Molecular Nanoribbons as Electronic Highways

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One-dimensional (1D) zigzag [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) nanoribbons are produced by folding two-dimensional ultrathin PCBM nanosheets in a simple solvent process. The unique 1D PCBM nanostructures exhibit uniform width of 3.8 ± 0.3 nm, equivalent to four PCBM molecules, and lengths of 20–400 nm. These nanoribbons show well-defined crystalline structure, comprising PCBM molecules in a hexagonal arrangement without trapped solvent molecules. First-principle calculations and detailed experimental characterization provide an insight into the structure and formation mechanism of the 1D PCBM nanoribbons. Given their dimensions and physical properties, we foresee that these nanostructures should be ideal as acceptor material in organic solar cells.

One-dimensional (1D) zigzag [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) nanoribbons are produced by folding two-dimensional ultrathin PCBM nanosheets in a simple solvent process. The unique 1D PCBM nanostructures exhibit uniform width of 3.8 ± 0.3 nm, equivalent to four PCBM molecules, and lengths of 20–400 nm. These nanoribbons show well-defined crystalline structure, comprising PCBM molecules in a hexagonal arrangement without trapped solvent molecules. First-principle calculations and detailed experimental characterization provide an insight into the structure and formation mechanism of the 1D PCBM nanoribbons. Given their dimensions and physical properties, we foresee that these nanostructures should be ideal as acceptor material in organic solar cells.

Physicists have developed a method to synthesize a unique and novel type of material which resembles a graphene nanoribbon but in molecular form which may be important for further development of organic solar cells. The nanoribbons are composed of molecules with the chemical formula [6,6]-phenyl-C61-butyric acid methyl ester ie PCBM, and in practice it is a fullerene 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 solar light.

UmeÃ¥ and UC Berkeley have developed a method to arrange such molecules into thin, crystalline nanoribbons that are only 4 nm wide. The nanoribbons are grown in a solution process with quite high efficiency and all nanoribbons have a unique morphology with zigzag edges. “It is a very intriguing material and the method is quite simple. The material resembles the more commonly known graphene nanoribbons, but in our material each carbon atom is ‘replaced’ by a molecule,” says A/Prof WÃ¥gberg

It is the 1st time that structures with so small dimensions have been produced with this type of molecule, and the dimensions of the nanoribbons suggest that they should be ideal as “electronic highways” in organic solar cells. An organic solar cell usually consists of 2 types of material, one that conducts the electrons and one that conducts the “holes” that are left behind when the electron gets an energy boost from the incoming solar light.

An electron conductor in organic solar cells should ideally form long pathways to the electrode but concurrently be thinner than 10-15 nanometres. The newly developed PCBM nanoribbons fulfil all these requirements. “Together with professor Ludvig Edman’s group at the Department of Physics at UmeÃ¥ 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 Thomas WÃ¥gberg. http://pubsdc3.acs.org/doi/10.1021/acsnano.5b04972  http://www.umu.se/english/about-umu/news-events/news/newsdetailpage/molecular-nanoribbons-as-electronic-highways.cid256532