聯吡啶染料在不同酸鹼度水熱法環境處理之二氧化鈦奈米管陣列上的吸附行為與它在染料敏化太陽能電池元件的應用

Abstract

本論文研究主題是經過水熱法處理後的二氧化鈦奈米管。為了預防二氧化鈦奈米管在水熱法處理過程中崩裂破碎，必須使用高於400℃的溫度進行前處理。X光繞射圖譜顯示經過水熱法處理後的二氧化鈦奈米管，維持銳鈦礦的結晶晶相。提高前處理溫度或增加水熱法溶液容量，有增強二氧化鈦奈米管結晶性的效果，對於染料吸附量與太陽能電池元件光電轉換效率，皆有優化的效果。調變水熱法溶液的酸鹼度也是研究重點。綜合元件特性並且根據傅立葉紅外線光譜與X光光電子能譜量測結果，顯示二氧化鈦在較酸或較鹼的溶液中進行水熱法處理之後，表面的Ti-OH和Ti-OH2鍵結數量會增加，而Ti-O-的鍵結數量會減少。此二氧化鈦表面鍵結成份的消長變化，會造成染料吸附量減少，進而使太陽能的吸收轉換效率劣化。 此外，在受過水熱法處理的二氧化鈦奈米管上，分別使用N3與N719，比較兩種染料的吸附特性。一般來說，二氧化鈦奈米管經水熱法處理後，吸附N3染料做為電極所製成的太陽能電池，會得到比使用N719染料更好的光電特性。除了消光係數與染料分子大小的差異之外，N719染料上的TBA離子容易吸附在經過以較酸或較鹼溶液進行水熱法的二氧化鈦奈米管表面，可能是另一項影響N719染料吸附量使得光電特性劣化，造成兩種染料特性差異的原因。

In this work, hydrothermally treated titanium dioxide nanotube is studied. To apply the hydrothermal treatment, pre-sintering over 400℃ is required to prevent collapse of the nanotubes during the treatment. X-ray diffraction pattern showed that the titanium dioxide nanotubes after the hydrothermal treatment maintained anatase phase. By raising pre-sintering temperature or increasing the volume of the solution in the hydrothermal treatment, the crystallinity of the titanium dioxide nanotubes, the amount of adsorbed dye, and thus the performance of dye-sensitized solar cell were enhanced. Also, the influence of the pH of hydrothermal solution was studied. According to Fourier Transform Infrared spectroscopy and X-ray photoelectron spectroscopy, after the hydrothermal treatment at higher pH or at lower pH the amounts of Ti-OH and Ti-OH2 on the nanotube surface were increased and the amount of Ti-O- was decreased, and due to the transformation of the surface ends decreased dye adsorption and degraded solar energy harvesting efficiency were hence resulted. In addition, the characteristics of two different dyes, N3 and N719, adsorbed on hydrothermally treated nanotubes were compared. In general, solar cell using photoelectrode of N3 dye adsorbed on hydrothermally treated nanotubes had better performance than that of N719 dye. In spite of the differences on the molar extinction coefficients and the molecular sizes of the dye molecular, the performance difference between N719 and N3 could be further influenced by TBA+ from N719, which more easily occupied hydrothermally treated TiO2 nanotube surface at higher or lower pH and lead to deterioration of dye adsorption.