The Preparetion Of Highly Dispersed Composite Materials Modified By Polyoxometalates Nanocrystals And Its Application In Photovoltaic Devices

In order to reduce the excessive exploitation and use of fossil energy,the task of developing new sustainable energy sources is imminent.Solar energy has attracted widespread attention due to its richness and environmental protection.Dye-sensitized solar cells?DSSCs?as an important component of the third-generation solar cells have their own unique advantages compared to other types of solar cells,such as low material prices,simple manufacturing processes and so on.However,they have not been widely used in photovolitaic field.Improving the photoelectric conversion efficiency of DSSCs has become an urgent problem for researchers.The effective suppression of electron-hole recombinations is a major challenge to improve the performance of DSSCs.Moreover,the preparation of photoanodes with excellent performance is a good method to suppress electron-hole recombinations.Polyoxometalates?POMs?possess good ability to transport and store electrons,which make them occupy important positions in photovoltaic filed.In this work,we explored a new strategy to suppress the electron-hole recombinations in DSSCs by changing the morphology of POMs nanoparticles,increasing the dye loading of photoanodes,and thus improving the photoelectric conversion efficiency of DSSCs.The specific work is as follows:1.Three kinds of POMs nanoparticles with different morphologies were prepared by changing the temperature of hydrothermal conditions,which were hollow rhombic dodecahedral nanocrystals?PW12-H?,rhombic dodecahedral nanocrystals?PW12-R?and SiW9Co3 with a size of about 15 nm.Then those samples were characterized by N2adsorption-desorption isotherm,X-ray photoelectron spectroscopy,transmission electron microscopy and scanning electron microscopy.The results showed that the improved morphologies with well-defined nanostructures have the features of large surface area than powder,which is helpful to prevent the aggregation of POMs and promote the exposure of more active sites.Subsequently,the POMs nanoparticles and TiO2 were composited by sol-gel method.In the process of compositing hollow structure POMs and TiO2,TiO2particles grew in situ in the interior and surface of the hollow structures,so that they could achieve perfect combinations to a greater extent.2.The photovoltaic performance of the DSSCs based composite nanomaterials as prepared is systematically investigated.The photoelectric conversion efficiencies of PW₁₂-R@TiO₂/DSSCs,PW₁₂-H@TiO₂/DSSCs and SiW₉Co₃@TiO₂/DSSCs were 7.28%,8.06%and 7.76%,respectively.PW12-H@TiO2/DSSCs had the highest PCE in this study and was 34%higher than TiO2/DSSCs?6.01%?.This is mainly due to the high dispersion of composite materials that expose more active sites of POMs,effectively accelerate electron transport and extend electron lifetime.In summary,we have explored a new strategy to design low-cost,high-efficiency photoanode materials using POMs nanomaterials with different morphologies to suppress the electron-hole recombinations in DSSCs and achieve a significant increase in photoelectric conversion efficiency.