Modification Of Magnetic Nanomaterials And Its Effect On Agarose-based Dye-sensitized Solar Cells

Abstract:Vigorous development of solar cell technology is an effective way to solve the world’s energy crisis. Dye-sensitized solar cell (DSSCs) is a low cost, simple preparation process and environmentally friendly solar cell, has become a new hotspot as its considerable photoelectric efficiency in recent years. Using Agarose as matrix in quasi-solid electrolyte dye-sensitized solar cell can improve the conductivity of electrolyte and photovoltaic efficiency of DSSCs upgrade. In this thesis, we optimized the performance of agarose-based dye-sensitized solar cells with the following four aspects:1. The effect of PEG2oo content on electrochemical properties of Fe3O4modified magnetic polymer electrolyte:With the increase of PEG200concentration, the dispersion of nano-Fe3O4particles in polymer electrolyte was improved, the ionic conductivity of electrolyte followed a trend as increase-decrease, the maximum ionic conductivity value of2.88×10-3S cm-1occured at PEG200content61.8wt%. Adding excess PEG200would break the structure of agarose polymer, so that the ionic conductivity of the electrolyte reduced. The electronic lifetime and combination resisirtance of dye-sensitized solar cells increased with the increasing of PEG2oo concentration, and the maximum values of both were appeared at68.3wt%. We eventually selected68.3wt%as the best PEG200modified concentrations.2. The influence of surfactants on Fe3O4modified magnetic polymer electrolyte for dye-sensitized solar cells:Fourier transform infrared spectroscopy (FTIR) was employed to characterize the interactions between surfactants and magnetic polymer electrolyte. TW-80and PEG200modified electrolyte showed smooth surface which indicated better dispersion of Fe3O4nanoparticles according to SEM analysis. Through electrochemical impedance spectroscopy (EIS) study, the ionic conductivity, charge transfer resistance, charge recombination resistance and electron lifetime of polymer electrolytes were all improved by modification of surfactants. TW-80modified electrolyte reached the highest ionic conductivity of2.98×10-3S cm-1. Moreover, the photoelectric properties of DSSCs were also significantly enhanced and the best energy conversion efficiency achieved1.83%with TW-80modification.3. Effects of magnetic field intensity on NiO modified agarose electrolyte for dye-sensitized solar cells:After proper treatment under an external magnetic field, the agarose electrolyte exhibited increased ionic conductivity and better penetration into the mesoporous TiO2photoanode film, which improved the power conversion efficiency of the DSSCs. The highest ionic conductivity was5.01×10-3S cm-1perparing under35mT magnetic field. Electrochemical impedance spectroscopy measurement was also performed to analyze the magnetic field effect on cell performance. Light-to-electric conversion efficiencies of DSSCs at25mT and35mT magnetic field intensities were2.95%and2.94%, respectively. After applying proper magnetic filed intensity, the recombination resistance and redox transport resistance in the devices were also improved.4. Study of CO3O4concentration effect on the photovoltaic performance of DSSCs with agarose magnetic electrolyte with/without magnetic field treatment:The addition of proper content of Co3O4nanoparticles in the electrolyte facilitated salt dissociation and improved the concentration of free charges in electrolyte, resulting in increased ionic conductivity, current density and photoelectric efficiency of DSSCs. The optimal CO3O4concentration in polymer electrolyte was3wt%. After the treatment of magnetic field, both the ionic conductivity and penetration ability of the electrolyte were increased, but the charge transfer resistance on Pt/electrolyte interface is increased at the same time. The optimal CO3O4concentration under magnetic field is also3wt%. At this concentration, the efficiency of DSSC under35mT magnetic field treatment was1.72%, which is btter than that of device without magnetic field treatment (1.44%).