應用於染料敏化太陽能電池之無金屬有機染料於不同環境下之光譜動力學研究

Abstract

本論文可以分為兩部分，第一部分利用瞬態吸收、螢光光譜、時間相關單光子技術系統(Time- Correlated Single Photo Counting；TCSPC)和非等向性光譜技術來觀測OD0-OD2無金屬有機染料在THF溶液中不同濃度下的分子動力學行為。在THF溶液中，我們觀察到OD0-OD2無金屬有機染料濃度提高時，穩態吸收光譜會變寬且有紅位移的現象，在穩態螢光光譜觀察到OD0-OD2有機染料隨著激發波長不同會激發出不同的螢光光譜，當濃度提高時此現象更為明顯，推測是濃度提高形成聚合物所造成。在生命期的測量方面，我們分別利用435nm和375nm激發來有效的分辨出聚合物和單分子的生命期，同時也觀察到利用435nm激發會有很明顯的solvation現象。利用非等向性光譜技術擬合後得到的旋轉生命期(rotation lifetime)可以觀察到OD0-OD2有機染料整體體積會跟濃度成正比，表示這一系列染料在溶液中確實會形成聚合物。第二部份利用I-V量測系統，螢光上轉移技術和瞬態光電流/光電壓衰減光譜技術觀測OD0-OD2有機染料封裝成DSSC元件上的行為。I-V特性曲線可以觀察到V_OC，J_SC以及η的趨勢皆為OD2 >OD1 >OD0。利用螢光上轉移技術比較二氧化鈦和氧化鋁薄膜上的分子生命期，經過計算後可以得到電子注入速率，電子注入速率趨勢為OD0 >OD1 >OD2。瞬態光電壓/光電流衰減光譜技術則可以觀察到電荷重組速率為OD0 >OD1 >OD2，二氧化鈦導帶的相對位置則為OD2 >OD1 >OD0。我們綜合第二部份的實驗結果，可以得知OD2的導帶位置最高造成較高的V_OC，導帶的位置同樣會影響電子注入速率和電荷重組速率，導帶提高會降低電子注入速率和電荷重組速率。OD0-OD2有機染料改變二氧化鈦導帶的原因是染料分子在基態的極性大小和方向不同所造成。

We studied a series of organic dye, named OD0, OD1 and OD2 for their applications in dye-sensitized solar cells (DSSC). The structural between OD0, OD1 and OD2 are the peripheral derivations thiophene which contain of benzene on the diphenylamino group. In present study, the results show larger dyes with higher efficiencies. In addition, the device made of OD2 has a large open-circuit voltage (VOC > 0.8 V) similar to that of a Ru complex dye. In this study, we focused on understanding of the fundamental properties of the organic dye, and studying how the structure of the dye influenced the efficiency of DSSC. The results show that the dyes with larger size could help to improve the performance efficiency due to less aggregation and charge recombination. The results also show when OD2 was absorbed on TiO2, upward shift of the TiO2 conduction band, so as to gain a large open-circuit voltage. Longer electron lifetime and a lower injection yield was also observed of OD2. A dipole-moment was provided to explain the observed photovoltaic properties of the metal-free organic dye.