A Study of Various Photosensitizers for Dye-Sensitized Solar Cells

[[abstract]]本篇論文有系統的設計合成兩大系列有機光敏劑並應用於染料敏化太陽能電池的研究。首先以實驗室已發表鋅紫質光敏劑 LD14 為基礎，合成具不同長碳鏈之鋅紫質光敏劑 LD14-C8 與 LD14-C4，並探討長碳鏈對於紫質光敏劑其光電轉換效率之影響。改變紫質光敏劑長碳鏈的長度對於其紫外光-可見光光譜與螢光放射光譜的性質並沒有太大影響。分子模擬的結果則顯示，LD14 的長碳鏈較長可以完整纏繞紫質大環結構，減少分子堆疊的現象，而增進光電總轉換效率。另一系列為合成具不同拉電子基集團的有機光敏劑，並探討拉電子基集團對於其應用於染料敏化太陽能電池之影響。DOA-An-CNPE1 具有較長的共軛結構，導致其在紫外光-可見光吸收光譜表現較為紅移；電化學與理論計算的研究中顯示，具有不同拉電子集團的有機光敏劑其 LUMO 能階皆高於半導體導帶，利於染料分子躍遷至激發態後電子的傳遞。其光電轉換效率趨勢為 DOA-An-PE1 > DOA-An-1FPE1 > DOA-An-CNPE1 > DOA-An-2FPE1 > DOA-An-CF3PE1，顯示於 anchoring group 接上拉電子基無法提升光電轉換效率。其中具有最高光電轉換效率光敏劑 DOA-An-PE1 效率可以達 4.96%，大約為 N719 的 64%。[[abstract]]We systematically designed and synthesized two series of phosensitizers for dye-sensitized solar cell applications. Firstly, we prepared three porphyrin dyes with various alkoxyl chains, labelled as LD14, LD14-C8, and LD14-C4, in order to address the effect of alkoxyl lengths. LD14, LD14-C8, and LD14-C4 show nearly identical UV-vis and fluorescence emission spectra in THF. This indicates that the effect of the alkoxyl chains on UV-vis absorption and fluorescence emission spectra are very small. Based on the molecular simulations results, we demonstrated that suitable long alkoxyl chains are capable of wrapping the porphyrin core, thus resulting in decreased dye aggregation and improved photovoltaic performance. Secondly, we synthesized a series of organic dyes bearing various electron-withdrawing group for dye-sensitized solar cell applications. DOA-An-CNPE1 exhibits slight red shift in the UV-vis spectra, consistent with the more conjugated structure. The LUMO levels of these dyes were sufficiently higher than the conduction band of TiO2. The overall efficiencies of the devices show the trend of DOA-An-PE1 > DOA-An-1FPE1 > DOA-An-CNPE1 > DOA-An-2FPE1 > DOA-An-CF3PE1. DOA-An-PE1 shows the best performance η value 4.96%, approximately 64 % of that of N719.[[note]]碩