Exploring Wide‐Range Alkyl Bridge Length Variations in Polymer Semiconductors: From Pristine to Blend Films for High‐Mobility Stretchable TFTs

The development of intrinsically stretchable thin-film transistors (TFTs) with high mobility is essential for next-generation deformable electronics, including wearable displays and bio-integrated systems. However, most approaches to improve stretchability in polymer semiconductors compromise charge transport due to disrupted molecular ordering. Here, we report a systematic exploration of wide-range of alkyl bridge length variations of donor-acceptor-type conjugated polymers to control crystallinity and morphology without altering the polymer backbone. We also propose a method to quantify the relative degree of crystallinity, enabling comparison across different polymer systems. When blended with an elastomer and aligned via solution shearing, the optimized polymer exhibited a maximum mobility of 6.4 cm² V^-1 s^-1 at 0% strain (V_DS = -40 V). The polymer stretchable device maintained measurable mobility (0.6 cm² V^-1 s^-1) at 100% strain under the perpendicular to the channel direction under a low V_DS of -10 V. Furthermore, wafer-scale photopatterning enabled fabrication of a 38-device intrinsically stretchable TFT array with high uniformity and an average mobility of 5.5 cm² V^-1 s^-1 at 0% strain. This work establishes a molecular design framework that elucidates the link between structure, mechanical resilience, and electrical performance, offering generalizable principles and a scalable platform for high-performance deformable electronics.