在我們的研究中，我們率先將介孔洞(mesoporous)二氧化鈦球珠(TiO2 bead)引入低溫可撓式染料敏化太陽能電池(flexible dye-sensitized solar cell)中。二氧化鈦球珠的銳鈦礦(anatase)相和晶粒間方向性鍵結(oriented attachment)的存在，使電子有極快的電子擴散(electron diffusion)速率。此外，具次微米大小的二氧化鈦球珠導致優越的光散射(light scattering)效應。結合上述兩項優點，二氧化鈦球珠被期望用來得到高效率的染料敏化太陽能電池。在我們的努力下，成功得到約5%或超過5%的效率，分別藉由二氧化鈦球珠做為完整的光電極或散射層。與商業用粉末P25來做為比較，P25電池的最佳效率僅達4.3%。
本研究分為兩部分，一為二氧化鈦球珠的特性分析，另一為其應用於可撓式染料敏化太陽能電池，第一部分連結製程參數與二氧化鈦球珠的特性。我們使用新穎的二階段法來製備二氧化鈦球珠，包括溶膠凝膠(sol-gel)法及水熱(hydrothermal)法。在第一階段調整六甲基四胺的含量，在第二階段則調整水熱溫度，以獲得不同結晶性、表面氧空缺濃度及球珠尺寸。我們使用多種分析來評估可撓式染料敏化太陽能電池，包括電化學分析及光學分析。我們率先證實球珠尺寸對電池表現有顯著的影響，尤其是對光收集及電子注入效率。此外，我們證實二氧化鈦球珠的品質像是結晶度及表面氧空缺濃度，會影響電子擴散及存活時間，故得到不同的載子收集效率。因此我們建議使用500奈米尺寸、結晶性佳及氧空缺濃度低的二氧化鈦球珠做為光電極。750奈米的二氧化鈦球珠擁有較多的背向散射，適合做為散射層。總而言之，我們連結各項分析，並且提供獨特的見解以指出嶄新的方向，使添加新穎介孔洞二氧化鈦球珠的可撓式染料敏化電池未來能獲得極高的效率。

In our research, we firstly introduced mesoporous TiO2 beads into low temperature flexible dye-sensitized solar cells (FDSCs). The pure anatase phase of TiO2 beads and the existence of oriented attachment between grains in TiO2 beads enable the ultra-fast electron diffusion rates. Additionally, TiO2 beads with submicron-meter sizes cause excellent light scattering effects. Combining with these two advantages, the high efficiencies are expected by the use of TiO2 beads in DSCs. In our efforts, we successfully obtained the high cell efficiencies around or over 5% by using TiO2 beads as the whole photoanode or scattering layer, respectively. Comparing with commerial P25 powders, the optimum cell efficiency of P25 cell is 4.3%.
This study mainly divided into two parts, one is the characterization for TiO2 beads, another is its applications in FDSCs. The fisrt part correlates preparation parameters with the characteristic of TiO2 beads. We use a novel two-step method to prepare TiO2 beads involving sol-gel process and hydrothermal method. By adjusting the amount of hexamine in fisrt step and the hydrothermal temperature in second step, the TiO2 beads with various crystallinities, suface oxygen vacancy concentrations and sizes are obtained. We used every kind of analyses to evaluate the FDSCs including electrochemical and optical analysis. We fisrtly demonstrated that the sizes of TiO2 beads strongly affect the cell performances, especially for light-harvesting efficiency and electron-injection efficiency. Moreover, we demonstrated that the quality of TiO2 beads like crystallinity and surface oxygen vacancy concentrations affect the electron diffusion time and electon lifetime, resulting in different charge-collection efficiency. Therefore, we suggested that the use of TiO2 beads with 500 nm-sized, better crystallinity and less oxygen vacancies is more proper for photoanodes. The 750 nm-sized TiO2 beads having more back scattering is suitable for use as the scattering layer. To sum up, we correlated various analyses and provided distinctive understanding to indicate a brand-new direction to reach ultrahigh efficiency for FDSCs by using the novel mesoporous TiO2 beads.

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