Zhao Zhi-Wen, Pan Qing-Qing, Li Shuang-Bao, Duan Yu-Ai, Geng Yun, Zhang Min, Su Zhong-Min
Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Chang Chun, 130024, Jilin, PR China.
Department of Chemistry, Capital Normal University, Beijing, 100048, PR China.
J Mol Graph Model. 2017 Oct;77:9-16. doi: 10.1016/j.jmgm.2017.07.027. Epub 2017 Aug 2.
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 PCBM 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 (V) and high short-circuit current (J) 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/PCBM and 4/PCBM heterojunctions show over 10 and 10 times higher than 1/PCBM on the ratios of intermolecular charge transfer and recombination rates (k/k). 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.
基于量子化学计算，研究了一系列基于二酮吡咯并吡咯和噻吩单元的聚合物供体材料1-5，这些材料已广泛应用于有机太阳能电池（OSC）中。重点关注了聚合物供体材料中氟和氰基取代的影响。通过对已报道分子1和2的电子结构和光学性质的研究，以及对由1和2与PCBM构成的供体/受体界面处与电荷解离能力相关的一些参数（如分子间电荷转移和复合、驱动力和库仑束缚能）的分析，我们从理论角度解释了氟取代为何能通过增强吸电子能力来提高有机光伏（OPV）效率。然后，我们设计了氰基取代的聚合物3-5，旨在获得更好的光伏供体材料。结果表明，我们设计能够平衡有机太阳能电池中大开路电压（V）和高短路电流（J）的供体材料的尝试取得了成功。值得注意的是，氟和氰基的取代协同降低了聚合物3和4的能隙和最高占据分子轨道（HOMO）能级。此外，3/PCBM和4/PCBM异质结在分子间电荷转移和复合率之比（k/k）上比1/PCBM高出10倍和10倍以上。因此，我们在此的工作可能为设计有前景的有机光伏供体材料提供一种有效策略，我们希望它在未来的实验合成中有用。
