高分子太陽電池的製程中，溶劑效應決定了主動層的形貌，故溶劑在元件製程中扮演相當重要的角色。本研究以氯苯、鄰-二氯苯與1,2,4-三氯苯為主動層溶劑，分別製備聚(3-己烷基噻吩)(P3HT)摻雜碳六十衍生物(PCBM)的高分子太陽電池，並藉改變主動層溶液濃度，使不同溶劑可製備相同厚度的主動層，以探討高分子太陽電池的主動層形貌對其元件電特性的影響。研究結果顯示P3HT結晶區的過度成長將導致激子分離率下降並截斷電子傳輸路徑，因而導致元件短路電流與填充因子下降；P3HT的平均有效共軛鏈長過於延展，將導致其最高已被占據分子軌域(HOMO)能階下降，使元件開路電壓下降。而以氯苯製備的主動層，具備適度的P3HT結晶區與共軛鏈長，因此獲致最佳的元件電特性。另外，經比較調整主動層厚度前後的元件，我們指出若要分析不同溶劑或者溶劑添加物對元件的影響，各主動層厚度需列為考量。

高分子太陽電池的開路電壓決定於p型材料的最高已被占據分子軌域(HOMO)與n型材料的最低未被佔據分子軌域(LUMO)的能階差。本研究引入具備高LUMO能階的新型碳六十衍生物：茚-碳六十的雙加成物(ICBA)，使用氯苯、二氯苯與三氯苯為主動層溶劑，製備P3HT:ICBA高分子太陽電池，並討論其主動層形貌與元件電特性，再與P3HT:PCBM元件比較。結果顯示主動層中ICBA的存在較PCBM不利於P3HT結晶區形成。因為ICBA具有較高的LUMO能階，可形成較高的元件內建電場，因此P3HT:ICBA元件表現出較高開路電壓與填充因子；而ICBA較差的電子遷移率則導致P3HT:ICBA元件有較低短路電流。另外，研究結果發現P3HT:ICBA元件的電流主要由電洞所貢獻; P3HT:PCBM元件的則由電子所貢獻。因此，於P3HT:ICBA元件中，隨著P3HT結晶區過度成長，我們並未觀察到明顯下降地填充因子。

Solvent effects play important roles in the fabrication of polymer solar cells because of their critical influence over the active layer morphology. In this thesis, we use chlorobenzene (CB), ortho-dichlorobenzene (DCB), and 1,2,4-trichlorobenzene (TCB) as solvents to prepare the active layers of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) for polymer solar cell applications. Tuning the solution concentration enables the preparation of P3HT:PCBM films with the same thicknesses using various solvents. Therefore, the correlations between active-layer morphologies and device performances could be found out: The short-circuit current density, open-circuit voltage, and fill factor of the device are high because of the small dead layer region, short P3HT conjugation length, and good percolation path for electrons in the active layer prepared using CB, respectively. We also demonstrate that the misleading conclusions will be brought out if we disregard the different thicknesses of the active layers that are fabricated using various solvents.

The open-circuit voltage of polymer solar cells is defined as the energy difference between the lowest unoccupied molecular orbital (LUMO) level of the n-type semiconductor and the highest occupied molecular orbital (HOMO) level of the p-type semiconductor. We introduce a novel fullerene derivative called indene-C60 bisadduct (ICBA), which LUMO level is 0.17 eV higher than that of PCBM. We use CB, DCB, and TCB as solvents to fabricate the P3HT:ICBA devices, and compare the active-layer morphologies and device performances between the P3HT:ICBA and P3HT:PCBM devices. We find that the presence of ICBA in the active layer is unfavorable to the formation of the P3HT crystal. The high built-in field in the P3HT:ICBA devices is due to the high LUMO energy level of ICBA, thus resulting in a high open-circuit voltage and a high fill factor. On the other hand, the low short-circuit current may be due to the low charge mobility of ICBA. Finally, we find that the currents of P3HT:ICBA and P3HT:PCBM devices are dominated by holes and electrons, respectively. That is why the large P3HT crystal does not affect the fill factor of P3HT:ICBA device as obviously as P3HT:PCBM system.

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