Zinc Oxide Nanocrystallite Aggregates as Photoelectrode and Gel Electrolyte Materials for Dye-Sensitized Solar Cells

• Main Authors: Sheng-Kai Sun, 孫聖凱
• Other Authors: 余琬琴
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/awn69w

碩士 === 國立臺北科技大學 === 有機高分子研究所 === 103 === The present study investigated the application of zinc oxide (ZnO) nanocrystallite aggregates to the fabrication of dye-sensitized solar cells (DSSCs) in two different areas: photoanode and quasi-solid state electrolyte. In the first part of the thesis nanocrystallite aggregates were used as a photoanode material. Flower-shaped aggregates were mixed with commercial ZnO nanoparticles (20-50 nm) in various ratios and fabricated into DSSC photoanodes (on FTO glass substrate) using a low temperature heat treatment (150 °C) process. The effects of aggregate/nanoparticle ratio on the photovoltaic performance of resulting DSSCs were investigated. The flower-like nanocrystallite aggregates were assembled from ZnO nanocrystals (approximately 20-50 nm in size) and had an overall dimension of approximately 400-600 nm. Therefore, the flower-shaped aggregates have both a high surface area for dye adsorption and excellent light-scattering ability to enhance optical absorption. Mixing the aggregates with the nanoparticles can reduce the voids between the aggregates and may lead to better device performance. Experimental results show that the optimum ratio of aggregate was 30 wt%, and a power conversion efficiency of 4.04% was achieved under 100 mW/cm2 simulated light. The other pertinent photovoltaic properties were JSC = 9.59 mA/cm2, VOC = 0.61 V, FF = 0.68. Compared to those fabricated with 100% nanoparticles or 100% aggregates, the DSSCs containing 30 wt% of aggregate in the photoanode had a 30-36% improvement in the power conversion efficiency. In the second part of the thesis, ZnO nanocrystallite aggregates were adopted as a gelling agent. Olive-shaped aggregates and commercial ZnO nanoparticles (20-50 nm) were mixed with a liquid electrolyte in various ratios to form semi-solid electrolytes. The effects of aggregate/nanoparticle and solid/liquid ratios on the photovoltaic performance of resulting DSSCs were investigated. The optimal aggregate/nanoparticle and solid/liquid ratios were determined to be 1:1 and 0.3:1, respectively. With a ZnO photoanode lacking a scattering layer, a power conversion efficiency of 4.41% was attained under 100 mW/cm2 simulated light using the optimized quasi-solid state electrolyte, and the pertinent photovoltaic properties were JSC = 10.17 mA / cm2 , VOC = 0.65 V, and FF = 0.67. On the other hand, the DSSCs based on the liquid electrolyte only reached a power conversion efficiency of 3.11%, with the following photovoltaic properties: JSC = 7.88 mA / cm2, VOC = 0.60 V, and FF = 0.66. The power conversion efficiency of the quasi-solid state cells were 42% higher than that of the liquid electrolyte counterparts, due to significant increases in the JSC and VOC values.