A theoretical exploration of the effect of fluorine and cyano substitutions in diketopyrrolopyrrole-based polymer donor for organic solar cells |
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| Affiliation: | 1. Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Chang Chun, 130024, Jilin, PR China;2. Department of Chemistry, Capital Normal University, Beijing, 100048, PR China;1. Department of Chemistry, Payame Noor University (PNU), P.O. Box, 19395-3697, Tehran, Iran;2. Department of Engineering Science, College of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran, Iran;1. Shijiazhuang Mechanical Engineering College, Shijiazhuang 050003, China;2. Department of Graduate Management, Equipment Academy, Beijing 101416, China;3. Key Laboratory of Advanced Materials (MOE), Department of Chemical Engineering, Tsinghua University, Beijing 100084, China;1. Department of Polymer Engineering, Pukyong National University, Yongdang-Dong, Nam-gu, Busan 608-739, Republic of Korea;2. Materials Science & Engineering, Pukyong National University, Yongdang-Dong, Nam-gu, Busan 608-739, Republic of Korea;1. Gansu Key Laboratory of Polymer Materials, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China;2. Department of Chemistry, Baoji College of Arts. & Sci., Baoji 721013, China;3. College of Chemical Engineering, Lanzhou University of Arts and Science, Lanzhou 730010, China;1. Key Laboratory of Cluster Science of Ministry of Education, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China;2. School of Food Science and Technology & School of Chemical Engineering, Hubei University of Arts and Science, Xiangyang 441053, Hubei Province, China |
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| Abstract: | A series of polymer donor materials 1-5 based on diketopyrrolopyrrole and thiophene unit which have been widely used in organic solar cells (OSCs) were investigated based on quantum chemical calculations. The effect of fluorine and cyano substitutions in polymer donor materials was focused on. Based on the investigation on electronic structures and optical properties of the reported molecules 1 and 2 and the analysis on some parameters relevant to charge dissociation ability at donor/acceptor interface constituted by 1 and 2 with PC61BM such as intermolecular charge transfer and recombination, driving force and Coulombic bound energy, we explained why fluorine substitution can improve OPV efficiency through strengthening eletron-withdrawing ability from a theoretical perspective. Then we designed cyano-substituted polymers 3-5 with the aim of obtaining better photovoltaic donor materials. The results reveal that our attempt to design donor materials which can balance large open-circuit voltage (Voc) and high short-circuit current (Jsc) in OSCs has worked out. It is worth noting that the substitutions of fluorine and cyano groups synergistically reduce energy gap and HOMO energy level of polymers 3 and 4. Moreover, 3/PC61BM and 4/PC61BM heterojunctions show over 107 and 104 times higher than 1/PC61BM on the ratios of intermolecular charge transfer and recombination rates (kinter-CT/kinter-CR). Thus, our work here may provide an efficient strategy to design promising donor materials in OPVs and we hope it could be useful in the future experimental synthesis. |
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| Keywords: | Organic solar cells Polymer donor Fluorination Cyanation Charge transfer at interface DFT |
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