High‐Performance Stretchable Field‐Effect Transistors Based on Intrinsically Flexible n‐Type Partially Conjugated Polymers Synthesized via Aldol Polycondensation

Two intrinsically flexible conjugated polymers, PBT‐90 and PFBT‐90 , were designed and synthesized via aldol polycondensation. Both polymers incorporate a novel double‐flexible‐node unit, 5,5'‐bis(1,1,2,2‐tetrafluoro‐2‐(thiophen‐2‐yl)ethyl)‐2,2'‐bithiophene, which can reduce brittleness and enhance recoverability in both bulk polymers and processed films. Both polymers displayed n ‐type charge transport in transistors fabricated on a polyethylene terephthalate substrate, achieving high electron mobilities ( µ e ) of 3.85 and 4.56 cm 2 V −1 s −1 for PBT‐90 and PFBT‐90 , respectively, only slightly inferior to 5.44 and 6.37 cm 2 V −1 s −1 of their fully conjugated analogues, PBT‐100 and PFBT‐100 . Utilizing a self‐developed PET/CYTOP/AlO x three‐layer thin film transfer process, combined with orthogonal solvent design and interlayer protection strategies, we fabricated high‐performance stretchable transistors. The PFBT‐90 ‐based devices exhibited a record‐high µ e of 3.51 cm 2 V −1 s −1 in the pristine state. Under 100% strain, they retained a µ e > 2.86 cm 2 V −1 s −1 (>80% retention). The remarkable device performance originates from its suitable frontier molecular orbitals structure, low backbone glass transition temperature, and well‐balanced finitely conjugated backbone, where rigid conjugated segments ensure highly efficient charge carrier transport and flexible nonconjugated segments dissipate stress. Our findings offer a pivotal molecular design strategy and a versatile fabrication process for advanced stretchable organic electronics.