Semiconducting polymer thin films are essential elements of soft electronics for both wearable and biomedical applications1,2,3,4,5,6,7,8,9,10,11. However, high-mobility semiconducting polymers are usually brittle and can be easily fractured under small strains (<10%)12,13,14. Recently, the improved intrinsic mechanical properties of semiconducting polymer films have been reported through molecular design15,16,17,18 and nanoconfinement19. Here we show that engineering the interfacial properties between a semiconducting thin film and a substrate can notably delay microcrack formation in the film. We present a universal design strategy that involves covalently bonding a dissipative interfacial polymer layer, consisting of dynamic non-covalent crosslinks, between a semiconducting thin film and a substrate. This enables high interfacial toughness between the layers, suppression of delamination and delocalization of strain. As a result, crack initiation and propagation are notably delayed to much higher strains. Specifically, the crack-onset strain of a high-mobility semiconducting polymer thin film improved from 30% to 110% strain without any noticeable microcracks. Despite the presence of a large mismatch in strain between the plastic semiconducting thin film and elastic substrate after unloading, the tough interface layer helped maintain bonding and exceptional cyclic durability and robustness. Furthermore, we found that our interfacial layer reduces the mismatch of thermal expansion coefficients between the different layers. This approach can improve the crack-onset strain of various semiconducting polymers, conducting polymers and even metal thin films.
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This work is supported by Samsung Electronics. J.K. acknowledges support from the National Research Foundation of Korea through grant nos. 2021R1C1C1011116 and 2021M3H4A1A03048658. J.M. acknowledges financial support from Samsung Scholarship. L.J. acknowledges support from the National Science Foundation through grant no. CMMI-1925790. We acknowledge J. Hutchinson of Harvard University for the insightful discussions. Part of this work was performed at the Stanford Nano Shared Facilities (SNSF).
The authors declare no competing interests.
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Kang, J., Mun, J., Zheng, Y. et al. Tough-interface-enabled stretchable electronics using non-stretchable polymer semiconductors and conductors. Nat. Nanotechnol. (2022). https://doi.org/10.1038/s41565-022-01246-6