Novel Donor鈥揂cceptor Random Copolymers Containing Phenanthrocarbazole and Diketopyrrolopyrrole for Organic Photovoltaics and the Significant Molecular Geometry Effect on Their Performance

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• 作者：Zhiqiang Deng ; Lie Chen ; Feiyan Wu ; Yiwang Chen
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：March 27, 2014
• 年：2014
• 卷：118
• 期：12
• 页码：6038-6045
• 全文大小：483K
• 年卷期：v.118,no.12(March 27, 2014)
• ISSN：1932-7455

文摘

A series of donor鈥揳cceptor (D鈥揂) random copolymers PPC-T-DPP and PPC-TT-DPP based on electron-rich 6H-phenanthro[1;10,9,8-cdefg]carbazole (PC) and electron-deficient 3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) building blocks with two different linking units, thiophene (T) and thieno[3,2-b]thiophene (TT), were successfully synthesized. All of the copolymers show excellent light absorption, and their photoelectric properties can be easily adjusted by tailoring the molar ratio of PC to DPP. Among the polymer solar cells (PSCs) based on the copolymers with T linking unit, the PPC-T-DPP_1/2 (the molar ratio of PC:DPP = 1:2):PC₆₁BM ([6,6]-phenyl-C₆₁-butyric acid methyl ester) based device achieves the best efficiency of 2.0%. After replacing T with TT, a slightly enhanced power conversion efficiency (PCE) of 2.2% is obtained from the PPC-TT-DPP_1/2:PC₆₁BM-based device due to the better charge mobility of TT. However, with the addition of 1-chloronaphthalene (CN) to a volume ratio of 10%, the PCE of the device with PPC-T-DPP_1/2:PC₆₁BM is improved to 2.8%, even higher than the CN-treated PPC-TT-DPP_1/2:PC₆₁BM device (2.4%). The density functional theory (DFT) calculation results reveal that the incorporation of the axisymmetrical PC molecule with centrosymmetrical DPP unit together induces a large dihedral angle and big backbone torsion, and the more planar TT linkage seems to deteriorate molecular packing compared to the T unit, consequently leading to the worse performance.