Enhancing the Response Speed of Organic Electrochemical Transistors via Ion Liquid/Metal–Organic Framework-Embedded Semiconducting Polymers

Organic electrochemical transistors (OECTs) are recognized for their ability to combine electronic and ionic transport in the channel, resulting in improved transconductance and reduced operation voltage compared to organic field-effect transistors (OFETs). Nevertheless, the hydrophobic nature of conjugated polymers remains a hindrance to ion drift, thereby causing slow switching speed and limiting their practical application. This study introduces the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]) adsorbed in a metal–organic framework (MOF-525) as an ion reservoir within a conjugated polymer, for the first time, to serve as the active channel in OECTs. Due to shortened ionic drift time, in the poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT-C14) system, the original polymer membrane without MOF-525/[EMIM][TFSI] exhibits a characteristic ON time (τ_ON) of 28.75 s, whereas the PBTTT-C14/MOF-525/[EMIM][TFSI] composite film significantly reduces the τ_ON to 2.56 s with ON/OFF current ratio of 10². Enhancing response speed through facile physical blending of MOF-525/[EMIM][TFSI] in conjugated polymer film can also be realized on flexible substrate and in poly(3-hexylthiophene-2,5-diyl) (P3HT) system which provide a general strategy to broaden the selection of conjugated polymers in accumulation mode OECTs.