高分子-富勒烯太陽能電池利用異構化之對稱型拉電子基團達成同時提升開路電壓、短路電流、光電轉換效率之研究

本論文為了增強高分子的拉電子基團能力，設計兩種互為異構物的拉電子基團 (TTαCN、TTβCN)，其是由兩個acrylonitrile (ACN) 與thienothiophene (TT) 所組成的對稱且非併環之拉電子結構，以延長共軛長度，縮小高分子之吸光能隙 (Eg)。再與benzodithiophene (BDT) 聚合得到兩種共軛高分子 (pBαCN、pBβCN)。當ACN官能基的連接位置不同時，其電子共振式會有不同的共振方向之傾向，使高分子有不同的電荷分佈方式，如TTαCN之ACN基團靠近單元，其電子呈分散且片段的分佈；TTβCN之ACN基團靠近thiophene單元，其電子呈集中且一片的分佈。本論文利用此種不同電荷分佈之拉電子基團，以調整其拉電子能力，進而改變高分子之分子能階，達成一高分子同時擁有深的HOMO能階、小的Eg，以讓其太陽能電池元件能同時增加VOC與JSC，使元件之PCE增加。利用UV-Vis、CV、AC-2、DFT理論計算、TEM、GIWAXS、hole only SCLC等，探討拉電子基團之電荷分佈差異對共軛高分子之分子能階、高分子結晶性、電洞遷移率等影響，發現聚集且一片式電子分佈之pBβCN有較強的拉電子基團、較深的HOMO能階、較小Eg，並且pBβCN有較強的偶極矩與庫倫作用力，使pBβCN有較強的高分子-高分子間作用力，令其有較佳的高分子結晶能力、電洞遷移率。最後將兩材料製成太陽能電池之元件，並以TEM、GIWAXS、hole only SCLC、PL quencing研究morpology變化，發現pBβCN有較強的高分子-PC71BM間作用力，使pBβCN與PC71BM有較好互溶性，主動層不需添加劑即可有理想的雙連續相分離結構，其元件之PCE = 7.94%。當主動層混摻DPE添加劑時，pBαCN元件PCE = 7.68%，其VOC = 0.91 V、JSC = 13.8 mA/cm2、FF = 61.9%；pBβCN元件PCE = 9.27%，其VOC = 0.96 V、JSC = 15.6 mA/cm2、FF = 61.8%，此9.27%光電轉換效率是目前含ACN高分子-PC71BM系統的最高值。

關鍵字

有機光伏電池；高分子太陽能電池；富勒烯； BDT ；丙烯腈

並列摘要

We designed and synthesized two isomeric electron accepting unit, TTαCN and TTβCN, these has two separate acrylonitrile (ACN) moieties as the electron acceptor, which are bridged by a π-conjugated thienothiophene (TT) central core and end-capped by a thiophene (T) unit. The copolymers (pBαCN, pBβCN) were copolymerized with these isomers and benzodithiophene. There are various electron distributions in both copolymers with the different structural moieties π-conjugated to the ACN unit. To understand the structural effect of isomeric ACN on the photophysical properties and PSC performance of two copolymers, the thermal, electrochemical, and UV-Vis absorption spectroscopic properties were systematically investigated, together with GIWAXS and TEM studies as well as DFT theoretical calculations. The pBβCN PSCs were found to exhibit a better PCE of 9.27% than a PCE of 7.68% of pBαCN by showing a higher VOC of 0.96 V and a higher JSC of 15.62 mA/cm2 at the same time. We have obtained insightful information to elucidate why the β-isomer of the copolymer (pBβCN) can achieve a high VOC along with a high JSC, and hence a relatively high power conversion efficiency of 9.27%, in [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM)-blended bulk heterojuction polymer solar cells.

並列關鍵字

organic photovoltaics ； polymer solar cells ； fullerene ； benzodithiophene ； acrylonitrile ； cyanovinylene

參考文獻

Source: Retrieved Jane 27, 2018, from http://dailysoleil.com/global-solar-cell-paste-market-growth-rate-end-user-application-competitive-landscape-analysis-2018-2023/