Singlet Exciton Diffusion in Organic Crystals Based on Marcus Transfer Rates.
Singlet Exciton Diffusion in Organic Crystals Based on Marcus Transfer Rates.
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DOI：
10.1021/ct500014h
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发表时间：
2014-02
影响因子：
5.5
通讯作者：
V. Stehr;R. Fink;B. Engels;J. Pflaum;C. Deibel
中科院分区：
文献类型：
--
作者：
V. Stehr;R. Fink;B. Engels;J. Pflaum;C. Deibel
激子扩散是光电子器件能量转换的关键步骤。这催生了期望的理论方法，允许快速但可靠的测定材料依赖的激子输运参数。为此，马库斯理论，这是广泛使用的背景下的电荷传输，适用于激子扩散。与通过耦合和光谱重叠计算激子跳跃速率的常见方法相比，这种替代方法成本较低，因为仅需要重组能而不是光谱重叠。为了证明该方法的能力，计算了萘、蒽和二茚并萘晶体的扩散常数，并与使用公认的激子跳跃率（包括耦合和光谱重叠）进行的计算以及实验数据进行了比较。这些测试计算表明，基于马库斯的激子扩散性质往往太小，但定性正确（即，它们似乎有助于预测趋势）。然而，为了得到可靠的结果，需要高水平的量子化学方法来计算重组能。但是，它们只需要计算一次。所有单体对所需的偶联常数具有相当小的影响，即，它们可以通过较低级别的方法来计算，这使得该方法的成本更低。
Exciton diffusion is a critical step for energy conversion in optoelectronic devices. This spawns the desire for theoretical approaches that allow for fast but reliable determinations of the material-dependent exciton transport parameters. For this purpose, the Marcus theory, which is widely used in the context of charge transport, is adapted to exciton diffusion. In contrast to the common approach of calculating the exciton hopping rate via the coupling and the spectral overlap, this alternative approach is less costly, because, instead of the spectral overlap, only the reorganization energy is needed. To demonstrate the capability of the approach, the diffusion constants for naphthalene, anthracene, and diindenoperylene crystals are calculated and compared with both calculations conducted with the well-established exciton hopping rate, including coupling and spectral overlap, and with experimental data. These test calculations show that Marcus-based exciton diffusion properties tend to be too small but are qualitatively correct (i.e., they seem to be useful to predict trends). Nevertheless, for reliable results, high-level quantum chemical approaches are necessary for the computation of the reorganization energies. However, they have to be calculated only once. Coupling constants, which are needed for all pairs of monomers, have a considerably smaller influence, i.e., they can be computed by a lower level approach, which makes the method even less costly.