三-烷基噻吩和乳酸嵌段共聚物之分子自組裝奈米結構及在有機太陽能電池之應用

Abstract

本研究首先合成具有氫氧基末端基之聚-(3-己烷噻吩)及聚3-(6-溴己烷) 噻吩，再經開環聚合得到兩個聚噻吩嵌段共聚物P3HT-b-PLLA及P3BHT-b-PLLA，隨後利用微差掃描卡計(DSC)和紫外可見光光譜儀(UV-vis)鑑定兩個嵌段共聚物得到熱性質及光學性質，從P3BHT和PLLA嵌段之分子量控制得到符合柱狀結構自組裝比例之嵌段高分子，製作成薄膜後，以原子力顯微鏡觀察表面之形態證實其柱狀結構，再以氫氧化鈉水溶液除去PLLA嵌段得到多孔洞之薄膜。而在太陽能電池應用上，分為兩部份研究，第一部份利用P3BHT-b-PLLA具有自組裝形成奈米結構以及帶有溴官能基可進行光交聯的特性，製作太陽能電池雙層元件，元件結構為：ITO/V2O5/crosslinked P3BHT/porous P3BHT film /PCBM/Al，相較於對照元件(未進行PLLA裂解前)，元件效率從0.32%上升至0.51 %，Jsc從4.62 mA/cm2上升至6.06 mA/cm2，FF(填充因子)也由11.81 %提高至16.86 %。而第二部份的研究則是將P3HT-b-PLLA作為添加劑摻入P3HT/PCBM混摻接面結構元件，目的是想利用嵌段共聚物內分子不同的特性來修飾P3HT/PCBM接面，元件結構為：ITO/PEDOT:PSS/ P3HT:PCBM:P3HT-b-PLLA/Ca/Al，本研究分別於P3HT-PCBM異質接面中摻入0.5 wt%、1 wt%、1.5 wt%之P3HT-b-PLLA，其中摻入0.5 wt%元件相較於對照元件，元件效率從4.18%上升至4.49 %，Jsc從12.55 mA/cm2上升至12.77 mA/cm2，FF(填充因子) 也由57.41 %提高至58.63 %，同時本研究也從元件效率的衰減以及薄膜表面形態的研究中，證明了摻入嵌段共聚物P3HT-b-PLLA可提高太陽能電池元件之熱穩定性。

In this study, poly(3-hexylthiophene) and poly[3-(6-bromohexyl)thiophene] with hydroxyl end group were synthesized. Both polymers were further polymerized with L-lactic acid via ring-opening polymerization to obtain the block polymer P3HT-b-PLLA and P3BHT-b-PLLA. In order to form the cylinder nano-structure for the block copolymers, the wt% of PLLA block was controlled between 20-25%. The synthesized block copolymers were characterized by DSC and UV spectroscopy to study their thermal and optical properities. The spin-casted thin film of P3BHT-b-PLLA was investigated by AFM to prove its cylinder morphology. After exposure with UV radiation, the P3BHT block was crosslinked and the PLLA block was etched with NaOH solution, resulting in a P3BHT porous film. This porous P3BHT was used to fabricate a bi-layers solar cell with the configuration of ITO/V2O5 /porous –P3BHT/PCBM/Al. This nano-ordered OPV device shows a Voc of 0.5 V, a Jsc of 4.62 mA/cm2, a FF of 16.86 %, and a PCE of 0.51 %. In the second part of this study, we used P3HT-b-PLLA as an additive which was blended with P3HT and PCBM to modify the bulk heterojunction layer of an OPV device. The wt% of P3HT-b-PLLA was 0.5 wt%,1 wt%, and 1.5 wt%. The OPV device containing 0.5 wt% of P3HT-b-PLLA showed the highest PCE value of 4.49 %. If we compared its performance with the performance from the OPV device without P3HT-b-PLLA additive, its Jsc increases from 12.55 to 12.77 mA/cm2, FF increases from 57.41 to 58.63 %, and PCE increases from 4.18 to 4.49 %. The OPV device containing P3HT-b-PLLA also showed better thermal stability after long time thermal treatment.