Transport mechanisms and the effects of organic layer thickness on the performance of organic Schottky diodes

Experimental results of static and dynamic characteristics for single-layer hole-only devices based on copper phthalcyanine (CuPc) and pentacene are observed in this article. The contribution to injection currents from electrode has been investigated by varying the thickness of the organic film. From the observation of current density versus bias voltage (J-V) characteristics, it is concluded that the space-charge-limited conductivity is the dominant transport mechanism for the organic Schottky diodes. Accordingly, an increase of the organic layer thickness will increase the trapping energy level. However, even with the thin CuPc film down to 50 nm, the dynamic cut-off frequency of the device is still limited to 150 Hz. Low hole mobility and large active area of the device are responsible for the phenomenon. Dramatic enhancement of cut-off frequency up to 11 kHz can be obtained for the pentacene-based Schottky diodes. (c) 2007 American Vacuum Society.