This is an image of the PCBM nanoribbons, which comprise four PCBM molecules organized side by side, with grey balls representing the fullerene molecules. Image: Umeå University.
This is an image of the PCBM nanoribbons, which comprise four PCBM molecules organized side by side, with grey balls representing the fullerene molecules. Image: Umeå University.

Physicists at Umeå University in Sweden, together with researchers at the University of California, Berkeley, US, have synthesized a unique and novel type of nanoribbon that could enhance the efficiency of organic solar cells. The results have been published in ACS Nano.

The nanoribbons are comprised of molecules known as [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). In practice, this is a fullerene molecule (a football-shaped carbon molecule) with an attached side arm to increase its solubility. PCBM molecules are commonly used in organic solar cells, since they have a very good ability to transport free electrons ‘generated’ by sunlight.

The researchers at Umeå University and UC Berkeley have now developed a method to arrange such molecules into thin, crystalline nanoribbons that are only 4nm wide. The nanoribbons are grown with high efficiency in a solution process and have a unique morphology with zigzag-shaped edges.

"It is a very intriguing material and the method is quite simple," says Thomas Wågberg, associate professor at the Department of Physics, who led the study. "The material resembles the more commonly known graphene nanoribbons, but in our material each carbon atom is 'replaced' by a [PCBM] molecule."

This is the first time that structures with such small dimensions have been produced with this type of molecule, while the dimensions of the nanoribbons suggest that they should make effective ‘electronic highways’ in organic solar cells. An organic solar cell usually consists of two types of material, one that conducts the electrons and one that conducts the ‘holes’ that are left behind when an electron is boosted out of an atom by incoming sunlight. The electron conductor in organic solar cells should ideally form long pathways to the electrode and be thinner than 10–15nm. The newly developed PCBM nanoribbons fulfil all these requirements.

"Together with Professor Ludvig Edman's group at the Department of Physics at Umeå University, we are now investigating this material further as a potential component in organic solar cells in the hope of making such devices more efficient," says Wågberg.

This story is adapted from material from Umeå University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.