應用於染料敏化太陽能電池之二氧化鈦奈米粒、奈米棒及其混摻型薄膜電極的製備與鑑識

Abstract

在本論文中，我們藉由界面活性劑的自組裝法以及水熱法製備高結晶性的二氧化鈦奈米棒，並將其應用在染料敏化太陽能電池中。為了判斷二氧化鈦奈米棒電池的好壞，我們利用溶膠-凝膠法製備出的二氧化鈦奈米粒電池作為對照組。根據場發射掃描式電子顯微鏡以及X射線繞射的結果顯示，二氧化鈦奈米棒是長度為100 nm-200 nm，直徑為20 nm-30 nm的銳鈦礦相晶體。我們利用網版印刷法將二氧化鈦奈米棒漿料印在FTO玻璃上，其工作面積為0.16cm2，並將LiI、I2及TBP（4-tert-butylpridine）溶於乙腈及戊腈的混合溶液（體積比為85：15）中作為電解液，在AM 1.5模擬太陽光（100mW/cm2）照射下進行太陽能電池測試。我們比較了在不同厚度下的奈米棒及奈米粒電池，結果顯示隨著薄膜厚度越厚，奈米棒電池的電流密度仍然持續增加，這表示二氧化鈦奈米棒具有快速的電子傳遞速率以及光散射效應。然而，奈米棒結構之其比表面積遠小於奈米粒，因此，我們嘗試利用不同條件之TiCl4後處理、散射層以及界面層來改善其電流密度，而其光電轉換效率可以由6.5%被提昇至7.8%。 此外，我們也利用奈米粒的高比表面積以及奈米棒之快速電子傳遞速率和散射效應製作了由此兩者奈米結構混合所組成的混摻結構電極，為了找到其最佳組成比例，我們製備了五種不同混摻比例的漿料，其混摻的奈米棒重量比分別為20 wt %(P4R1)、33 wt %(P2R1)、50 wt %(PR)、67 wt %(P1R2)及80 wt %(P1R4)，而在上述電池之中，PR可得到7.9%的最佳效率。

In this thesis, we have attempted to fabricate a dye-sensitized solar cell(DSSC) based on the highly crystalline TiO2 nanorods prepared with the surfactant-assisted hydrothermal method. To estimate the performance of the cell composed of the TiO2 nanorods, a cell composed of TiO2 nanoparticles prepared with sol-gel method was fabricated as a reference. The microstructure measured by FESEM and X-ray diffraction was a pure highly crystalline anatase phase with lengths of 100 nm-200 nm and diameters of 20 nm-30 nm. The performance of nanorod solar cells were compared with pure nanoparticle cells at a series of film thickness. With increase of film thickness, the current density of TiO2 nanorod cells showed a continuous increase in the whole thickness range up to 26 μm, indicating the rapid electron transport rate and the light scattering effect of nanorods. However, the much smaller specific surface area of nanorods than nanoparticles was a major problem. Therefore, we tried to improve the current density by TiCl4 treatment, light-scattering TiO2 layer, and interfacial layer. The overall efficiency of TiO2 nanorods could be improved from 6.5% to 7.8%. We also fabricated a cell based on the composites of TiO2 nanorods and nanoparticles. Five pastes containing mixed TiO2 nanoparticles and nanorods were prepared with nanorods concentration of 20 wt %、33 wt %、50 wt %、67 wt %, and 80 wt %, respectively. Among all the cells we prepared, the best efficiency was 7.9%.