2,2′-Bis(1,3,4-thiadiazole)-Based π-Conjugated Copolymers for Organic Photovoltaics with Exceeding 8% and Its Molecular Weight Dependence of Device Performance

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• 作者：Seijiro Fukuta ; Jooyeok Seo ; Hoyeol Lee ; Hwajeong Kim ; Youngkyoo KimMoonhor Ree ; Tomoya Higashihara
• 刊名：Macromolecules
• 出版年：2017
• 出版时间：February 14, 2017
• 年：2017
• 卷：50
• 期：3
• 页码：891-899
• 全文大小：576K
• ISSN：1520-5835

文摘

A series of novel π-conjugated copolymers based on 2,2′-bis(1,3,4-thiadiazole) (BTDz) have been developed. Among them, the BTDz-based donor–acceptor alternating copolymer with the (E)-1,2-di(3-(2-ethylhexyl)thiophene)vinylene donor unit (PBTDzTV) exhibited a high solubility and high crystallinity. PBTDzTVs favorably self-assembled, forming face-on and edge-on multibilayer structures in thin nanoscale films. The relative volume fractions of these structures varied depending on the polymer’s molecular weight. The higher molecular weight polymer formed a higher volume fraction of the face-on structure; in particular, the polymer with a 26.6 kDa of number-average molecular weight made only the face-on structure. The device performance was improved as the polymer molecular weight and the volume fraction of the face-on structure increased. The bulk-heterojunction photovoltaic device based on PBTDzTV:PC₇₁BM demonstrated the high power conversion efficiency (PCE) of 8.04% when the device was fabricated with the highest molecular weight polymer having the face-on structure.