Influence of electrode on electrical conduction of ZincPhthalocyanine (ZnPc) thin films

Abstract

The electrical conduction properties of ZincPhthalocyanine (ZnPc) thin films have been studied using copper, silver and aluminium electrodes. The sandwich structures were prepared by the thermal evaporation method. The I–V characteristics were investigated to identify the dominant charge transport mechanism in the films. Among all possible mechanisms, it was observed that the data fits well to the SCLC type of conduction in the Al/ZnPc/Al and Schottky type of conduction prevails in the Ag/ZnPc/Ag and Cu/ZnPc/Cu devices. The trap levels and its dependence of structure have been studied and results are discussed. The charge transport phenomenon in the ZnPc films seems to depend highly on the electrode material and temperature. The carrier mobility increases with increasing temperature whereas the density of trapped holes decreases with increasing temperature. The barrier height also decreases with increase in temperature. The influence of the temperature on the electrical parameters such as saturation current density (Js), barrier height (Φb), density of states in the valence band edge Nd (m−3), the position of the Fermi level EF (eV), ionized acceptor atom density Ne (m−3), activation energy ΔΦ (eV), mobilities of hole (μ0) and the concentration of free holes in the valence band (n0) have been discussed in detail.