Dipole-Tailored Isomeric Linker Enables Decoupling of Aggregation and Crystallinity in Conjugated Polymers for Stretchable Transistors and Photodiodes

The microstructure of conjugated polymers critically influences their mechanical and electronic properties. Reducing crystallinity is a common approach to improve stretchability but often leads to diminished chain aggregation, which impairs charge transport. To address this trade-off, we introduce a dipole modulation strategy to decouple aggregation from crystallinity in conjugated polymers. A series of dipole-tailored isomeric linkers (DTLs), namely, 2,6-DTL, 3,5-DTL, and 2,4-DTL, are synthesized by varying the position of an alkoxy substituent on a benzene core and flanked by thiophene units, yielding linkers with increasing dipole moments. These linkers are incorporated into a diketopyrrolopyrrole (DPP)-based polymer backbone to regulate dipole moment and chain packing. The PDPP-(2,4)-DTL polymer, whose linker possesses the highest dipole moment and most asymmetric geometry, exhibits reduced long-range crystallinity and enhanced short-range aggregation. This optimized microstructure leads to a 4-fold increase in crack onset strain and a 1.5-fold enhancement in field-effect mobility compared to the reference polymer. Subsequently, PDPP-(2,4)-DTL is blended with the nonfullerene acceptor Y7 to form the bulk heterojunction layer of a stretchable organic photodiode. The resulting device exhibits higher external quantum efficiency (EQE) and detectivity (<i>D</i>*) relative to the control, maintains a <i>D</i>* above 10¹¹ Jones under 80% strain, and retains a stable photoresponse after hundreds of stretching cycles. These findings highlight dipole modulation as an effective strategy to tailor polymer microstructure and simultaneously enhance mechanical and electronic properties.