Shear-Enhanced Stretchable Polymer Semiconducting Blends for Polymer-based Field-Effect Transistors

Solution-sheared field-effect transistors based on the blend of the high-mobility donor-acceptor conjugated copolymer poly(diketopyrrolo[3,4-c]pyrrole-co-thieno[3,2-b]thiophene) (PDBT-co-TT) and the elastic polymer poly(styrene-butadiene-styrene) (SBS) are demonstrated for stretchable electronics. In this study, PDBT-co-TT serves as a charge transport layer, and the insulating polymer SBS with double bonds is used for improving elasticity. Through combination with solution shearing, the phase separation and charge transport properties of the PDBT-co-TT/SBS blends can be manipulated. Compared with the spin-coated PDBT-co-TT/SBS blends showing lower charge mobilities (~10−3 cm2 V−1 s−1), the solution-sheared polymer-blend films with the PDBT-co-TT content of 20% maintain high mobility (>0.1 cm2 V−1 s−1). The films with 60% PDBT-co-TT can even achieve mobility as high as 2 cm2 V−1 s−1, which is higher than the pristine conjugated polymer. Furthermore, as the SBS content increases, the dichroic ratios of the solution-sheared blends increase, indicating improved alignment of the conjugated polymer chains. The PDBT-co-TT/SBS blends exhibit great stretchability and high charge mobilities even under 100% strain due to their mesh-like morphology. Moreover, solution shearing not only improves polymer alignment but also controls surface morphology to enhance stretchability. This work reveals the importance of solution shearing in high-mobility stretchable polymer semiconductor blends.