Solid-State Ionic Liquid Additive Enhances Mobility in Conjugated Polymer Field-Effect Transistors

Electronic devices based on organic semiconductors are in great demand. However, they are limited by their performance and stability compared to their inorganic counterparts. Accordingly, chemical additives, which improve the electrical and morphological properties of organic semiconductors, have been intensively utilized to develop high-performance organic field-effect transistors (OFETs). Herein, we report a blend of conjugated polymers (CPs) and solid-state ionic liquid (ss-IL), resulting in a substantial improvement in the crystal packing, energy level alignment, and charge transport in CPs. By exploring three distinctive low-k, high-k, and high-capacitance electrolyte gate dielectric materials, we comprehensively examine the impact of ss-IL additive on the device performances of OFETs. Our optimized polymer electrolyte-gated OFETs with the poly(3-hexylthiophene) (P3HT) and poly[[4,8-bis[5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl]-2,5thiophenediyl-[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo [1,2-c:4,5-c′]dithiophene-1,3-diyl]] (PBDB-T) CPs blend with ss-IL showed boosted hole mobilities exceeding 11 and 9 cm² V^-1 s^-1 compared to pristine CPs showing mobilities of 5 and 2 cm² V^-1 s^-1, respectively, attributed to improved injection properties, better CP crystal orientation, intermolecular interactions of CP:ss-IL, and enhanced charge-carrier density in the transistor channel. Our research emphasizes the importance of ionic liquid molecular additives for CPs in achieving high-performance transistor-based devices and paves the way for next-generation optoelectronic devices.