Preparation, Characterization, and Photoelectric Properties of an Electrostatically Self-Assembled Film Based on Tungstophosphoric Acid and a Binuclear Ru(II) Complex

An electrostatically self-assembled film based on tungstophosphoric acid (PTA) and a binuclear Ru(II) complex RuL was prepared and characterized by UV-vis absorption spectroscopy and cyclic voltammetry. A linear increase in the UV-vis absorbance with the number of deposited layers indicated that the film deposition was uniform and reproducible. The cyclic voltammogram demonstrated that PTA and the binuclear Ru(II) complex assembled in the film were redox active with surface confined characteristics. The photoelectrochemical properties and mechanism of photocurrent generation have also been studied. A five-layer (PTA/RuL)₅ film on the ITO was found to exhibit a large cathodic photocurrent density of 5.32 μA/cm² while irradiated with polychromatic light (730 nm > λ > 325 nm) at an applied potential of −0.3 V versus saturated calomel electrode. The photocurrent action spectrum was in agreement with metal-to-ligand charge-transfer (MLCT) band of RuL in the absorption spectrum, which indicated that the photocurrent was generated based on MLCT excitation of the RuL in the film. It is noteworthy that the incident monochromatic photon-to-current conversion efficiency was calculated to be 1.1% at a wavelength of 450 nm.