Kobryn Alexander E, Gusarov Sergey, Shankar Karthik
National Institute for Nanotechnology, National Research Council Canada, 11421 Saskatchewan Drive, Edmonton, AB T6G 2M9, Canada.
Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB T6G 2V4, Canada.
Polymers (Basel). 2016 Apr 9;8(4):136. doi: 10.3390/polym8040136.
Although better means to model the properties of bulk heterojunction molecular blends are much needed in the field of organic optoelectronics, only a small subset of methods based on molecular dynamics- and Monte Carlo-based approaches have been hitherto employed to guide or replace empirical characterization and testing. Here, we present the first use of the integral equation theory of molecular liquids in modelling the structural properties of blends of phenyl-C-butyric acid methyl ester (PCBM) with poly(3-hexylthiophene) (P3HT) and a carboxylated poly(3-butylthiophene) (P3BT), respectively. For this, we use the Reference Interaction Site Model (RISM) with the Universal Force Field (UFF) to compute the microscopic structure of blends and obtain insight into the miscibility of its components. Input parameters for RISM, such as optimized molecular geometries and charge distribution of interaction sites, are derived by the Density Functional Theory (DFT) methods. We also run Molecular Dynamics (MD) simulation to compare the diffusivity of the PCBM in binary blends with P3HT and P3BT, respectively. A remarkably good agreement with available experimental data and results of alternative modelling/simulation is observed for PCBM in the P3HT system. We interpret this as a step in the validation of the use of our approach for organic photovoltaics and support of its results for new systems that do not have reference data for comparison or calibration. In particular, for the less-studied P3BT, our results show that expectations about its performance in binary blends with PCBM may be overestimated, as it does not demonstrate the required level of miscibility and short-range structural organization. In addition, the simulated mobility of PCBM in P3BT is somewhat higher than what is expected for polymer blends and falls into a range typical for fluids. The significance of our predictive multi-scale modelling lies in the insights it offers into nanoscale morphology and charge transport behaviour in multi-component organic semiconductor blends.
尽管有机光电子领域迫切需要更好的方法来模拟本体异质结分子共混物的性质，但迄今为止，基于分子动力学和蒙特卡罗方法的方法中，只有一小部分被用于指导或取代经验表征和测试。在此，我们首次使用分子液体的积分方程理论，分别对苯基-C-丁酸甲酯（PCBM）与聚（3-己基噻吩）（P3HT）以及羧基化聚（3-丁基噻吩）（P3BT）的共混物的结构性质进行建模。为此，我们使用具有通用力场（UFF）的参考相互作用位点模型（RISM）来计算共混物的微观结构，并深入了解其组分的混溶性。RISM的输入参数，如优化的分子几何结构和相互作用位点的电荷分布，是通过密度泛函理论（DFT）方法推导出来的。我们还进行了分子动力学（MD）模拟，以比较PCBM在分别与P3HT和P3BT形成的二元共混物中的扩散率。对于P3HT体系中的PCBM，观察到与现有实验数据以及替代建模/模拟结果有非常好的一致性。我们将此视为验证我们的方法用于有机光伏的一个步骤，并支持其对于没有参考数据进行比较或校准的新体系的结果。特别是，对于研究较少的P3BT，我们的结果表明，对其与PCBM形成二元共混物时性能的预期可能被高估了，因为它没有表现出所需的混溶水平和短程结构组织。此外，PCBM在P3BT中的模拟迁移率略高于聚合物共混物的预期值，且处于流体的典型范围内。我们的预测性多尺度建模的意义在于它对多组分有机半导体共混物中的纳米级形态和电荷传输行为提供了深入见解。
