64

nanotimes News in Brief Organic Electronics //

Improving Organic and Molecular Electronic Devices © Based on Material by LBNL

R

esearcher at Lawrence Berkeley National Labo- ratory, Berkeley, USA, has provided the first ex-

perimental determination of the pathways by which electrical charge is transported from molecule-to- molecule in an organic thin film. Their results also show how such organic films can be chemically modified to improve conductance.

“We have shown that when the molecules in organic thin films are aligned in particular directions, there is much better conductance,” says Miquel Salmeron, a leading authority on nanoscale surface imaging who directs Berkeley Lab’s Materials Sciences Divisi- on and who led this study. “Chemists already know how to fabricate organic thin films in a way that can achieve such an alignment, which means they should be able to use the information provided by our methodology to determine the molecular alignment and its role on charge transport across and along the molecules. This will help improve the performances of future organic electronic devices.”

In this study, Salmeron and his colleagues used elec- tron diffraction patterns to map the crystal structures of molecular films made from monolayers of short versions of commonly used polymers containing long chains of thiophene units. They focused specifically on pentathiophene butyric acid (5TBA) and two of its derivatives (D5TBA and DH5TBA) that were indu- ced to self-assemble on various electron-transparent

12-03 :: March/April 2012

Scanning transmission electron microscopy image of an organic thin film deposited on a silicon nitride membrane. Yellow arrows indicate the lattice orientation of each crystalline domain. Green circles mark polycrystalline areas. © Berkeley Lab’s Molecular Foundry

substrates. Pentathiophenes – molecules containing a ring of four carbon and one sulfur atoms – are members of a well-studied and promising family of organic semiconductors.

“Chemists and engineers have been using their intu- ition and trial-and-error testing to make progress in