Benzodithiophene-Based Polymers Containing Alkylthiophenyl Side Chains with Lowered HOMO Energy Levels for Organic Solar Cells

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• 作者：Meijie Fan ; Dr. Zhengkun Du ; Weiye Chen ; Deyu Liu ; Dr. Shuguang Wen ; Prof. Mingliang Sun and Prof. Renqiang Yang
• 刊名：Asian Journal of Organic Chemistry
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：5
• 期：10
• 页码：1273-1279
• 全文大小：1389K
• ISSN：2193-5815

文摘

In this paper, a novel donor based on alkylthiophenyl side-chained benzodithiophene (BDT) (M1) was first designed and synthesized to construct a series of conjugated polymers (P1, P2, P3) used in polymer solar cells (PSCs). P1, P2, and P3 were prepared by copolymerizing M1 with 4,7-di(4-(2-ethylhexyl)-2-thienyl)-2,1,3-benzothiadiazole (DTBT), quinoxaline, and diketopyrrolopyrrole (DPP), respectively. The optical electrochemical and photovoltaic properties of these polymers were investigated. Alkylthiophenyl substitution on the BDT building block is favorable for the low-lying highest occupied orbital (HOMO) level of polymers. The HOMO of these copolymers is clearly lowered to −5.49 eV, −5.34 eV, and −5.50 eV, respectively. Compared with reference polymers, our polymers show lowered HOMO energy levels (by 0.14 eV at least). This is very helpful to enhance the open-circuit voltage (V_oc) of the devices. Further, P2:PC₆₁BM exhibited an optimized power conversion efficiency (PCE) of 4.28 %, which is clearly higher than that of P1 (1.48 %) and P3 (1.9 %).