紫質敏化太陽能電池之染料共敏化分子工程

Abstract

在本論文中，我們呈現與暨南大學林敬堯教授實驗室以及中興大學葉鎮宇教授實驗室共同合作之成果，不同於以往添加共吸附劑防止染料堆疊和電子攔截逆反應的策略，我們在紫質染料meso位置的苯環上，修飾在鄰位或間位的烷氧長鏈取代基，研究其結構對於染料敏化太陽電池光電轉換效率之影響。以林教授實驗室所合成之LD11-LD14染料為例，我們的研究結果顯示，修飾上鄰位的烷氧長鏈取代基後可以較有效地防止染料堆疊以及減緩電子攔截的逆反應，使元件的光電轉換效率提升。其中，LD14之最佳化元件效率可達10.2 %。 為了彌補單一染料吸收範圍不足的缺點，在本論文中，我們以染料共敏化的方式，將多種吸光範圍不同的染料共吸附到二氧化鈦上，使元件具備全光譜吸收的能力。其中LD12/CD5系統之最佳化元件效率可達9.0 %，在經過元件動力學的分析後發現，CD5染料有助於改善紫質染料堆疊行為。另外，我們研究YD2-o-C8/CD4/YDD6三種染料的共敏化系統，將元件吸光範圍更進一步延伸，包含的波長範圍從350 nm到800 nm之間屬於全光譜吸收。藉由改變溶液之染料分子莫耳比例，可以調控在二氧化鈦上之各染料的吸附量，使染料堆疊的情形獲得改善，其中YD2-o-C8/CD4/YDD6共敏化系統之最佳比例為20/5/1。經過元件最佳化，YD2-o-C8/CD4/YDD6系統之光電轉換效率可為10.3 %。

In this thesis, we present photovoltaic results for various porphyrin molecules as potential sensitizers for dye-sensitized solar cells (DSSC). A new concept to design a zinc porphyrin sensitizer with two phenyl groups at meso -positions of the macrocycle bearing two ortho-substituted long alkoxyl chains is intorduced to protect the porphyrin core for a retarded charge recombination and also to decrease effectively the dye aggregation for an efficient electron injection. In the present work, such a molecular design was applied for a push–pull porphyrin (LD14) which is synthesized by Prof. C. Y. Lin of NCNU to attain an exceptional cell performance, □ = 10.2 %. In the second part of this thesis, we present a rational design of two co- sensitization systems using two (LD12 and CD5) or three dyes (YD2-o-C8, CD4 and YDD6), for which the co-sensitized dyes have complementary adsorption spectra, to improve the device performance for porphyrin-sensitized solar cells. Upon optimization, the device made of LD12+CD5 yielded ƞ = 9.0%. We found that CD5 plays a role to retard charge recombination efficiently based on the results obtained from intensity-modulated photovoltage spectral measurement. In order to further enhance the light-harvesting ability, we use the near-infrared dye YDD6, synthesized by C. Y. Yeh of NCHN, co-sensitized with YD2-o-C8 and CD4. After well controlled the amounts of dye loading for these three dyes, we are able to optimize the device made of the YD2-o-C8/CD4/YDD6 system yielding ƞ =10.3 %.