27 September 2012 Optical signatures of the interplay between intermolecular and intramolecular coupling in plastic semiconductors
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Abstract
Polymeric semiconductors such has regioregular poly(3-hexylthiophene) have electronic proprieties that can be tuned by proper control of the solid-state microstructure. We process thin films of P3HT of different molecular weight ranging from 2 kg/mol to 341 kg/mol. The polymer undergo a transition from a paraffinic, non-entangled microstructure to a two-phase microstructure defined by entangled chains embedded in amorphous regions at around 50 kg/mol. We observe an abrupt decrease in the intermolecular coupling from an average of ~20 meV for molecular weight below 50 kg/mol to ~5 meV above 50 kg/mol. We assign this decrease in the interchain coupling and associated free-exciton bandwidth at higher molecular weight to a transition from a one-phase morphology to a two-phase morphology defined above. In steady-state photoluminescence, we associate the lower Huang-Rhys factors at higher molecular weight to more planar backbone.
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Francis Paquin, Maciej Sakowicz, Natalie Stingelin, Carlos Silva, "Optical signatures of the interplay between intermolecular and intramolecular coupling in plastic semiconductors", Proc. SPIE 8459, Physical Chemistry of Interfaces and Nanomaterials XI, 845904 (27 September 2012); doi: 10.1117/12.939633; https://doi.org/10.1117/12.939633
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