含有1,3-環己二烯π共軛骨架的有機雙極性染料用於染料敏化太陽能電池之研究

Abstract

本篇論文分為三個研究主題，第一個研究主題是我們研發以1,3-環己雙烯當作主要骨架的有機化合物染料來當作染料敏化太陽能電池的材料，並測試、探討其物理性質，以作為將來發展類似結構時的依據。在這些自行合成的染料結構中，除了 16 和 45 的結構，其他染料結構均包含了1,3-環己二烯的架構，希望藉由此環形的架構增加染料分子堆疊在二氧化鈦的程度，使染料在二氧化鈦上的吸附量增加，但是卻相對減少共軛分子間堆疊時常見到的 π – π 堆積作用力，進而增加染料的轉換效率。在物理性質方面，我們分別測試了染料個別的吸收光譜、螢光激發光譜和電化學性質。同時也將其製作成染料敏化太陽能電池的元件，利用太陽光模擬及特定波長光束輸出系統進行光電轉換效率與單色光轉換效率的測試，其中利用 14a 製備的元件其光電轉換效率可達到4.4 %，為利用 N719 製備元件的70 % (η = 5.87 %)，也從4b和其對照組 (16 和 45) 應証了環己二烯結構的優點。 在第二個主題中，我們探討了具有 TICT 態的染料對於 DSSCs 的效率影響，同時以相關數據證明了 4b 在激發態時會有 TICT 態。 TICT 態會使分子的偶極距增大，也會阻礙分子內電子的再結合。從相關的物性測試中，得知 D-π-A 分子具有 TICT 現象時會影響 Jsc 的數值，進而提高染料敏化太陽能電池的元件效率。 第三個題目是我們設計兩種新型 D-D-π-A 型式的有機染料，其中 D-π-A 的架構和第一個題目的結構 (4b和4c) 相似。我們希望藉由 D-D-π-A 的架構擴大染料的吸光範圍及消光系數，另一方面則是減少染料分子間的堆疊及提高熱穩定性，進而增加染料的轉換效率。目前此部份研究進行至化合物的合成。We have explored three topics in this study. In the first topic, we synthesized eight organic dyes (4a、4b、4c、9、14a、14b、16、45 ) for dye-sensitized solar cells (DSSCs) applications. Their physical properties were investigated. Except for dyes 16 and 45, which serve as model compounds, the other dyes all possess 1,3-cyclohexdiene conjugated units in the structural skeleton. One obvious advantage of employing 1,3-cyclohexadiene unit in the framework of light-harvesting dyes is the essential planar conformation in the structural skeleton which yields more dense packing of the dyes adsorbed on TiO2 surface. All of these compounds were characterized by UV/vis, fluorescence spectroscopy, and cyclic voltammetry. The cell performances and incident photo-to-current efficiencies of these compounds were inspected using the AM 1.5 simulated solar light and irradiation of monochromic light system. The highest conversion efficiency of the DSSCs based on dye 14a can reach up to 4.4 %. (70 % of the standard N719 dye, η= 5.87 %) In the second topic, we designed dye 32 as a model for assessing the role of the twisted intramolecular charge transfer (TICT) state played in the conversion efficiency of the DSSCs. TICT state allows the efficient charge-separation and slows down the unwanted charge-recombination processes. Their physical properties were detailed investigated and correlated the TICT state with the photovoltaic process of DSSCs. Finally, we designed two types of D-D-π-A organic dyes for DSSCs. Different carbazolyl groups were inserted to the structure to form the D-D-π-A compounds. On one hand, we expected that the absorption region can be extended and the molar extinction coefficient can be enhanced comparing with the D-π-A structure. On the other hand, these dyes may benefit from lower tendency to aggregate and display better thermo-stability.