Centre Énergie Matériaux Télécommunications, Institut National de la Recherche Scientifique, 1650 boulevard Lionel-Boulet, Varennes QC J3X1S2, Canada.
Molecules. 2020 May 9;25(9):2233. doi: 10.3390/molecules25092233.
Development of new functional materials for novel energy conversion and storage technologies is often assisted by ab initio modeling. Specifically, for organic materials, such as electron and hole transport materials for perovskite solar cells, LED (light emitting diodes) emitters for organic LEDs (OLEDs), and active electrode materials for organic batteries, such modeling is often done at the molecular level. Modeling of aggregate-state effects is onerous, as packing may not be known or large simulation cells may be required for amorphous materials. Yet aggregate-state effects are essential to estimate charge transport rates, and they may also have substantial effects on redox potentials (voltages) and optical properties. This paper summarizes recent studies by the author's group of aggregation effects on the electronic properties of organic materials used in optoelectronic devices and in organic batteries. We show that in some cases it is possible to understand the mechanism and predict specific performance characteristics based on simple molecular models, while in other cases the inclusion of effects of aggregation is essential. For example, it is possible to understand the mechanism and predict the overall shape of the voltage-capacity curve for insertion-type organic battery materials, but not the absolute voltage. On the other hand, oligomeric models of -type organic electrode materials can allow for relatively reliable estimates of voltages. Inclusion of aggregate state modeling is critically important for estimating charge transport rates in materials and interfaces used in optoelectronic devices or when intermolecular charge transfer bands are important. We highlight the use of the semi-empirical DFTB (density functional tight binding) method to simplify such calculations.
开发用于新型能量转换和存储技术的新型功能材料通常需要借助从头算建模。具体来说，对于有机材料，例如钙钛矿太阳能电池的电子和空穴传输材料、有机发光二极管 (OLED) 的 LED (发光二极管) 发射器以及有机电池的活性电极材料，通常在分子水平上进行建模。聚合态效应的建模很繁琐，因为可能不知道堆积方式，或者对于非晶材料可能需要大的模拟单元。然而，聚合态效应对于估计电荷传输速率至关重要，它们也可能对氧化还原电位 (电压) 和光学性质产生重大影响。本文总结了作者小组最近对用于光电设备和有机电池的有机材料的聚合效应对电子性质影响的研究。我们表明，在某些情况下，基于简单的分子模型可以理解机制并预测特定的性能特征，而在其他情况下，聚合效应的包含是必不可少的。例如，对于插入型有机电池材料，可以理解机制并预测电压-容量曲线的整体形状，但不能预测绝对电压。另一方面，-型有机电极材料的低聚物模型可以允许对电压进行相对可靠的估计。聚合态建模的包含对于估计光电设备中使用的材料和界面中的电荷传输速率以及当分子间电荷转移带很重要时至关重要。我们强调了使用半经验 DFTB (密度泛函紧束缚) 方法来简化这些计算。
