Study On The Quasi-semiconducting Properties Of Polyoxometalates And Influencing Phthalocyanine Dye-sensitized Solar Cells Anode

In the21st century，energy and environment are two major issues which we must solve.The utilization of solar energy has received more and more attention in recent years. As aresearch field, improving the photoelectric conversion efficiency of semiconductor materialsis widely studied. Polyoxometalates (POMs), a well-known class of nanoclusters that havesimilar properties to semiconductor metal oxide, are a kind of good electron acceptors withremarkable structural diversity. They have the ability to promote electron transfer rate of thesemiconductor conduction band by trapping photogenerated electrons, and then improves thephotovoltaic response. In this paper, we focused on the semiconductor properties ofKeggin-type polyoxometalates. We also prepared a series of POMs/semiconductors compositefilms and investigated their photovoltaic performances.1. We synthesized Keggin-type polyoxometalates (PW12,SiW12, BW12, H2W12, CoW12andGeW12) and systematically studied on their quasi-semiconducting for the first time. The bandgap, HOMO, LUMO and the surface information of POMs are characterized by diffusereflectance UV-vis spectra, cyclic voltammetry and surface photovoltage spectra. Photocatalytic degradation of methyl orange (MO) was studied in this paper. The resultsobtained from this study can further serve as a guide for applications of POMs inphotocatalysis, solar photovoltaic cells, and water splitting devices.2. We prepared the POMs(PW12, SiW12, BW12, H2W12, CoW12and GeW12)/TiO2compositefilms by doctor blade technique. We study on the photoelectrochemical performance, theelectron transport and electron–hole recombination of these POMs in TiO2film bymeasurements of I–V curves, photocurrent responses and electrochemical impedancespectroscopy (EIS). EIS measurements proved that introducing POMs into TiO2film couldreduce electron-hole recombination and facilitate photogenerated electron transfer, whichenhanced the light-to-electricity conversion efficiency.3. We fabricated the phthalocyanine dye-sensitized solar cells (DSSCs) based on both the onlyTiO2photoanode and the PW12/TiO2photoanode. Compared to the TiO2photoanode, thepower conversion efficiency of PW12/TiO2photoanode was improved.The reasons were asfollows:(1) the PW12/TiO2composite film could adsord more phthalocyanine dye than onlyTiO2film;(2) The incorporating of PW12into TiO2photoanode could reduce electron-holerecombination and improve electron transfer.