Realizing\nIntrinsically Stretchable Semiconducting\nPolymer Films by Nontoxic Additives

Abstract

Stretchable polymer semiconductors are essential materials\nto realize\nsoft skin-like electronics. However, most high-mobility semiconducting\npolymers suffer from poor stretchability and strain-dependent charge\ncarrier mobility. Herein, we report an approach to improve the stretchability\nof semiconducting polymers while maintaining charge carrier mobility.\nThe strain independent performance was accomplished by incorporating\na nontoxic small molecule, namely triacetin (TA), into high-mobility\nconjugated polymers. We observed that TA molecules substantially increased\nthe stretchability of the high-mobility semiconducting polymer diketopyrrolopyrrole-thienyl-vinyl-thiophene\n(DPP-TVT), with a crack onset strain >100%, while the neat DPP-TVT\npolymer only shows a low crack onset strain <25%. The organic field-effect\ntransistor (OFET) devices fabricated using the TA blend films maintain\nsimilar charge carrier mobility compared to the neat DPP-TVT-based\ndevices. The influences of TA additive were further characterized,\nwhich included reduced glass transition temperature of polymer backbones,\ndecreased modulus, and breakage of the polymer chain aggregations.\nThe TA additive functions as a plasticizer residing in between lamellae\nlayers of semiconducting polymers, which helps to preserve the crystalline\nmolecular packing under deformation. We demonstrated the applicability\nof this approach by improving the stretchability of various semiconducting\npolymers using TA and its analog tricaproin. Last, a stretchable OFET\narray was fabricated with TA blended films, and it showed a well-maintained\ncharge carrier mobility even after 1000 stretch–release cycles\nat 50% strain.