The Effect of Ring Expansion in Thienobenzo[b]indacenodithiophene Polymers for Organic Field-Effect Transistors
[2];
[6];
[1];
[4];
[7]
- King Abdullah Univ. of Science and Technology (KAUST), Thuwal (Saudi Arabia)
- Imperial College London (United Kingdom)
- Univ. of Cambridge (United Kingdom)
- Univ. of Warwick, Coventry (United Kingdom)
- Stanford Univ. CA (United States)
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- King Abdullah Univ. of Science and Technology (KAUST), Thuwal (Saudi Arabia); Imperial College London (United Kingdom)
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 cm2 V-1 s-1, lower than the performance of IDT-BT (~1.5 cm2 V-1 s-1). 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.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22), Solar Photochemistry Program; National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC36-08GO28308; AC02-76SF00515; EP/G037515/1; EP/M005143/1; EP/M005141/1; 643791; 610115; 1808401
- OSTI ID:
- 1579641
- Alternate ID(s):
- OSTI ID: 1596274
- Report Number(s):
- NREL/JA-5F00-74867; TRN: US2102236
- Journal Information:
- Journal of the American Chemical Society, Vol. 141, Issue 47; ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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journal | April 2020 |
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