Correlating ionic liquid gated organic field-effect transistors electronic performances to electrolytes size and pairing

Alkyl-methylimidazolium based ionic liquids are proposed as gating electrolytes in field-effect transistors and the ionic properties are seen to influence the devices electrical performance. Specifically, over a selection of different cations and anions correlations have been established between the ion-pairing occurring in the pure ionic-liquid and the intensity of the current circulating in the transistor channel in the on state. Ion-pairing was determined by means of pulse-gradient-spin-echo (PGSE) NMR experiments. Moreover, the effect of the ions chemical structure and hydrophobicity on the off-current and on the field-effect mobility as well as on the threshold voltage, are discussed. The occurrence of hysteresis in the current–voltage transfer curves is evaluated and associated to the electrolyte molar conductivity and the ions self-diffusion coefficients. The gained understanding allows to optimize the system reaching better device performance level. Moreover, thanks to the well-known bio-compatibility of this class of ionic liquids, application in electrolyte gated biosensors can be foreseen.