| Summary: | 碩士 === 國立臺北科技大學 === 有機高分子研究所 === 104 === In this study, we tackled the corrosion and leakage problem of conventional iodine-based liquid electrolyte by developing iodine-free gel electrolytes that were solidified with metal oxide nanoparticles for dye-sensitized solar cells (DSSCs). First, two types of liquid electrolytes, with and without iodine, were prepared to investigate the influence of iodine on the photovoltaic performance of TiO2-based DSSCs. Then, three different types of metal oxide nanoparticles (ZnO, TiO2 and SiO2) were tested as gelling agents for both types of liquid electrolytes, and the photovoltaic performance of resulting DSSCs were investigated.
The results show that removing iodine from the electrolyte markedly reduced the FF value, leading to lower overall conversion efficiency (from 7.37% to 6.94%), despite a small improvement in the short-circuit current density (JSC) brought about by the lower absorbance of the I2-free electrolyte. Of the three types of nanoparticles tested, TiO2 yielded best results. Under simulated full sunlight (AM1.5, 100 mW/cm2) the I2-free quasi-solid state DSSCs solidified with 10 wt% of TiO2 nanoparticles achieved 8.07% power conversion efficiency, a 16% improvement compared with what attained by the quasi-solid state counterpart. The increase in the power conversion efficiency was due to higher JSC and open-circuit voltage (VOC). The former can be attributed to reduced charge-transfer resistance at the TiO2/dye/electrolyte interfaces and the diffusion resistance of the electrolyte, while the enhancement in VOC was due to decreased charge recombination.
Durability studies show that quasi-solid state DSSCs had higher stability than the liquid electrolyte counterparts. Also, the I2-free devices outperformed those contained I2, indicating removing I2 from the electrolyte could improve DSSC stability. The I2-free 10%-TiO2 devices showed excellent at-rest stability, retaining more than 95% of their peak efficiencies after 1000 h of storage at room temperature in darkness. When the cells were exposed to 65% relative humidity at 65 °C, the failure time was determined to be ca. 1200 h, corresponding to a lifetime of 5-6 years at room temperature.
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