Cation-Dependent Poly(benzimidazobenzophenanthroline):Crown Ether Polymer Blends in n-Type Organic Electrochemical Transistors

N-type organic electrochemical transistors (OECTs) hold promise for cation-responsive bioelectronics; however, their application in this area lags behind that of their p-type counterparts. Here, we introduce a BBL:PVB18C6 polymer blend synthesized via acid-mediated in situ polymerization of vinylbenzo-18-crown-6 (VB18C6) in the presence of poly(benzimidazobenzophenanthroline) (BBL) in methanesulfonic acid, enabling homogeneous integration of crown ether motifs selective for K+. Quantitative integration of the X-ray photoemission spectra provided direct evidence of differential cation uptake in BBL and BBL:PVB18C6, underscoring the cation recognition capability of the polymer blend. When employed as the channel in OECTs, BBL:PVB18C6 devices exhibit enhanced drain current, 76% higher volumetric capacitance in KCl (395 F cm–3) compared to NaCl (225 F cm–3), and concentration-dependent response toward K+ over Na+, while retaining excellent operational stability. This work establishes a strategy for functionalizing BBL with ion-selective motifs, enabling the development of cation-dependent n-type OECTs.