Enhanced photovoltaic response by incorporating polyoxometalate into a phthalocyanine-sensitized electrode

A photovoltaic electrode material consisting of cobalt tetraaminophthalocyanine (CoTAPc) and Dawson-type phosphomolybdate (P2Mo18) was fabricated through the layer-by-layer (LbL) assembly method. The film electrode was characterized by UV-vis spectroscopy, IR spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and photoelectrochemical measurements. Photovoltaic measurement of the film electrode under light irradiation of 365 nm demonstrated that the P2Mo18/CoTAPc composite film electrode exhibits higher photocurrent and power conversion efficiency (eta) than the phthalocyanine-only electrode, furthermore the increased photocurrent of (P2Mo18/CoTAPc/PSS/PAH)(5) is not equal to the direct photoresponse addition of P2Mo18 and CoTAPc. Based on the results of fluorescence quenching measurements, the enhanced photovoltaic effect should be attributed to the occurrence of the photoinduced electron transfer between CoTAPc and POM, which increases the efficient dissociation of excited electron-hole pairs (excitons). The present research represents the first example of enhancing the photovoltaic response of organic photovoltaic materials by the assistance of polyoxometalates.