Preparation And Photovoltaic Properties Of Polyoxometalates/Semiconductor Nanocomposite Film

The utilization of the solar energy for insufficiency of current energy resources is a hot and permanent subject. Exploiting photovoltaic functional materials with top performance is the foundation for solar energy conversion. The enhancement of photovoltaic response for semiconductor materials is still one of the research focuses in contemporary materials science. Polyoxometalates （POMs）, a class of nanoclusters with intriguing structures and unexpected physical chemistry properties, hold the capability of electron transfer ,Which makes them suitable for photoelectron acceptor of photovoltaic electrode. In this paper, we focus on the preparation of nanocomposite film containing POMs, phthalocyanine, carbon nanotubes （CNTs） and inorganic semiconductor materials by self-assembly technology. Furthermore, the synergic effect of POMs on photovoltaic activities for the nanocomposite film electrodes were investigated.A photovoltaic electrode material consisting of cobalt tetraaminophthalocyanine （CoTAPc） and Dawson-type phosphomolybdate (P₂Mo₁₈) was fabricated through layer-by-layer （LbL） assembled method. Photovoltaic measurement of the film electrode under UV light irradiation demonstrated that the P₂Mo₁₈/CoTAPc composite film electrode exhibits higher photocurrent and power conversion efficiency （η） than the phthalocyanine-only electrode, furthermore the increased photocurrent of (P₂Mo₁₈/CoTAPc/PSS/PAH)₅ is not the simple photoresponse accumulation of P₂Mo₁₈ and CoTAPc. This should attribute to the occurrence of the photoinduced electrons 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 photovoltaic response of organic photovoltaic materials by the assistance of polyoxometalates.A systematic series of photovoltaic electrodes modified chemically with layer-by-layer （LbL） self-assembled multilayers of Alcian blue （AB）, Carbon nanotubes （CNTs） and Dawson-type phosphomolybdate (P₂Mo₁₈) have been designed to provide valuable insight into their diffirent photovoltaic performance. Photovoltaic responses of these film electrode under UV light irradiation demonstrated that the CNTs/AB composite film electrode showed higher photocurrent and power conversion efficiency （η） than the AB-only electrode, while the P₂Mo₁₈/PAH/ CNTs/AB composite film electrode exhibits the highest photovoltaic response in the series of film electrodes. The differences in photoinduced charge transfer and efficient electron transport by CNTs which increases the efficient dissociation of excited electron–hole pairs （excitons） are suggested to be responsible for the different photovoltaic performances of these film electrodes. This work could have significance not only in the enhancement of photovoltaic response but also in the attempts to tune photovoltaic performances of photoactive electrode by incorporating the chemical materials with different band gap. These results will be helpful to us in developing promising new photovoltaic materials.The effect of POMs on photovoltaic activities for the inorganic semiconductor/organic photovoltaic materials nanocomposite film electrodes were investigated by self-assembly technology. A systematic series of photovoltaic electrodes modified chemically with layer-by-layer （LbL） self-assembled multilayers of phthalocyanine tetrasulfonate （TSPCCu）, Carbon nanotubes （TiO₂） and Dawson-type tungstophosphate (P₂W₁₈) have been designed. Photovoltaic measurement of these film electrodes demonstrated that the inorganic semiconductor/organic photovoltaic materials composite film electrode exhibits higher photovoltaic response than the inorganic semiconductor-only or organic photovoltaic materials -only electrode, while the introduction of POMs further improves the photovoltaic propties of the composite film electrode. The present research demonstrates the example of enhancing photovoltaic response of the inorganic semiconductor/organic photovoltaic composite materials by the assistance of polyoxometalates.New bifunctional nanocomposite films containing water-insolvable cobalt tetraaminophthalocyanine （CoTAPc） and 2:18 tungstophosphate anions (P₂W₁₈) were successfully fabricated using the electrostatic layer-by-layer （LbL） assembled method in nonaqueous media. UV-vis measurements revealed regular film growth with each four-layer {P₂W₁₈/CoPc/PSS/PAH} adsorption. AFM analysis provides the morphology of the multilayer films. The cyclic voltammetric curves indicate that the film shows electrocatalytic activity for chlorate anion.