Influence of injection barrier on the determination of charge-carrier mobility in organic light-emitting diodes by impedance spectroscopy

The influence of injection barrier on mobility determination in organic light-emitting diodes (OLEDs) by IS measurements is numerically examined. The theoretical basis of IS measurements for mobility determination is a single injection space-charge-limited current model which assumes Ohmic contacts (no injection barrier). It is found that the mobility of carrier injected from the Schottky contact whose barrier height is less than 0.4 eV can be correctly determined by analyzing the frequency dependence of conductance of OLEDs (mobility can also be determined by analyzing the frequency dependence of capacitance in case where the barrier height is less than 0.2 eV.).