Rapid improvements in charge carrier mobility at ionic liquid/pentacene single crystal interfaces by self-cleaning

We report the rapid improvement in the carrier mobility of the electric double layer field-effect transistor based on the ionic liquid (IL)/pentacene single crystal interface. Generally, the surface oxidation of the pentacene single crystal is unavoidable, and the considerable degradation restricts the performance of the field-effect transistor. However, the formation of the IL/pentacene single crystal interface resolves this problem by increasing the carrier mobility by approximately twice the initial value within a few hours. Furthermore, frequency-modulation atomic force microscopy revealed that the aforementioned rapid improvement is attributed to the appearance of a clean and flat surface of the pentacene single crystal via the defect-induced spontaneous dissolution of pentacene molecules into the IL. The field-effect mobility increases with time for a few hours because of the spontaneous dissolution of the defect sites.