Benzodithiophene and benzotrithiophene-based conjugated polymers for organic thin-film transistors application: Impact of conjugated- and acyl-side chain

• Benzodithiophene and benzotrithiophene-based conjugated polymers have been synthesized.
• The conjugated- and acyl-side chain substituent had strong impact of on polymer-packing order structures.
• The highest mobility of 1.70 × 10−3 cm2 V−1 s−1 was obtained for polymer-based devices.

A series of benzodithiophene (BDT) and benzotrithiophene (BTT)-based conjugated polymers (P1–P4), with/without conjugated- and acyl-side chain, have been synthesized by Stille cross-coupling reaction. Their thermal, photophysical, electrochemical properties, devices performances, and microstructure have been investigated. Conjugated-side chain can significantly raise the thermal stability and acyl-side chain can lower HOMO/LUMO energy levels. Organic thin-film transistors (OTFTs) based on conjugated polymers were fabricated and the transistor electrical characterization showed the device performance was sensitive to the conjugated- and acyl-side chain substituent of polymers. A maximum hole mobility of 1.70 × 10−3 cm2 V−1 s−1 was obtained for P1-based devices, which is an order of magnitude higher than those of P3 and P4-based devices. The corresponding microstructures were investigated by grazing-incidence X-ray diffraction (GIXD) to correlate with conjugated- and acyl-side chain dependent carrier mobility of P1–P4. The results showed that the conjugated- and acyl-side chain have an impact on the polymer packing models and device performances.

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