Organic electrochemical transistors based on a conjugated diketopyrrolopyrrole-dialkoxybithiazole copolymer†

Organic electrochemical transistors (OECTs) are promising for bioelectronics due to their ability to amplify signals by converting ionic signals into electronic signals. The performance of OECTs relies heavily on the interaction between electrolyte ions and organic mixed ionic-electronic conductors (OMIECs). We examined how different aqueous electrolytes affect OECTs based on an ethylene glycol-substituted diketopyrrolopyrrole-dialkoxybithiazole copolymer (PDPP-TEG-2Tz), which is primarily p-type and electrochemically doped with anions. Our findings show that compared to the small, highly hydrated chloride anion (Cl⁻), the larger hexafluorophosphate (PF₆⁻) and bis(trifluoromethanesulfonyl)imide (TFSI⁻) anions result in a lower threshold voltage and a faster transient response. Cations like Li⁺, Na⁺, and K⁺ have little impact on OECT performance. Additionally, we created a complementary inverter using p-type PDPP-TEG-2Tz with an n-type naphthalene diimide-bithiophene copolymer (PNDI2C8TEG-2T), achieving a maximum voltage gain of 22.6 at a supply voltage of 0.7 V.