Due to their low working voltages, biocompatibility and high sensitivity, Organic electrochemical transistors (OECTs) have emerged as a transformative technology at the intersection of organic electronics and biology.[1] However, the long-term safety, stability and performance of OECTs are strongly governed by the nature of ionic species involved in electrochemical doping. In this study, we investigated the performance of OECT based on the semicrystalline polymeric semiconductor poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT), using phosphate-based dopant anions as biocompatible alternatives (Fig. 1). Specifically, we evaluated the electrochemical doping behavior of phenyl phosphate (PhPhos) and diphenyl phosphate (Ph₂Phos). Both anions enable effective electrochemical doping, and high OECT performance. In addition, steady-state current measurements show that Ph2Phos dopant sustains high steady-state current at higher gate voltages, indicating a significantly expanded operating window (Fig. 2). These results highlight that tuning the size or chemical properties of the dopant anion is a crucial pathway for enhancing the operational stability of biocompatible OECTs.

1. L. Bai, C. G. Elósegui, W. Li, P. Yu, J. Fei, L. Mao, Front. Chem. 7, 313(2019) DOI: /10.3389/fchem.2019.00313