Study On Electrode Interfacial Characteristics Of Dye-sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have attracted wide researchers’ attraction dueto its low cost and easy fabrication and relatively moderate efficiency. but there is stilla great distance away from industrialization because of their cost, efficiency andlong-term stability. In order to improve the performance and reduce manufacturingcosts of DSSCs, two aspects of work were carried out. On one hand, the interfacecharacteristics of DSSCs were investigated using electrochemical impedancespectroscopy (EIS). On the other hand, some natural dyes were chosen to sensitize thecells and the performances of DSSCs were discussed. In general, this paper includesthe following contents:(1) I-V curves and EIS of DSSCs with different PEG content, setting time andlight intensity were tested. The results showed that the cell’s impedance was thesmallest but current density and photoelectric conversion efficiency was the largestwhen PEG content was equal to10%of TiO2. Short circuit current of the cell isincreased with light intensity increasing. The photoelectric performance is decreasedwith setting time increasing, The impedance spectra showed that Rk RPtand Rwaredecreased with light intensity increasing.(2) The surface of TiO2films were modified by using Cr(NO3)3, Sr(NO3)2,La(NO3)3, Ce(NO3)3, Co(NO3)2and Mg(NO3)2solution. The results showed that somecoating layers with large size particles are kept in the surface of TiO2film aftersintered. Coating layers make the total surface area of electrodes increase whichincreases the dye adsorption and improves the photoelectric conversion efficiency ofthe cells. EIS test results showed that the interface resistance of modified electrode ishigher than that of unmodified electrode.(3) Three kinds of electrolyte were prepared according to I-concentration andthey were assembled to cells. The EIS curves of DSSCs were measured. Theexperimental results showed that the effect of electrolyte on Rkand C is evident. Rkand C varies with an external bias according to exponential law. Three-electrode andtwo-electrode testing method were used to measure EIS curves of cell in the sameelectrolyte. The fitting results showed that the interface resistance and diffusionresistance of three-electrode cell is less than the two-electrode cell.(4) Three natural dyes were extracted from pitaya pericarp, xinlimei radish andpurple cabbage with water, leaf of holly, a fruit of radix ophiopogonics, mangosteenpeel, leaf of camphortree and a fruit of camphortree were extracted with ethanol. UV-vis absorption spectra of those natural dyes and I-V curves of DSSCs sensitizedby these natural dyes were also measured.