Electrochemical characterization of pentacene thin films in vacuum with an ionic liquid as electrolyte

We propose a new method for the basic characterization of organic semiconductor properties: an electrochemical impedance analysis with an ionic liquid in vacuum. As a demonstration, we applied this method to the estimation of the acceptor density for c-axis-oriented pentacene films grown on an indium tin oxide substrate. The behavior in the growth of a depletion layer within pentacene could be well understood using the conventional simple capacitance model, and the acceptor density was successfully estimated from the Mott-Schottky plot, typically giving a value of 3.7 × 10 ¹⁵cm^-3.