倒置有機無機混成太陽能電池其主動層形貌
改良與分析

人類在近年來將面對到的最大問題為能源短缺，由於石油藏量與日漸減，價格卻是不停上升，為了填補能源缺口，有多種可行的替代性能源成為各國研究的重點，太陽能幾乎取之不盡的特性，使得太陽能電池被視為能夠填補能源缺口的可行方案之一。而新發展高分子太陽能電池由於其重量輕、可撓性等性質且可大面積低成本製程，引起了廣泛的注意。但在高分子太陽能電池中，施體(Donor)和受體(Acceptor)必須要有好的奈米交錯結構，才能得到較高效率。此奈米交錯結構通常是相當雜亂，不易控制。在此篇論文中，透過許多實驗之探討，發現使用CB和DCB兩種溶劑形成混合溶劑來製作倒置結構高分子太陽能電池，可以使元件特性改善許多，論文中深入討論CB和DCB兩種溶劑對奈米交錯結構的影響。現今高分子太陽能電池主動層最常使用的主動層材料為P3HT/PCBM，P3HT的最高分子佔有軌道(HOMO)值(-5.0eV)和PCBM的最低未被分子佔有軌道(LUMO)值(-3.91eV)的差值非常的小。此缺點限制了元件的開路電壓(Voc)，因此使得元件的效率提升受到限制。為了提升開路電壓，一種新的n型富勒烯衍生物Indene-C60 bisadduct(ICBA)被提出，此種新的n型材料因為擁有較高的最低未被分子佔有軌道(LUMO)值(-3.74eV)比PCBM高0.17eV，因此可使元件的開路電壓有效的提升，進而提升元件效率。從另外一方面來看，P3HT因為其能隙只有2eV，限制了太陽光譜的吸收，使短路電流也受到限制，造成元件效率無法再提升，因此最近許多不同種類的低能隙材料來取代P3HT，藉由降低能隙來增加長波段光子的吸收提升短路電流，使元件的效率更進一步的提升。因此論文內容主要分成兩個主動層系統:其一是ICBA/P3HT，可使元件擁有較高的開路電壓。另一個是PBDTTT-C/PC71BM，可增加長波段光子的吸收因此使元件有較高的短路電流。在用ICBA/P3HT為主動層的系統下。本論文藉由DCB和CB形成混合溶劑來提高對於ICBA的溶解度，使得主動層溶液中的溶解不完全的大顆溶質顆粒減少使得主動層的成膜較為完整，且加入導電高分子PVK來改善因為不同溶劑所造成的水平相分離，以及利用不同溶劑比例來調整主動層乾燥時間藉此控制主動層厚度，最後在氮氣下對元件進行後退火。藉由以上的改進使得元件的開路電壓從0.66V提升到0.82V且效率由2.60%提升到4.27%。另外在用PBDTTT-C/PC71BM為主動層的系統下。本論文使用DCB和CB形成混合溶劑作為主動層的溶劑，並在加入DIO作為溶劑添加劑製作倒置結構高分子太陽能電池。混合溶劑的使用讓主動層的形貌獲得改善因此有較好的載子傳輸，之後再對主動層的厚度以及中介層氧化鉬的厚度進行最佳化，藉由以上的改進，使元件的短路電流從3.82 mA/cm2提升到13.50 mA/cm2，填充因子從33%提升到57%，也因此使元件光電轉換效率從0.92%提升到5.35%。

關鍵字

倒置高分子太陽能電池；混合溶劑； Indene-C60 bisadduct( ICBA) ； PBDTTT-C ；主動層形貌

並列摘要

The humanity’s most important problem is the energy shortage. Due to the increasing oil price, several renewable energy sources are investigated to fill the energy requirement gap between demand and supply. Polymer solar cells had been one of the most promising green energy technologies due to the possibility of achieving large-area, lightweight and flexible devices with low fabrication cost. The device performed better power conversion efficiency when the nano-interpenetrating networks between donor and accptor was better. However, we had difficult to control the disorder nano-interpenetrating networks. In this work, we found that we used CB and DCB as mixed solvent to fabricate the inverted polymer solar cell to enhence the performance of device through many experimental investigations. Moreover, we analyzed the effects of mixed solvent on nano-interpenetrating networks. One is P3HT/ICBA, which leads to higher open voltage of device. Another is PBDTTT-C/PC71BM, which harvests more sunlight and leads to higher short-circuit current density of device. With P3HT/ICBA as active layer, we used CB and DCB as mixed solvent to fabricate the inverted polymer solar cell to enhance the solubility of ICBA in photoactive ink. Furthermore, we added conductive polymer polyvinylcarbazole (PVK) to reduce the horizontal phase separation caused by different boiling point of solvents. In addition, we used different ratio of CB and DCB to control the dried time of active layer. In the end, we treated the device with post annealing. By the above improvements, the open circuit voltage of device can be enhanced from 0.68V to 0.82V and the (PCE) from 2.60% to 4.27%. With PBDTTT-C/PC71BM as active layer, we used CB and DCB as photoactive ink to fabricate the inverted polymer solar cell. With mixed solvent, The morphology of active layer was improved, which causes better transport of carrier. In addition, we optimize the thickness of active layer and the thickness of MoO3. By the above improvements, the short-circuit current density of device enhanced from 3.82 mA/cm2to 13.50 mA/cm2 and the power conversion efficiency from 0.92% to 5.35%.