| 摘要: | 自1990年後，可做為N-型材料之富勒烯衍生物的合成因為高分子太陽能電池的發展開始受到注意，但受限於富勒烯本身的反應性，難以藉由調整取代基來改變富勒烯衍生物的性質。本研究不調整取代基種類改以改變取代基數目及更換共軛陰離子的方式來改變富勒烯衍生物的性質，因此合成C60-(RT2+)2(4Cl-)、C60-(RT2+)2(4Br-)、C60-(RT2+)2(4I-)、C60-(RT2+)6(12Cl-)、C60-(RT2+)6(12Br-)、C60-(RT2+)6(12I-)六個離子性富勒烯衍生物。這些富勒烯衍生物因取代基數與共軛陰離子不同而有不同的溶解度，當固定取代基數目時，在甲醇中的溶解度大小為C60-(RT2+)n(2nI-) > C60-(RT2+)n(2nBr-) > C60-(RT2+)n(2nCl-)；若共軛陰離子相同時，則富勒烯含有六個取代基的溶解度大於含有兩個取代基。熱重分析(TGA)測得所合成出的離子性富勒烯衍生物的熱裂解溫度約170 oC。UV-Vis吸收光譜顯示所合成的離子性富勒烯衍生物的最大吸收波長落在230到250 nm之間並經由Tauc plot計算出C60-(RT2+)2(4Cl-)、C60-(RT2+)2(4Br-) 、C60-(RT2+)2(4I-)、C60-(RT2+)6(12Cl-)、C60-(RT2+)6(12Br-)、及C60-(RT2+)6(12I-)的energy gap (Eg)分別為2.08 eV、2.04 eV、2.07 eV、1.88 eV、1.80 eV、及1.83 eV。由方波循環伏安法的數據計算得到C60-(RT2+)2(4Cl-)、C60-(RT2+)2 (4Br-) 、C60-(RT2+)2(4I-)、C60-(RT2+)6(12Cl-)、C60-(RT2+)6(12Br-)、C60-(RT2+)6(12I-)的最低無電子分子軌域(LUMO)能階分別為-4.00 eV、-4.01 eV、-4.12 eV、-3.75 eV、-3.66 eV、與-3.61 eV。配合吸收數據求得最高電子占據分子軌域(HOMO)能階則分別為-6.08 eV、-6.05 eV、-6.19 eV、-5.63 eV、-5.46 eV、與-5.44 eV。由C60-(RT2+)2(4X-)和C60-(RT2+)6(12X-)的能階得知，當共軛陰離子固定時，在取代基數目增加時，富勒烯旁邊帶負電的碳原子數目增加使LUMO較高。在共軛富勒烯陽離子有同數目的取代基下，因為陰電性的排序為碘<溴<氯，把電子給共軛富勒烯陽離子的能力排序為碘>溴>氯，因此C60-(RT2+)6(12I-)有最高的LUMO和HOMO能階。;Fullerene derivatives, have attracted a great attention due to the development of polymer solar cells, can be used as N-type materials for polymer solar cells. However, due to the limited reactivity of fullerene, it is difficult to change the properties of fullerene derivatives by changing the substituents. This study intends to change the properties of fullerene derivatives by changing the number of substituents and counter anions. Six ionic fullerene derivatives, C60-(RT2+)2(4Cl-), C60-(RT2+)2(4Br-), C60-(RT2+)2(4I-), C60-(RT2+)6(12Cl-), C60-(RT2+)6(12Br-), and C60-(RT2+)6(12I-) were synthesised. When the number of substituents are fixed, the order of the solubility in methanol is C60-(RT2+)n(2nI-) > C60-(RT2+)n (2nBr-) > C60-(RT2+)n(2nCl-). If the counter anions are the same, the solubility of fullerene derivative containing six substituents is bigger than that containing two substituents. Thermogravimetric analysis (TGA) reveals the thermal staility of the six ionic fullerene derivatives is all about 170 oC. The UV-Vis absorption spectra show that the maximum absorption wavelength (λmax) of the synthesized ionic fullerene derivatives falls between 230 and 250 nm. The energy gaps (Egs) of six ionic fullerene derivatives estimated from the absorption Tauc plot are 2.08 eV, 2.04 eV, 2.07 eV, 1.88 eV, 1.80 eV and 1.83 eV for C60-(RT2+)2(4Cl-), C60-(RT2+)2(4Br-), C60-(RT2+)2(4I-), C60-(RT2+)6(12Cl-), C60-(RT2+)6(12Br-), C60-(RT2+)6(12I-), respectively. The lowest unoccupy molecular orbital (LUMO) of six ionic fullerene derivatives are calculated from the square wave cyclic voltammetry are -4.00 eV, -4.01 eV, -4.12 eV, -3.75 eV, -3.66 eV, and -3.61 eV. The highest occupy molecular orbital (HOMO) to be -6.08 eV, -6.05 eV, -6.19 eV, -5.63 eV, -5.46 eV, and -5.44 eV. According to the energy levels of C60-(RT2+)2(4X-) and C60-(RT2+)6(12X-), when the counter anion is the same, when the number of substituents increases, the fullerene cations have less negative charge, therefore the increasing in the number of substituents makes the LUMO level higher. When the fullerene has the same number of substituents, the order of the electronegativity is iodine < bromide < chlorine, the electron donating ability is in the order of iodine > bromine > chlorine, consequently C60-(RT2+)6(12I-) have the highest LUMO and HOMO energy levels. |
