Enhanced photocurrent generation from an electrostatically self-assembled film of sandwich-type tetracadmium(II) tungstophosphorate/hemicyanine

摘要

A photoelectric conversion film consisting of sandwich-type tetracadmium(II) tungstophosphorate [P_2W_(18)Cd_4(H_2O)_2O_(68)]~(10-) (P_2W_(18)Cd_4) and a bichromophore hemicyanine of (E)-1,1'-(hexane-1,6-diyl)bis(4-((E)-2-(4-(dimethylamino)naphthalen-1-yl)vinyl)pyridinium) bromide (N~6) was prepared by electrostatic self-assembly technique, and characterized by UV-vis spectroscopy, cyclic voltammetry and photoelectrochemistry. The UV-visible spectra showed that the film was uniformly deposited and N~6 molecules formed J-aggregations in the films. The cyclic voltammetry showed that the P_2W_(18)Cd_4 and N~6 in the films were electrochemically active with surface-confined characteristics. As irradiated with white light, the (P_2W_(18)Cd_4/N~6) monolayer film gave stable cathodic photocurrent that is 2.4- and 6.7-fold as great as electrostatically self-assembled monolayer film of (P_2W_(18)Cd_4/H~6) {H~6 =(E)-1,1'-(hexane-1,6-diyl)bis(4-(4-(dimethylamino)styryl)pyridinium) bromide} and Langmuir-Blodgett monolayer film of analogous hemicyanine (E)-4-(2-(4-(dimethylamino)naphthalen-1-yl)vinyl)-1-octadecylpyridinium iodide. The photocurrent action spectrum indicated that the cathodic photocurrent was generated based on charge transfer excitation of the N~6 in the film. The effects of applied bias voltages, electron acceptor, and layer numbers of the (P_2W_(18) Cd_4/N~6)_n films on photocurrent generation of (P_2W_(18)Cd_4/N~6)_n film were examined.