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  • 學位論文

用於高分子/二氧化鈦混摻系統太陽能電池的新穎低能隙導電高分子及表面改質劑的合成與鑒定

Synthesis and Characterization of Novel Low Band Gap Conducting Polymers and Surface Modifiers for Hybrid Polymer/TiO2 Solar Cells

指導教授 : 林唯芳
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摘要


本研究的目標是合成低能隙導電高分子及表面改質劑應用於高分子二氧化鈦混摻系統太陽能電池中。 一系列含有不同芴(fluorene)與環戊噻吩(cyclopentaditiophene)(CPDT)組成的共聚物利用Stille 交叉耦合方法合成出來。與純聚環戊噻吩的吸收光譜相比時,含有芴高分子之吸收光譜有藍移現象。此藍移現象會隨著芴在高分子中的濃度增加而增強。高分子中分別含25莫爾百分比、50莫爾百分比與75莫爾百分比例的芴時,高分子的能隙可以依序調至1.72 eV、1.82 eV與1.89eV。同時高分子的最高填滿軌域(HOMO)能階也如我們預期可隨著加入芴而有明顯降低現象,其可以增加太陽能電池之開路電壓值(Voc)。模擬的結果與實際實驗數據在光譜性質與電化學性質上有一致性的趨勢。藉由此簡單地改變高分子中的芴與環戊噻吩之組成,我們可以輕易的調整高分子的最高填滿軌域與能隙以便提升太陽能電池效率。 另外,在高分子與TiO2混摻太陽能電池中,我們合成導電小分子2-cyano-3-(5-(7-(thiophen-2-yl)-2,1,3-benzothiadiazol-4-yl)thiophen-2-yl)acrylic acid(W4)與(Z)-2-cyano-3-(5-(7-(5-(9,9-dioctyl-9H-fluoren-2-yl)thiophen-2-yl) benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)acrylic acid(W4-F)用於修飾TiO2表面。透過TiO2表面的修飾使元件效率由未改質前的0.44%大幅的上升至0.75%。如此顯著的提升主要歸因於W4與W4-F加強了TiO2與高分子間電荷的分離與傳導,降低電荷的再結合,顯著的增強太陽能電池的電流值。

並列摘要


The objective of this research is to design and synthesis novel low band gap conducting polymers and surface modifiers for hybrid polymer/TiO2 solar cell applications.A series of alternating copolymers consisting of different compositions of fluorene and cyclopentaditiophene(CPDT) were synthesized via Stille coupling. The absorption spectra of copolymers containing fluorene moiety showed a blue-shift of main peak as compared with that of CPDT‘s homo polymer PCPDTBT. Additionally, the effect of blue-shift observed in the absorption spectra increased with increasing the molar ratio of fluorene moiety. The band gap were 1.65 eV,1.72 eV,1.82eV and 1.89eV respectively when 0 mol%,25 mol%,50 mol% and 75mol% of fluorene moiety were induced into the polymer. At the same time, the HOMO levels of these polymers were significantly lowered which is desired property to improve the Voc of solar cell. The optical and electrochemical properties of these polymers are consistent with the molecular simulation results. By simply changing the composition between fluorene and cyclopentaditiophene in the polymer, we could easily tune the HOMO level and band gap of polymer. The resulting polymers have potential to improve the efficiency of solar cell. We also synthesized two molecules, i.e. W4 and W4-F, as the surface modifier of TiO2 nanorod. By modifying the surface of TiO2 nanorod with W4 or W4-F, the Jsc(short circuit current density)of device made from W4 or W4-F modified TiO2 nanorod increased substantially as compared with that using unmodified TiO2 nanorod. The power conversion efficiency increased significantly from 0.44% to 0.75% as the surface modifier was changed from pyridine to W4 or W4-F. The improvement of efficiency was due to the reducing of charge recombination and enhance of charge separation via the linkage of W4 and W4-F on the surface of TiO2 nanorod.

參考文獻


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