Design and synthesis of dithieno[3,2‐b:2′3′‐d]pyrrole‐based conjugated polymers for photovoltaic applications: consensus between low bandgap and low HOMO energy level |
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Authors: | Min‐Min Shi Dan Deng Lin Chen Jun Ling Lei Fu Xiao‐Lian Hu Hong‐Zheng Chen |
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Institution: | 1. State Key Lab of Silicon Materials, MOE Key Laboratory of Macromolecule Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China;2. Department of Polymer Science and Engineering, School of Materials and Textile Engineering, Jiaxing University, Jiaxing 314001, People's Republic of China |
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Abstract: | A strategy of the fine‐tuning of the degree of intrachain charge transfer and aromaticity of polymer backbone was adopted to design and synthesize new polymers applicable in photovoltaics. Three conjugated polymers P1 , P2 , and P3 were synthesized by alternating the electron‐donating dithieno3,2‐b:2′3′‐d]pyrrole (D) and three different electron‐accepting (A) segments ( P1 : N‐(2‐ethylhexyl)phthalimide; P2 : 1,4‐diketo‐3,6‐diphenylpyrrolo3,4‐c]pyrrole; and P3 : thiophene‐3‐hexyl formate) in the polymer main chain. Among the three polymers, P2 possessed the broadest absorption band ranging from 300 to 760 nm, the lowest bandgap (1.63 eV), and enough low HOMO energy level (?5.27 eV) because of the strong intrachain charge transfer from D to A units and the appropriate extent of quinoid state in the main chain of P2 , which was convinced by the theoretical simulation of molecular geometry and front orbits. Photovoltaic study of solar cells based on the blends of P1 – P3 and 6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) demonstrated that P2 :PCBM exhibited the best performance: a power conversion efficiency of 1.22% with a high open‐circuit voltage (VOC) of 0.70 V and a large short‐circuit current (ISC) of 5.02 mA/cm2 were achieved. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 |
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Keywords: | conjugated polymers copolymerization energy levels heteroatom‐containing polymers polymer solar cells |
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