Petascale Simulations of the Morphology and the Molecular Interface of Bulk Heterojunctions
Petascale Simulations of the Morphology and the Molecular Interface of Bulk Heterojunctions
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DOI：
10.1021/acsnano.6b03009
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发表时间：
2016-07-01
期刊：
影响因子：
17.1
通讯作者：
Kilbey, S. Michael, II
中科院分区：
文献类型：
--
作者：
Carrillo, Jan-Michael Y.;Seibers, Zach;Kilbey, S. Michael, II
了解添加剂如何在体异质结（BHJ）薄膜内相互作用和分离，对于在多个长度尺度上控制结构并改善光伏性能至关重要。聚（3-己基噻吩）（P3 HT）和苯基-C-61-丁酸甲酯（PCBM）的共混物，是相称的BHJ薄膜的大小的形态演变研究使用千万亿次粗粒度的分子动力学模拟。两种组分和三种组分的系统之间的比较，含有短的P3 HT链作为添加剂进行热退火表明，短链改变的形态，显然是有用的方式：他们有效地迁移到P3 HT/PCBM界面，增加P3 HT域的大小和界面面积。模拟结果同意从中子反射测量，揭示PCBM富集基板和空气界面附近，但减少PCBM富集时，少量的短P3 HT链集成到BHJ混合物的深度剖面。P3 HT/PCBM共混物界面的原子模拟显示界面厚度作为低聚P3 HT添加剂中的重复单元数的函数的非单调依赖性，并且噻吩环在它们接近PCBM域时平行于界面平面取向。使用纳米级的几何形状的P3 HT低聚物，LUMO和HOMO能级计算的密度泛函理论被发现是不变的整个供体/受体界面。在所有长度尺度下添加剂、加工和形态之间的这些联系通常可用于改善器件性能的努力。
Understanding how additives interact and segregate within bulk heterojunction (BHJ) thin films is critical for exercising control over structure at multiple length scales and delivering improvements in photovoltaic performance. The morphological evolution of poly(3-hexylthiophene) (P3HT) and phenyl-C-61- butyric acid methyl ester (PCBM) blends that are commensurate with the size of a BHJ thin film is examined using petascale coarse-grained molecular dynamics simulations. Comparisons between two-component and three-component systems containing short P3HT chains as additives undergoing thermal annealing demonstrate that the short chains alter the morphology in apparently useful ways: they efficiently migrate to the P3HT/PCBM interface, increasing the P3HT domain size and interfacial area. Simulation results agree with depth profiles determined from neutron reflectometry measurements that reveal PCBM enrichment near substrate and air interfaces but a decrease in that PCBM enrichment when a small amount of short P3HT chains are integrated into the BHJ blend. Atomistic simulations of the P3HT/PCBM blend interfaces show a nonmonotonic dependence of the interfacial thickness as a function of number of repeat units in the oligomeric P3HT additive, and the thiophene rings orient parallel to the interfacial plane as they approach the PCBM domain. Using the nanoscale geometries of the P3HT oligomers, LUMO and HOMO energy levels calculated by density functional theory are found to be invariant across the donor/acceptor interface. These connections between additives, processing, and morphology at all length scales are generally useful for efforts to improve device performance.