應用於染料敏化太陽能電池之不同均一粒徑二氧化鈦奈米球形結構的製備與鑑識

Abstract

在本論文中，利用四氯化鈦水溶液做為前驅物成功開發出一低溫非水熱合成奈米二氧化鈦球形結構的方法。藉由調控六水合氯化鎂或乙二醇對鈦前驅物的莫耳比例可製成一系列不同粒徑的奈米二氧化鈦球形結構，再利用X射線繞射以及場發射掃描式顯微鏡來鑑識，得知此奈米二氧化鈦球形結構為金紅石相，並且具有300奈米至1微米以上的不同尺寸。結果發現添加六水合氯化鎂對於控制奈米二氧化鈦球形結構粒徑的能力較差，乙二醇則具有較佳的控制能力，並且提出此兩種方法對於控制奈米二氧化鈦球形結構的生長機制。最後調控乙二醇比例能夠有效地合成一系列粒徑均一的二氧化鈦奈米球形結構，其尺寸分別為700±50 nm (EG5)、600±50 nm (EG10)、500±50 nm (EG15)、350±50 nm (EG20)、250±50 nm (EG25)，並將上述的不同粒徑球形結構應用於染敏太陽電池中做為散射層，討論不同粒徑的球形結構做為散射層對原件效能的影響。 結果發現，隨著球形結構的粒徑下降，會使比表面積增加、染料吸附能力增強，而EG25為上述一系列球形結構中具有最高的比表面積以及染料吸附能力者，但是由於EG25的粒徑最小而導致EG25的穿透率高、反射率低，此結果顯示EG25散射能力較差，因此EG25對於散射層應用上的表現較其他EG結構差。在AM 1.5模擬太陽光(100 mW cm-2)照射下進行太陽能電池效率的量測，結果顯示EG20奈米球形結構可以和SOLARONIX公司生產的散射層漿料Ti-Nanoxide R/SP有相當的原件效率，目前以EG20做為元件散射層最高效率值可達8.75%。

In this thesis, by utilizing titanium tetrachloride as precursor in water-based solution, we successfully developed a new non-hydrothermal method to fabricate monodispersed TiO2 nanosphere. By adjusting the molar ratio of magnesium chloride hexahydrate or ethylene glycol relative to the titanium precursor, a series of different size TiO2 nanospheres were produced. The structure of the nanospheres was characterized by X-ray diffraction and FESEM. The phase was identified to be rutile and the size was found to be in the range 0.3~1 μm. We found that it was difficult to control the size of TiO2 nanospheres in magnesium chloride hexahydrate solution, but much easier in ethylene glycol solution. We proposed a mechanism to rationalize the discrepancy for the two methods. Finally, by utilizing ethylene glycol, a series of monodispersed TiO2 nanospheres were produced with diameters 700±50 nm (EG5), 600±50 nm (EG10), 500±50 nm (EG15), 350±50 nm (EG20), and 250±50 nm (EG25). Using these TiO2 nanospheres as light-scattering layer in dye-sensitized solar cell, we studied how the size of the TiO2 nanospheres as light-scattering layer affecting the efficiency of a cell. Based on these results, decreasing the size of TiO2 nanospheres could increase surface area and the amount of dye loading. EG25 has the highest surface area and dye loading amount in the series of TiO2 nanospheres. However, because of its smallest size of EG25, the high transmission and low reflection reduces the effect of light-scattering, so EG25 as scattering layer did not show cell performance compared with others. The photovoltaic performance was measured under simulated AM 1.5 sunlight (100 mW cm 2). The result reveals EG20 as light-scattering layer exhibits the best cell performance reaching the power efficiency 8.75%, which is comparable to those made of commercial pastes (Ti-Nanoxide R/SP, SOLARONIX ).