Methylated conjugated polymers based on diketopyrrolopyrrole and dithienothiophene for high performance field-effect transistors

• Methylated polymers based on diketopyrrolopyrrole and dithienothiophene were designed for field-effect transistors.
• Methylated polymers were found to show high hole mobilities up to 5.32 cm2 V−1 s−1.
• Asymmetrically methylated polymers with highest hole mobility show “face-on” orientation in thin films.

In this work, a series of conjugated polymers based on diketopyrrolopyrrole (DPP) and dithienothiophene were designed for application in field-effect transistors (FETs). Owing to the synthetic nature of DPP units, the DPP polymers here contain different aromatic linkers with thiophene and methylthiophene, resulting in non-methylated and methylated DPP polymers. Methylated DPP polymers were found to show good crystalline properties and provide high hole mobilties up to 5.32 cm2 V−1 s−1 in FETs, while non-methylated polymer exhibits a hole mobility of 3.16 cm2 V−1 s−1. Especially, the polymer containing asymmetric linkers presents “face-on” orientation in thin films but provides the highest mobility. Our results reveal that the polymers incorporating methyl units as side chains can be used to realize high carrier mobility in FETs.

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