Backbone Torsion Engineering for Highly Stretchable Polymer Semiconductors

Polymer semiconductors enable the development of stretchable devices in skin-like wearable electronics. However, a formidable challenge stem from breaking the trade-off between stretchability and charge carrier mobility for these semiconductor devices. Instead of introducing conjugation breakers or flexible blocks, we strategically incorporated nonplanar and rigid 5,11-bis(2-octyldodecyl)-2,8-di(thiophen-2-yl)-5,11-dihydroindolo[3,2-b]carbazole (TICZ) units into conjugated polymer backbones at varying modification ratios to deliberately induce backbone twisting. This structural distortion effectively suppresses polymer chain aggregation, reduces crystallite size and overall film crystallinity, and ultimately enhances mechanical stretchability. Meanwhile, the excellent charge transport properties were achieved because of the maintenance of conjugated polymer backbone. The designed polymer demonstrates exceptional balance of electrical and mechanical properties, maintaining charge carrier mobility (0.7 cm² V^-1 s^-1) comparable to the reference material while exhibiting significantly larger crack onset strains (120%) and a reduced tensile modulus. Therefore, fully stretchable transistors remain stable charge carrier mobility even under extreme tensile strain of 100% applied parallel to the charge transport direction, while also demonstrating exceptional cyclic mechanical stability. Therefore, backbone torsion engineering represents a pivotal design paradigm for high-performance stretchable semiconducting polymers.