A Modular Blending Strategy for Synergistic Tuning of Microstructure and Performance in Organic Electrochemical Transistors

Comprehensive Summary The rapid advancement of organic mixed ionic‐electronic conductors (OMIECs) has driven steady improvements in organic electrochemical transistor (OECT) performance. However, achieving an optimal balance between charge‐carrier mobility ( μ ) and volumetric capacitance (C*) remains a fundamental challenge, particularly when relying on chemical copolymerization strategies to fine‐tune glycolated side‐chain content. Such approaches are often hindered by synthetically demanding routes and pronounced batch‐to‐batch variability, which impede the establishment of robust structure‐property relationships. Herein, we introduce a physical blending strategy: glycolated and alkylated donor‐acceptor (D‐A) polymers are blended across a compositional gradient to yield a series of films with systematically varied hydrophilic/hydrophobic side‐chain ratios. We comprehensively investigate how the blend ratio governs electrochemical doping kinetics, nanoscale film morphology, and OECT device metrics. Critically, varying the glycolated/alkylated polymer ratio induces continuous, nanoscale phase separation, yielding a morphologically integrated dual‐channel architecture that simultaneously facilitates ion transport through hydrophilic domains and electron transport through interconnected hydrophobic pathways. Importantly, this physical blending approach circumvents the synthetic complexity of copolymer design, enabling precise, modular tuning of side‐chain composition and device optimization using only two well‐defined parent polymers. Our strategy thus establishes a scalable, reproducible, and highly tunable approach for engineering high‐performance OECT channel materials.