Channel Confinement: A Novel Approach to Tackle Batch Variation in Conjugated Polymers for Organic Electrochemical Transistors

Polymer electronics have attracted extensive attention due to their intrinsic flexibility, structural modifiability, and cost-effective fabrication. However, compared to silicon electronics, polymer semiconductors suffer from their inherent polydispersity, resulting in variations between batches, which becomes a crucial challenge in polymer-based electronics and hinders their large-scale applications. In this study, the focus is on polymers that are significantly affected by batch variations and molecular weight effects in organic electrochemical transistors (OECTs). By introducing channel confinement effect, specifically by reducing the channel length (L) in vertical OECTs, molecular bridges are formed, leading to excellent immunity to molecular weight variation and remarkably enhanced device performance. OECTs based on n-type poly(benzimidazobenzophenanthroline) (BBL) and p-type poly[2,6-(4,4-bis-potassium butanylsulfonate-4H-cyclopenta-[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (CPE-K) with varying molecular weights exhibit nearly identical and high transconductance of 75.00 mS for BBL and 120.00 mS for CPE-K, respectively, with an L of 35 nm. This phenomenon is elucidated by high-resolution transmission electron microscopy and geometry optimization. Furthermore, organic complementary inverters exhibit consistent and stable voltage gain of 60.00 V V^-1 across BBL with different molecular weights and have been successfully used to amplify multiple types of physiological electrical signals. This strategy is expected to accelerate the large-scale production of polymer electronics.