Ambipolar Organic Bulk Heterojunction Electrochemical Transistors for High Gain Inverters

Organic electrochemical transistors (OECTs) have significant potential in bioelectronics due to their strong signal amplification, low-voltage operation, and inherent biocompatibility. Complementary inverters, essential for electrophysiological signal amplification, require both p-type and n-type OECTs. Ambipolar OECTs offer advantages in simplifying fabrication and reducing costs. However, achieving balanced ambipolar OECTs remains challenging due to the contradictory molecular design requirements for optimizing both hole and electron transport. This requires sophisticated molecular engineering strategies. In this study, we develop high-performance ambipolar OECTs by blending an n-type glycolated naphthalenediimide (NDI)-dialkoxybithiazole (2Tz) copolymer (P-7O) with a p-type bithiophene-thienothiophene polymer (P(g2T-TT)). The resulting devices exhibit a low threshold voltage of 0.45 V and −0.56 V, exceptional operational stability (over 10 h in water), and switching ratios greater than 103 in both operating modes. These devices enable inverters with high voltage gains (254 V/V at positive bias and 71 V/V at negative bias).