Trapping of Charge Carriers in Organic Molecular Materials: Phthalocyanine Thin Films Revisited

The technique of temperature-modulated space-charge-limited currents was employed to study the energetic distribution of local states in thin films of metal-free phthalocyanine. Four well-defined local levels were detected within the energy range 0.5-0.3 eV, accompanied by an onset to a manifold of shallower states. The morphology of the films, depending on the deposition rate and changing from polycrystalline to nearly amorphous, affects the densities of local states but not their energies.