Regioregular, yet ductile and amorphous indacenodithiophene-based polymers with high-mobility for stretchable plastic transistors

Abstract

In the past decade, various high-performing π-conjugated polymers based on axisymmetric cyclopentadithiophene (CDT) and centrosymmetric indacenodithiophene (IDT) units have been thoroughly studied for use in organic field-effect transistors. However, no comparative set of data between CDT- and IDT-based polymers is available with a focus on relevant change in optoelectronic and morphological properties. Herein, we report the synthesis and characterization of four regioregular, well-defined donor–acceptor polymers (P1–P4), comprising different compositions of CDT and IDT donors in conjugation with the asymmetric 5-fluoro-2,1,3-benzothiadiazole acceptor that is precisely oriented in the regular pattern along the backbone. Morphological analyses of the above polymer series show that exclusive CDT donor-containing P1 is semicrystalline, whereas the others (IDT donor-containing ones) are near-amorphous in nature. Comparatively, IDT donor-containing polymers have superior hole mobilities; in particular, exclusive IDT donor-containing polymer P4 offers a high mobility of 1.67 cm² V⁻¹ s⁻¹. In addition, the near-amorphous characteristics render the IDT donor-containing polymer films highly ductile and stretchable. Such superior features, which are associated with excellent charge transport and ductility, demonstrate a promising possibility for application in viable stretchable electronics.