High‐Performance Organic Electrochemical Transistors Achieved by Optimizing Structural and Energetic Ordering of Diketopyrrolopyrrole‐Based Polymers

Abstract For optimizing steady‐state performance in organic electrochemical transistors (OECTs), both molecular design and structural alignment approaches must work in tandem to minimize energetic and microstructural disorders in polymeric mixed ionic–electronic conductor films. Herein, a series of poly(diketopyrrolopyrrole)s bearing various lengths of aliphatic–glycol hybrid side chains (PDPP‐ m EG; m = 2–5) is developed to achieve high‐performance p‐type OECTs. PDPP‐4EG polymer with the optimized length of side chains exhibits excellent crystallinity owing to enhanced lamellar and backbone interactions. Furthermore, the improved structural ordering in PDPP‐4EG films significantly decreases trap state density and energetic disorder. Consequently, PDPP‐4EG‐based OECT devices produce a mobility–volumetric capacitance product ([ µC *]) of 702 F V −1 cm −1 s −1 and a hole mobility of 6.49 ± 0.60 cm 2 V −1 s −1 . Finally, for achieving the optimal structural ordering along the OECT channel direction, a floating film transfer method is employed to reinforce the unidirectional orientation of polymer chains, leading to a substantially increased figure‐of‐merit [ µC *] to over 800 F V −1 cm −1 s −1 . The research demonstrates the importance of side chain engineering of polymeric mixed ionic–electronic conductors in conjunction with their anisotropic microstructural optimization to maximize OECT characteristics.