to push the efficiency of P3HT-based solar cells further. Our findings will be used for the fabrication of meters long organic solar cells as part of the successful completion of the collaborative European project SMARTONICS.”