Enhancement of photocurrent generation from a series of hybrid nanocomposite self-assembled films of transition element-substituted tungstoborates/hemicyanine

A series of electrostatically self-assembled films have successfully been prepared by alternating adsorption of transition element-monosubstituted tungstoborate anions [BW₁₁M(H₂O)O₃₉]⁷⁻ (BW₁₁M, M = Ni, Cu, Cd) and a bichromophore hemicyanine cation of (E)-1,1′-(hexane-1,6-diyl)bis(4-(4-(dimethylamino)styryl)pyridinium) (H⁶), respectively. The UV–Visible spectra showed that the films were uniformly deposited and H⁶ molecules formed J-aggregations in the films. The (BW₁₁M/H⁶) _n films could generate stable cathodic photocurrents of 0.56–1.32 μA/cm² as irradiated with white light (100 mW/cm², 730 nm > λ > 325 nm) at zero bias voltage versus SCE, and the photocurrent action spectra indicated that the cathodic photocurrents were generated based on charge transfer excitation of the H⁶ in the (BW₁₁M/ H⁶) _n films. The composition and structure of polyoxometalate anion in the films have important influences on photocurrents. Moreover, the effects of layer number of (BW₁₁M/H⁶) _n film, applied potentials, and electron acceptor in the electrolyte on photocurrent generation of the (BW₁₁M/H⁶) _n films have been examined, and photoelectric mechanism is also discussed