染料敏化太陽能電池之「類固態電解質」有助於發展穩定性高的電池元件，改善液態電解質容易揮發漏液及無法大面積使用等缺點，同時降低固態電解質與電極介面間電阻。本研究以聚二氟乙烯-六氟丙烯共聚高分子（PVDF-HFP）作為高分子基材、二氧化鈦奈米管（Titanium oxide nanotube，TiNT）為填充物，與1-烷基-3-甲基咪唑碘離子液體（RMII）摻合製備高分子類固態氧化還原對電解質。於此種無溶劑高分子奈米複合電解質中，TiNT的存在可幫助提升電荷的傳遞。 PVDF-HFP主鏈與側鏈上的高陰電性氟官能基，可與離子液體的咪唑陽離子（RMI＋）形成配位，使其在兩者之間進行自組裝的排列，形成離子傳導通道，使氧化還原對可在通道內快速傳遞。另一方面，TiNT表面有許多氫氧官能基，其與RMI＋之間的作用力可幫助陽離子在TiNT表面進行排列。TiNT為一具方向性結構的奈米管，離子液體在其表面形成高度排列的結構，而I-與I2即可在這結構間形成高傳導效率的氧化還原對。此種部分排列且具方向性的離子傳導通道，可提升離子的擴散並增加離子的移動性。研究中以電化學方法進行介面電阻的分析，指出電解質中TiNT的存在，會破壞離子液體在電極上形成的Helmholtz層，藉以降低電解質與電極間的介面電阻。因此，在電解質中加入PVDF-HFP與TiNT可顯著提升太陽電池的光電轉換效率。 本研究進一步探討離子液體側鏈具不同官能基及不同碳鏈長度對電解質的影響，發現離子液體具八個碳側鏈（OMII）時，電池元件可達到最好的性能，其中OMII在TiNT表面的自組裝排列最為顯著。當電解質含有PVDF-HFP、TiNT及OMII時，太陽能電池具有最佳光電轉換效率，其光電流密度、開路電壓、填充因子及電池光電轉換效率分別為13.98 mA/cm2、582mV、0.64、4.93 %。 Quasi-solid state dye-sensitized solar cells (DSSCs) were fabricated with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and room temperature ionic liquid (RTIL) as gel polymer electrolyte. The ionic liquids used are 1-alkyl-3-methylimidazolium iodides (RMII) and I2 are dissolved as a redox couple. Because of their wide electrochemical window, non-volatility and thermal stability, the ionic liquids are used to replace the volatile solvents. An improvement in the solvent free system is the addition of titanium oxide nano-tube (TiNT) which forms the composite polymer electrolytes with substantially improved ion conductivity. The polar fluorine groups on PVDF-HFP attract the cation of RMII and provided high degree of ion dissociation. The RMI+ would aggregate on the polymer chain and forms the ionic conducting channel. On the other hand, the surface of TiNT contains numerous oxygen groups which also can attract the RMI+. Since the structure of TiNT is orientated, self assembly of RMI+ with high degree of order is established where I- and I2 forms highly efficient redox couple. The partially ordered and oriented ion conducting channel promotes the ion diffusion and improved the ion mobility. Electrochemical analysis of the interface resistance also indicated the presence of TiNT also reduced the electrode-electrolyte interface resistance by destroying the Helmholtz double layer. As results, the photo-electronic conversion efficiency of the DSSCs was raised by adding the PVDF-HFP and TiNT to the electrolytes. The different effects of the alkyl side chain length of 1-alkyl-3-methylimidazolium iodides (RMII) on the electrochemical behavior and the photo-electronic conversion efficiency are also examined. The best performance is found with octyl side chain (C-8) where the self-assembly behavior on TiNT surface is also found to be the most prominent. On using the composite electrolyte with PVDF-HFP, TiNT and 1-octyl-3-methylimidazolium iodides (OMII), the DSSC exhibits a high energy-conversion efficiency of 4.93% under 100mW cm-2.
