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Understanding the key factors influencing the mechanical and electrical properties of semiconducting polymers is crucial to the development of stretchable electronics. In this work, a high-mobility diketopyrrolopyrrole-based conjugated polymer with varied number-average molecular weights (Mn) was used as the model system to explore the impact of molecular weight on the electrical and mechanical properties. Higher-Mn films are more ductile and stretchable. Both hole mobilities of thin-film transistors and elastic modulus become maximum at a moderate Mn of 88 kg/mol. It was found that film continuity, entanglements, and relative degree of crystallinity are critical factors for approaching the best device performance and highest elastic modulus. The transition molecular weight of a given polymer semiconductor is the key to achieving stretchable high-mobility transistors that are practically useful. This work would help to offer guidance to manipulate the mechanical and electrical properties for other polymer semiconductors.
Pei et al. (Tue,) studied this question.