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  • 學位論文

液晶材料與苯並咪唑衍生物作為液態和膠態電解質之添加物對染料敏化太陽能電池長效穩定性影響

Impact of liquid crystals and bis-benzimidazole derivative used as liquid and gel electrolyte additives on the performance and long-term stability of dye-sensitized solar cells

指導教授 : 楊重光 黃聲東
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摘要


本論文研究重點是將苯並咪唑衍生物(Bis-benzimidazole derivative)、向列型液晶(Nematic liquid crystal)和膽固醇型液晶(Cholesteric liquid crystal)作為電解質添加物,分別製備成液態電解質和以聚二氟乙烯-六氟丙烯(PVDF-HFP)為基礎的膠態電解質,目的在改善染料敏化太陽能電池之光電轉換效率與克服液態電解質因易揮發與封裝困難導致的漏液問題。藉由Solar simulator、IPCE與EIS等儀器,分析探討不同添加物對電池光電轉換效率的影響。 實驗發現,苯並咪唑衍生物(1,1'-(1,8-Octanediyl)bis[benzimidazole], ODBB-8),可有效提升電池之FF與Voc,判斷該添加物因分子排列方式於電解質中形成二維通道,而該傳遞通道將有利於I-/I3-的傳輸,使得以增加電池內部電子交換速率與降低電池整體串聯電阻,達到維持不錯的Jsc和增加FF的效果。且該添加物亦會影響二氧化鈦導電帶之能階,使得電池Voc亦有所上升,也因此有效提升電池之光電轉換效率。以膠態電解質為例,在太陽光模擬光源100mW/cm2照射下可得到Jsc=17.22mA/cm2、Voc=0.73V、FF=0.64、η=8.06±0.20% 的轉換效能。另一添加物膽固醇液晶Cholesteryl pelargonate,雖會妨礙電解質中I-/I3-的電化學行為,但因為該液晶添加物於電解質內部形成光捕捉系統,使得以提高入射光於電池內部的光繞路徑,促使電池之Jsc明顯上升連帶提升電池之光電轉換效率。 最後,在比較本實驗各條件之液態與膠態電解質,其組裝的太陽能電池長效穩定性部分,驗證結果發現在相同添加物條件下,膠態電解質之長效穩定性可優於液態電解質達5~10%。此外不同電解質添加物將會明顯影響電池的長效穩定性表現。以添加物ODBB-8的膠態電解質為例,電池經過1000小時(50mW/cm2、55℃)老化測試後可維持61%的穩定性,相較未添加電解質的54%有明顯之提升。

並列摘要


The focus of this thesis is to improve the energy conversion efficiency of dye-sensitized solar cells (DSSC) and to overcome the leakage problem due to the evaporation and sealing difficulties caused by the liquid electrolyte. In this study, we prepared the electrolytic additives of bis-benzimidazole derivative, nematic liquid crystal and cholesteric liquid crystal, and introduced them into the liquid electrolyte and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) based gel electrolyte for DSSC. Further, the effects of electrolytes are analyzed by the solar simulator, IPCE and EIS on the photovoltaic performance of DSSC. It was found that the bis-benzimidazole derivative (1,1'-(1,8-Octanediyl)bis [benzimidazole] ) (ODBB-8) can effectively enhance the Voc and FF of DSSC, which is caused by the formation of two-dimensional channel due to ODBB-8 in the electrolyte. This two-dimensional channel conducive to I-/I3- transmission and so increase the internal electronic exchange rate and reduce the series resistance, which maintain Jsc and increase FF. The ODBB-8 additive also affects the conduction band of the TiO2 that increase in Voc, resulting in the higher energy conversion efficiency of DSSC. A good conversion efficiency of 8.06±0.20% with Jsc of 17.22mA/cm2, an Voc of 0.73V and FF of 0.64 under illumination of 100mW/cm2 was obtained for the DSSC with gel electrolyte containing ODBB-8 derivative. Furthermore, the cholesteric liquid crystal additive (Cholesteryl pelargonate) although would hinder I-/I3- electrochemical behavior in the electrolyte, it could also promote Jsc and enhance the energy conversion efficiency of DSSC, because the formation of the light trapping scheme in the electrolyte. Finally, the evolution of energy conversion efficiencies with time in days for both the DSSC with gel electrolyte in absence and presence of ODBB-8 at the 50 mW/cm2, 55℃.The result in the efficiency of the DSSC containing 0.015M ODBB-8 observed 61% after 1000 hrs(50mW/cm2, 55℃), whereas that in absence of ODBB-8, the energy loss is 54%. It was demonstrated that the addition of ODBB-8 can improve the long-term stability of DSSC.

參考文獻


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