Solvent-Dependent Structure Formation in Drying P3HT:PCBM Films Studied by Molecular Dynamics Simulations
Solvent-Dependent Structure Formation in Drying P3HT:PCBM Films Studied by Molecular Dynamics Simulations
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DOI：
10.1002/mats.201600075
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发表时间：
2016-11-01
影响因子：
1.4
通讯作者：
Bobbert, Peter
中科院分区：
文献类型：
--
作者：
Negi, Vikas;Lyulin, Alexey;Bobbert, Peter
采用粗粒化分子动力学模拟方法研究了给体-受体共混体系聚（3-己基噻吩-2，5-二基）：[6，6]-苯基-C61-丁酸甲酯（P3 HT：PCBM）在溶剂蒸发过程中的相分离.为此，将平衡的P3 HT：PCBM：溶剂混合物置于细长的模拟箱中，之后以规则的时间间隔从膜上方的区域去除溶剂分子。三种常用的溶剂被认为是：氯仿（CFM），氯苯（CLB）和邻二氯苯（oDCB）。粗粒度的溶剂-溶剂相互作用参数进行调整，以重现大气沸点温度，而PCBM-溶剂相互作用参数进行调整，以重现PCBM的溶解度。其他参数取自文献。在蒸发过程中，观察到形成耗尽溶剂的结壳，其中发生P3 HT和PCBM的聚集。与实验结果一致，对于CLB和oDCB，干膜的顶部区域富含PCBM，对于CFM，干膜的顶部区域富含P3 HT，而干膜的最顶层总是富含P3 HT。这种垂直分离归因于P3 HT由于其低表面能而移动到表面的趋势与PCBM根据其溶解度被蒸发溶剂沿着拖到表面的不同趋势之间的竞争。此外，与实验一致，P3 HT-PCBM的界面面积大于CLB和oDCB的CFM。对于CLB和oDCB，发现从顶部和底部表面开始的失稳P3 HT-PCBM分解的指示，而对于CFM，相分离似乎在膜的本体中开始。
Phase separation in the donor-acceptor blend poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) during evaporation of a solvent using coarse-grained molecular dynamics simulations is studied here. To this end, an equilibrated P3HT:PCBM:solvent mixture is placed in an elongated simulation box, after which solvent molecules are removed at regular time intervals from a region above the film. Three often-used solvents are considered:chloroform (CFM), chlorobenzene (CLB), and orthodichlorobenzene (oDCB). The coarse-grained solvent-solvent interaction parameters are tuned to reproduce the atmospheric boiling temperatures, while the PCBM-solvent interaction parameters are tuned to reproduce the PCBM solubilities. Other parameters are taken from the literature. During evaporation, the formation of a crust that is depleted of solvent, in which aggregation of P3HT and PCBM occurs, is observed. In agreement with experiment, the top region of the dry film is rich in PCBM for the cases of CLB and oDCB, and rich in P3HT for the case of CFM, while the very top layer of the film is always rich in P3HT. This vertical separation is ascribed to a competition between the tendency of P3HT to move to the surface due to its low surface energy and the different tendencies of PCBM to be dragged along to the surface by the evaporating solvent depending on its solubility. Also in agreement with experiment, the P3HT-PCBM interface area is larger for CLB and oDCB than for CFM. For CLB and oDCB, an indication for a spinodal P3HT-PCBM decomposition starting from the top and bottom surface is found, whereas for CFM the phase separation appears to be initiated in the bulk of the film.