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Viscoelastic polymer semiconductors have the potential to be effective components in stretchable electronics. These malleable materials provide a simple and effective approach to realize stretchable field effect transistors and sensors.[1] For successful operation, the polymer film must be able to withstand large cyclic strains while maintaining electrical properties. Here, we show that in the stretching process, the elastomer substrate plays a critical role in the mechanical response of the semiconductor film. In particular, we explore the role of adhesion and near-surface modulus of a PDMS elastomer on the ability to achieve stretchable PDPP-4T films. We also show the use of PDMS tension on the stability of the film. We find that the increase in near-surface modulus of the PDMS and maintaining the PDMS in tension limits film wrinkling under large cyclic strain, and that an increase adhesion greatly reduces film delamination and propensity to tear. We show that through proper engineering of the elastomer substrate, the PDD-4T film has a surface roughness consistently below 3 nm for a strain range of 50% and for over 100 strain cycles. The local morphology and charge transport of the semicrystalline DPP-4T is also characterized in detail and shown to vary in a systematic and stable manner under this large strain range. These results demonstrate the ability to use low glass transition temperature polymers for intrinsically stretchable semiconductors given appropriate interactions with adjacent elastomer layers. [1] T. Sun, B. O’Connor, et al, Adv. Electron. Mater. 1600388, 2017. |
