The Preparation Of Nanosized Polyoxometalate Material And Its Application In Photovoltaic Devices

A severe problem of modern societies is the increasing emission of greenhouse gases produced by utilizing fossil fuel as the primary source of energy,with conflicting views on how to replace both petroleum and coal with renewable harmless energies.One possible solution is to take advantage of inexhaustible solar power via new type solar cells working to accomplish energy conversion.Dye-sensitized solar cells（DSSCs）have attracted more attention than other new type solar cells because of their simple fabrication process,low production costs,relatively high photoelectric conversion efficiency（PCE）and environmental safety.Polyoxometalate（POM）has already been confirmed to act as an effective electron-transfer mediator for improving the PCE of DSSCs based on our studies.However,it may be limited by the agglomeration of the polyoxoanions.Therefore,we improve our previous synthesis strategy via breaking the Metal-organic frameworks with POMs as the secondarybuildingunits([Ni（bpp）（H₂O）₂]₃[P₂W₁₈O₆₂]·24H₂O（1）and H₆[Cu₃（H₂O）₆(P₂W₁₈O₆₂)₂（3-dpye）₆]·28H₂O（2）)to design and synthesize small-size and high-dispersive POM nanoparticles by means of compositing with TiO₂ via the calcination to remove the organic ligand.We ultimately obtain two kinds of composites P₂W₁₈·NiO@TiO₂and P₂W₁₈·CuO@TiO₂ with small-size and high-dispersive P₂W₁₈O₆₂^6-(denoted as P₂W₁₈)nanoparticles,respectively.Moreover,the characterization and photoanodes properties of the composite are investigated.TEM and element mapping confirm that P₂W₁₈ nanoparticles with the diameter of¹ nm are uniformly distributed in TiO₂ composites.The loading amount（wt%）of POM in MOFs achieves 75.67%.The small-size and high-dispersive P₂W₁₈nanoparticles may provide more active sites and specific surface areas for improving the PCE of DSSCs.Finally,the investigations indicate that the PCE（N719）of composite P₂W₁₈·NiO@TiO₂ and P₂W₁₈·CuO@TiO₂ photoanodes rise to 7.56%and7.37%,which were26%and 23%higher than the pristine TiO₂ based photoanodes,respectively.