Oligothiophene wires: impact of torsional conformation on the electronic structure
| Autor: | Alejandro L. Briseno, George V. Nazin, James S. Prell, Lei Zhang, Benjamen N. Taber, Christian F. Gervasi, Dmitry A. Kislitsyn, Stefan C. B. Mannsfeld |
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| Rok vydání: | 2016 |
| Předmět: |
Chemistry
General Physics and Astronomy 02 engineering and technology Electronic structure 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences law.invention Organic semiconductor Crystallography Atomic orbital law Molecule Molecular orbital Density functional theory Physical and Theoretical Chemistry Scanning tunneling microscope 0210 nano-technology HOMO/LUMO |
| Zdroj: | Physical Chemistry Chemical Physics. 18:4842-4849 |
| ISSN: | 1463-9084 1463-9076 |
| DOI: | 10.1039/c5cp07092a |
| Popis: | Charge transport in polymer- and oligomer-based semiconductor materials depends strongly on the structural ordering of the constituent molecules. Variations in molecular conformations influence the electronic structures of polymers and oligomers, and thus impact their charge-transport properties. In this study, we used Scanning Tunneling Microscopy and Spectroscopy (STM/STS) to investigate the electronic structures of different alkyl-substituted oligothiophenes displaying varied torsional conformations on the Au(111) surface. STM imaging showed that on Au(111), oligothiophenes self-assemble into chain-like structures, binding to each other via interdigitated alkyl ligands. The molecules adopted distinct planar conformations with alkyl ligands forming cis- or trans- mutual orientations. For each molecule, by using STS mapping, we identify a progression of particle-in-a-box-like states corresponding to the LUMO, LUMO+1 and LUMO+2 orbitals. Analysis of STS data revealed very similar unoccupied molecular orbital energies for different possible molecular conformations. By using density functional theory calculations, we show that the lack of variation in molecular orbital energies among the different oligothiophene conformers implies that the effect of the Au-oligothiophene interaction on molecular orbital energies is nearly identical for all studied torsional conformations. Our results suggest that cis-trans torsional disorder may not be a significant source of electronic disorder and charge carrier trapping in organic semiconductor devices based on oligothiophenes. |
| Databáze: | OpenAIRE |
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