本論文使用聚乙烯亞胺(polyethyleneimine簡稱b-PEI) 做為反式有機太陽能電池之電子萃取層，研究b-PEI的製程參數對太陽能電池光伏特性的影響，並研究元件的操作穩定性，最後，則與傳統順式元件比較之，傳統順式元件一般使用poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT)為電荷萃取層。電池元件的主動層材料選用高分子聚３-已基噻吩[Poly(3-hexylthiophene-2,5-diyl)，P3HT]為電子施體與[6,6]-苯基-C61-丁酸甲酯 [(6,6)-phenyl C61-butyric acid methyl ester]為電子受體。本論文利用X光繞射光譜、原子力顯微鏡、紫外-可見光吸收光譜與拉曼光譜，研究主動層薄膜在不同製程參數的b-PEI層的微結構變化，並探討其與元件光伏特性的關聯性。

　 實驗結果顯示b-PEI的製程參數明顯影響反式有機太陽能電池的光伏特性，當使用甲醇為溶劑和180 oC的成膜溫度製作b-PEI 層，再將元件在150 oC進行熱退火處理，元件之光電轉換效率可達3.21%，優於傳統製程製作的順式有機太陽能電池（效率為2.46%）。結構分析發現b-PEI薄膜的製程參數會影響到後續主動層的微結構，在最佳製程參數的b-PEI薄膜上，P3HT有較佳的縱向結晶性與較短的共軛鏈長，且表面有較多突出區，有利電荷進行縱向傳輸，因此元件有較高的短路電流與較佳的光電轉換效率，優於使用PEDOT:PSS電荷萃取層之傳統順式元件。我們進一步發現使用b-PEI電子萃取層的反式元件的壽命遠優於傳統順式元件。

This thesis investigated the photovoltaic properties of poly(3-hexylthio -phene-2,5-diyl) (P3HT, electron donor):(6,6)-phenyl C61-butyric acid methyl ester (PCBM, electron acceptor)-based inverted-type bulk-heterojunction organic solar cells (BHJ OSCs) using polyethyleneimine (b-PEI) as the electron extraction layer. The effects of fabrication conditions of the b-PEI layer on the photovoltaic parameters and stability of the inverted-type BHJ OSCs were studied and then compared to the conventional P3HT:PCBM -based normal-type BHJ OSCs with poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) as a charge extraction layer. We studied the correlation between the morphology of the photo-active layer and the photovoltaic properties of the OSCs in terms of x-ray diffraction (XRD), atomic force microscopy, absorption spectroscopy, and Raman spectroscopy.

The results revealed that the fabrication conditions of b-PEI layer have significant effects on the photovoltaic properties of the inverted-type BHJ OSCs. A power conversion efficiency (PSC) up to 3.21% of the inverted-type BHJ OSCs was obtained when the b-PEI layer was prepared from methanol solution and baked at 180 oC, and then post-annealed at 150 oC. The photovoltaic performance was superior to conventional normal-type P3HT:PCBM-based BHJ-OSCs (PSC of 2.46%). Structural analysis results indicated that the b-PEI layer conditions have large effects on the structural properties of the P3HT:PCBM photo-active layer. With the optimized fabrication conditions of the b-PEI layer, we observed that the P3HT component in the photo-active layer exhibit a better crystallization along the a-axis and shorter effective conjugation length, thus benefiting charge transport to the electrode. The resulting inverted-type BHJ OSCs exhibit higher short-circuit current than that of the normal-type BHJ OSCs. Finally, we highlight that the inverted-type BHJ OSCs with the b-PEI layer exhibit improved operational stability compared to the conventional normal-type BHJ OSCs

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