本研究利用P型高分子材料混摻不同結構之富勒烯作為有機太陽能電池主動層，探討富勒烯結構對有機太陽能電池光伏特性之影響。所使用之P型高分子材料分別為聚(3-己烷噻吩) (Poly (3-hexylthiophene), P3HT)以及Poly[N-9'-heptadecanyl-2 7-carbazole-alt-5 5-(4' 7'-di-2-thienyl-2' 1' 3'- benzothiadiazole)] ( PCDTBT)，N型則為三種不同結構之富勒烯，分別為茚-碳六十之雙加成物(Indene-C60 bisadduct, ICBA)、茚-碳六十之單加成物(Indene-C60 monoadduct, ICMA)以及碳六十衍生物([6,6]-phenyl C61-butyric acid methyl ester, PCBM)。分別使用氯苯(Chlorobenzene, CB)與鄰-二氯苯(1,2-dichlorobenzene, DCB)為溶劑，配製P型高分子與N型富勒烯之混合溶液，以旋轉塗佈方式製作塊材異質接面結構之有機太陽能電池。本研究利用吸收光譜、拉曼光譜、原子力顯微鏡與X光繞射光譜等儀器分析薄膜，透過以上分析探討主動層薄膜內部微結構變化與元件電特性之間的關係。
實驗結果顯示以P3HT為P型材料之太陽能電池中，P3HT:ICBA為主動層之元件具有最佳光電轉換效率，可達3.67%，主因其具有最大之開路電壓值(0.83 V)，而P3HT:ICMA與P3HT:PCBM兩組元件效率差異不大(約2.5%)。然而，在以PCDTBT為P型材料之太陽能電池中，PCDTBT:ICBA之元件效率最差(僅1.76%)，其開路電壓值最大(高達1.06 V)，但在短路電流密度與填充因子兩項參數上表現不佳，而PCDTBT:ICMA與PCDTBT:PCBM兩組元件效率則相近(約2.8%)。
利用光譜學方法分析不同結構富勒烯對主動層內微結構之影響。結果顯示在以P3HT:富勒烯主動層系統內，混摻ICBA易使P3HT在結晶區具有較佳之自組織能力；而富勒烯結構對P3HT於縱向堆疊之排列情形影響不大。然而，PCDTBT:富勒烯主動層系統內，混摻ICBA則易使主動層內P型與N型材料各自聚集，減少P-N接面之接觸面積，造成激子分離機率下降，影響元件效率。

In this study, the structural effects of the active layers on the photovoltaic characteristics of polymer-fullerene bulk heterojunction (BHJ) solar cells were investigated. To prepare the active layers of the BHJ solar cells, two kinds of conjugated polymers: poly (3-hexylthiophene) (P3HT) and poly[N-9'-heptadecanyl-2 7-carbazole-alt-5 5-(4' 7'-di-2-thienyl-2' 1' 3'- benzothiadiazole)] (PCDTBT) were used as the electron donor, and three kinds of fullerene derivatives: indene-C60 bisadduct (ICBA), indene-C60 monoadduct (ICMA), and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were used as the electron acceptor. The polymer-fullerene blended active layers were prepared by solution deposition via a spin-coating technique using 1,2-dichlorobenzene and chlorobenzene as solvents, respectively. We studied the correlation between the microstructure of the active layers and the photovoltaic properties of the solar cells. The active layers were characterized using absorption spectroscopy, Raman spectroscopy, atomic force microscopy and x-ray diffraction.

For the photovoltaic properties, we found that the P3HT-fullrene-based solar cells that were made using ICBA as the electron acceptor showed the best power conversion efficiency (PCE) of 3.67% and largest open-circuit voltage of 0.83 V. The devices with ICMA and PCBM as electron acceptor showed similar performance with the PCE of ca. 2.5%. For the PCDTBT-fullerene-based solar cells, however, the devices with ICBA exhibited the lowest photovoltaic performance with a PCE of 1.76% due to low short-circuit current density and inferior fill factor values. In contrast, the devices with ICMA and PCBM showed similar performance with the PCE of ca. 2.8%.

We studied the effects of the structure of fullerene on the microstructure of active layers. For the P3HT-fullerene blending active layers, no significant changes were observed in the vertical orientation of the P3HT. Spectroscopy analysis results revealed the addition of ICBA improved the self-assembling ability of the crystalline P3HT. However, when ICBA was used in the PCDTBT-fullerene systems, the P-type and N-type materials tended to separately aggregate, thereby creating a smaller P-N junction area, thus decreasing the probability of exciton dissociation. This provides a reasonable basis for the lowest PCE of the PCDTBT-ICBA solar cells.

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