The Dependence of Regioregular Poly(3-Hexylthiophene) Film Morphology and Field-Effect Mobility on Molecular Weight
- SLAC
Morphological characterization has been used to explain the previously observed strong correlation between charge carrier mobility measured with thin-film transistors and the number-average molecular weight (MW) of the conjugated polymer regioregular poly(3-hexylthiophene). Atomic force microscopy and x-ray diffraction show that the low mobility, low MW films have a highly ordered structure composed of nanorods and the high mobility, high MW films have a less ordered, isotropic nodule structure. Modifying the morphology for a constant MW by changing the casting conditions or annealing the samples strongly affects the charge transport and morphology in the low mobility, low MW films, but has little effect on the high MW films. In-plane grazing incidence x-ray scattering shows the in-plane {pi}-stacking peak increases when the mobility increases for a constant MW. When the MW is changed, this correlation breaks down, confirming that in-plane {pi}-stacking does not cause the mobility-MW relationship. We believe a combination of disordered domain boundaries and inherent effects of chain length on the electronic structure cause the mobility-MW relationship.
- Research Organization:
- Stanford Linear Accelerator Center (SLAC), Menlo Park, CA
- Sponsoring Organization:
- SC
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 839719
- Report Number(s):
- SLAC-PUB-10918
- Country of Publication:
- United States
- Language:
- English
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