The Application Of Polyoxometalates In Counter Electrodes And Electrolytes On Dye-sensitized Solar Cells

Nowadays, the discordant relationship between rising demand and the descending storage of energy threatens the development of society. Exploring renewable energy resources becomes an urgent affair, especially how to take full advantage of solar energy. Hence, a large number of studies have been concentrated on solar cells in succession. Among the numerous solar cells, Dye-sensitized solar cell(DSSC) have attracted extensive attentions since it was fabricated in 1991 since its low cost and facile fabrication. A DSSC is typically fabricated by three parts: a dye-sensitized photoanode which can absorb visible light and transport electrons,an electrolyte in which complete the regeneration of dye and I-, a counter electrode which can receive electrons catalysis the reduction of I3-. Now researchers around the world focuses on developing alternative materials for dye-sensitised solar cells research, such as looking for new dyes to replace the high cost of pyridine ruthenium dye; looking for stable, high efficiency, and no corrosive electron-transfer mediators; and looking for cheap and good catalytic-property counter electrode materials.This paper mainly discusses the application of polyoxometallate in dye-sensitised solar cells electrolyte and counter electrode.1. Polyoxometalate supported complexes as effective electron-transfer mediators in dye-sensitized solar cells. In this paper, we attempt to introduce two Anderson-type heteropolyanion-supported copper phenanthroline complexes into DSSC electrolyte as the redox shuttles for achieving high solar energy conversion in DSSC. It is confirmed that the introduction of POM into [Cu(phen)2]2+/+shifts the redox potential of Cu(I/II) to the positive direction, restrains electron–hole recombination, facilitates electrons transfer from[Cu(phen)2]+to the dyevia cyclic voltammetry and open-circuit voltage decay measurement.2. Employing polyoxometalates as pure-inorganic electron-transfer mediators on dye-sensitized solar cells. The electrolyte, as a hinge between two conductive transparent electrodes, provides internal electric conductivity, thus it plays one of crucial roles in determining the cell performance. The iodide/triiodide redox shuttle is a widely used electron-transfer mediator working in electrolytes of DSSCs, However, I-/I3- system has some disadvantages, such as the absorption of visible light at high concentration, the corrosiveness towards the Pt cathode and sealing materials, the leakage from the cell due to the high vapor pressure of I2, and the relatively high overpotential for dye regeneration. In this paper, we attempt to employ two Keggin-type POMs K6 Co IIW12O40 and K5 Co IIIW12O40 into DSSC electrolytes as a redox couple and obtained relatively high open circuit voltage(Voc) and fill factors(FF).3. Electropolymerization polyoxometalate(POM)-doped PEDOT film electrodes(denoted as Si W11-PEDOT) and its application in dye sensitized solar cells. Pt electrode has been widely used as the CEs of DSSCs since its high electrocatalytic activity for the conversion of I3-back to I-in the electrolyte and high conductivity. However, Pt electrode has some disadvantages, not only its high cost, which limits its wide application and industrialization, but also the thermal treatment for the synthesis of conventional Pt electrode,which limits the application of plastic substrates in DSSCs. Herein, we design and fabricate a new type of POM(K8[Si W11O39]·13H2O)-doped PEDOT hybrid film via electropolymerization. The electrocatalytic activity for I3- reduction of as-prepared Si W11-PEDOT hybrid film is confirmed to be comparable with platinum via cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), and Tafel polarization. DSSC based on this new type of hybrid film electrode exhibits high conversion efficiency which are comparable with the DSSCs based on Pt counter electrodes.