| Summary: | 碩士 === 國立清華大學 === 工程與系統科學系 === 102 === Since the dye-sensitized solar cell (DSSC) was reported in 1991 by M. Gratzel ,it has aroused intense interest owing to its low cost, simple preparation procedure, and more environment-friendly compared with traditional photovoltaic devices. Therefore, DSSCs have been considered one of the promising alternatives to conventional solar cells. But the leakage of the liquid electrolyte is the major problem which blocks the application of the flexible device. To solve this problem, the quasi-solid and solid type electrolyte is discovered to replace the liquid one. However, their ion conductivity and ion diffusion ability are limited by the higher viscosity so the cell performance of this type is lower than liquid type.
In this experiment, we added different ratio carbon materials (CM) into the organic solvent (MPN,NMP) as liquid type electrolyte by ultrasonic the CM in the electrolyte solution several hours. At first, we measured its ion conductivity by the AC impedance and then we use Cyclic voltammeter (CV) measurement to survey the influence of the diffusion ability changed by the CM added. The charge transfer resistance of Pt/electrolyte and Nernst diffusion in the electrolyte presents the catalytic ability of CE and diffusion ability of redox couple, and diffusion limited current is confirmed the triiode in electrolyte diffusion ability in different carbon materials ratio. We discovered that added CM can improve the ion conductivity and diffusion ability. Next, to identify the performance of cell, we measured the cell efficiency under illumination of AM1.5 (100mW/cm2). The conversion efficiency is also raised when we added the CM into the electrolyte. Because of that we infer adding carbon materials providing an extended electron transfer material facilitates electron transfer from counter electrode to tri-iodide ions to increase the exchange reaction of redox couple in the viscous electrolyte so that the performance of the cell also be improved.
At last we induce the polymer material into the system to form quasi-solid type electrolyte. We added 10wt% Polyvinyl butyral (PVB) into the NMP system, and 20 wt % Polyethylene Glycol into the MPN system. The ionic conductivity and the diffusion ability are measured after the different CM ratio added. We discovered that the resistance of the quasi-solid electrolyte is lowered and the diffusion ability is also raised due to CM added. In the efficiency rest, the performance of the quasi-solid electrolyte with CM is about 88% of the liquid type one. It can approve the fact that the quasi-solid type solar cells can achieve the high efficiency by CM added into the system which supplies DSSC a opportunity to apply in the flexible device.
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