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The Effect of Ring Expansion in Thienobenzo[ b ]indacenodithiophene Polymers for Organic Field-Effect Transistors.
- Source :
-
Journal of the American Chemical Society [J Am Chem Soc] 2019 Nov 27; Vol. 141 (47), pp. 18806-18813. Date of Electronic Publication: 2019 Nov 18. - Publication Year :
- 2019
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Abstract
- A fused donor, thienobenzo[ b ]indacenodithiophene ( TBIDT ), was designed and synthesized using a novel acid-promoted cascade ring closure strategy, and then copolymerized with a benzothiadiazole ( BT ) monomer. The backbone of TBIDT is an expansion of the well-known indacenodithiophene ( IDT ) unit and was expected to enhance the charge carrier mobility by improving backbone planarity and facilitating short contacts between polymer chains. However, the optimized field-effect transistors demonstrated an average saturation hole mobility of 0.9 cm <superscript>2</superscript> V <superscript>-1</superscript> s <superscript>-1</superscript> , lower than the performance of IDT-BT (∼1.5 cm <superscript>2</superscript> V <superscript>-1</superscript> s <superscript>-1</superscript> ). Mobilities extracted from time-resolved microwave conductivity measurements were consistent with the trend in hole mobilities in organic field-effect transistor devices. Scanning tunneling microscopy measurements and computational modeling illustrated that TBIDT-BT exhibits a less ordered microstructure in comparison to IDT-BT . This reveals that a regular side-chain packing density, independent of conformational isomers, is critical to avoid local free volume due to irregular packing, which can host trapping impurities. DFT calculations indicated that TBIDT-BT , despite containing a larger, planar unit, showed less stabilization of planar backbone geometries in comparison to IDT-BT . This is due to the reduced electrostatic stabilizing interactions between the peripheral thiophene of the fused core and the BT unit, resulting in a reduction of the barrier to rotation around the single bond. These insights provide a greater understanding of the general structure-property relationships required for semiconducting polymer repeat units to ensure optimal backbone planarization, as illustrated with IDT -type units, guiding the design of novel semiconducting polymers with extended fused backbones for high-performance field-effect transistors.
Details
- Language :
- English
- ISSN :
- 1520-5126
- Volume :
- 141
- Issue :
- 47
- Database :
- MEDLINE
- Journal :
- Journal of the American Chemical Society
- Publication Type :
- Academic Journal
- Accession number :
- 31613619
- Full Text :
- https://doi.org/10.1021/jacs.9b09367