Electrical Properties of Nickel Phthalocyanine Thin Films Using Gold and Lead Electrodes

Abstract

The electrical properties of nickel phthalocyanine (Ni Pc) thin film sandwich devices have been investigated using gold and lead electrode combinations. At low forward voltages with gold electrode as positive, the device showed rectification properties, while at higher forward voltages the conduction mechanisms were dominated by space charged limited conduction (SCLC) controlled by a single and an exponential trapping levels at two different ranges of applied voltages. Under the reverse bias a Schottky type of conduction process was identified. From our investigations we found that gold electrode acts as an ohmic contact and lead electrodes as a blocking contact to Ni Pc layer with the existence of a barrier region at the lead electrode side of the Ni Pc layer. The effect of oxygen doping on the electrical conductivity of these devices have also been studied. After exposure to dry air for 30 days the device showed a higher order of current both in the forward and reverse bias. In the oxygen doped sample an increase in the rectification ratio and an enhanced value of trap concentrations were observed.