Characterization of electrodeposited zinc oxide/tetrasulphonatedcopper phthalocyanines (ZnO/Ts-CuPc) hybrid films and their photoelectrochemical properties

Abstract

Hybrid films of zinc oxide (ZnO) and tetrasulphonatedcopper phthalocyanine (Ts-CuPc) have been prepared by cathodic electro-deposition from aqueous O2-saturated solutions of ZnCl2 and Ts-CuPc. The Ts-CuPc content of the films can be varied in a wide range by variation of dye concentration in the electro-deposition bath – from single Ts-CuPc molecules embedded in compact crystalline ZnO to films based on an amorphous Ts-CuPc framework. With increasing dye content the colour of the films changes from light blue to deep blue. All films were characterized by XRD, SEM and AFM. Photoelectro-chemical characteristics of the electrodes were studied by photocurrent spectra and by time-resolved photocurrent measurements in 0.1 M KCl electrolyte. At the same time, changes in the electrical and photoelectrical properties of the films are observed, enabling the tuning of these properties in view of optoelectronic applications. Theoretical calculations based on density functional theory (DFT) models were made to understand the optoelectronic properties of the hybrid films. Different parallel and perpendicular orientations were tested. For the most stable hybrid structure, total and projected densities of states of the system were obtained and the alignment of the levels observed.