本研究中採用電化學陽極處理方式製備二氧化鈦奈米管,主要以鈦片做為基板製作二氧化鈦奈米管陣列,利用定電流法平均每小時可成長4 μm,再經由不同陽極處理時間獲得不同的奈米管長度,探討二氧化鈦奈米管表面形態,並應用於染料敏化太陽電池(dye-sensitized solar cell; DSSC)之光陽極,研究奈米管長度對於光電轉換效率之影響。使用場發射掃描式電子顯微鏡(FE-SEM)、X光繞射儀(XRD)、紫外與可見光譜(UV / vis)、光電轉換效率及交流阻抗圖譜做分析。可藉由SEM圖分析本實驗經由不同的陽極處理時間可獲得二氧化鈦奈米管長度約分別為10 μm、20 μm及30 μm,且奈米管陣列孔徑平均約為100~110 nm。 XRD圖發現經通氧退火的方式轉變成較好的銳鈦礦晶相,有利於光電轉換效率的增加。透過UV / vis分析不同方法製備白金背電極的穿透率,其中以熱還原法製備白金背電極在可見光光譜範圍的光穿透率約為80 %左右。在不同奈米管管長10 μm、 20 μm、 30 μm製作出的染料敏化太陽能電池,使用太陽光模擬器光功率為AM 1.5 100 mW/cm2中量測,獲得光電轉換效率分別為3.21 %、4.35 %、4.34 %。經過四氯化鈦處理後,在管長為20 μm可獲得最佳效率為6.58 %。同時以交流阻抗分析儀量測做元件之內部阻抗分析,發現電子在結合率會隨著管長越長而變小,顯示奈米管長度越長增加電子傳遞路徑導致再結合率(keff)增加,此外電子生命週期(τeff)也隨著降低,但電子再結合的電荷傳輸阻抗(Rk)則隨著管長越長而變小,管長越長使得染料吸附量增加導致染料激發之電子增多,使得電阻值下降。
In this study, we used the electrochemical anodization to prepare TiO2 nanotubes arrays that were investigated by field emission scanning electron microscopy (FE-SEM), X-ray Diffraction (XRD), UV-visible, I-V characteristics analyses and Electrochemical Impedance Spectroscopy (EIS). In the FE-SEM analysis, the lengths of TiO2 nanotubes arrays prepared by electrochemical anodization used Constant current method using the average growth per hour 4μm, can be obtained with approximately 10 μm, 20 μm and 30 μm. After TiCl4 treatment, the walls of TiO2 nanotubes were coated with TiO2 nanoparticles. XRD patterns can be found that the oxygen annealed TiO2 nanotubes have a better anatase phase. Preparation of counter Pt-electrodes by , transmittance in the visible range of 80 %. The conversion efficiency with different length of TiO2 nanotubes photoelectrodes are 3.21 %, 4.35 %, 4.34 % with 10 μm, 20 μm, 30 μm, respectively. After TiCl4 treatment, the efficiency of TiO2 nanotubes photoelectrode for dye sensitized solar cell can be improved to 6.58 %. In the electrochemical impedance spectroscopy (EIS) analysis, the value of Rk decreases with increasing the thickness of TiO2 thin films, the primary cause is related with the dye adsorptive capacity. It may be due to the stimulation of illumination for the electron in the dye, resulting in the reduced of the Rk.