Conjugated Polyelectrolytes for Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) have been demonstrated in a wide range of applications such as analyte detection, neural interfacing, impedance sensing and neuromorphic computing. Majority of OECTs use PEDOT:PSS and liquid electrolytes. In this talk, I will discuss the development of conjugated polyelectrolytes (CPEs) as semiconductors for OECTs. CPEs are materials that comprise a conjugated polymer backbone and charge-functionalized alkyl side chains and counterions. The anionic CPE poly[2,6-(4,4-bis-potassium butanylsulfonate-4H-cyclopenta-[2,1-b;3,4-b’]- dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBTSO3K, or CPE-K) is part of a unique class of organic semiconducting polymers that are soluble in water and become doped in the presence of a proton source. CPE-K are used as mixed conductor materials for OECTs to replace PEDOT:PSS. CPE-based OECTs operate in either the accumulation or depletion mode. We investigate the impact of the alkyl chain lengths and the conjugated backbone on the optical property, the film morphology, the electronic and ionic conductivity and the transconductance in OCETs.