First principles modeling of exciton-polaritons in polydiacetylene chains
First principles modeling of exciton-polaritons in polydiacetylene chains
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DOI：
10.1063/5.0019009
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发表时间：
2020-08-28
影响因子：
4.4
通讯作者：
Beljonne, David
中科院分区：
文献类型：
--
作者：
Alvertis, Antonios M.;Pandya, Raj;Beljonne, David
有机材料中的激子-极化子是光子和束缚激子强相互作用的混合态。有机极化子对光电子学的应用有着极大的兴趣；然而，由于缺乏第一原理方法来量化这些系统中的光-物质相互作用，从而可以制定分子设计规则，这阻碍了这一目标的进展。在这里，我们提出了一个理论框架，它将激子的第一性原理计算与经典电动力学相结合，以量化光与物质的相互作用。我们通过研究共轭聚合物聚二乙炔的变体来举例说明我们的方法，我们证明了大的聚合物共轭长度对于强激子-光子耦合是关键的，因此潜在的没有静态无序的纯结构的重要性。通过与我们的实验反射率测量进行比较，我们发现激子与振动的耦合，表现为吸收中的声子边带，在一定的频率范围内对光-物质耦合的大小有强烈的影响。我们的方法为更深入地理解有机材料中的极化子开辟了道路，我们强调，对激子-光子相互作用的定量准确计算将需要自我一致地解释所有无序源。
Exciton-polaritons in organic materials are hybrid states that result from the strong interaction of photons and the bound excitons that these materials host. Organic polaritons hold great interest for optoelectronic applications; however, progress toward this end has been impeded by the lack of a first principles approach that quantifies light-matter interactions in these systems, which would allow the formulation of molecular design rules. Here, we present a theoretical framework that combines first principles calculations for excitons with classical electrodynamics in order to quantify light-matter interactions. We exemplify our approach by studying variants of the conjugated polymer polydiacetylene, and we show that a large polymer conjugation length is critical toward strong exciton-photon coupling, hence underlying the importance of pure structures without static disorder. By comparing to our experimental reflectivity measurements, we show that the coupling of excitons to vibrations, manifested by phonon side bands in the absorption, has a strong impact on the magnitude of light-matter coupling over a range of frequencies. Our approach opens the way toward a deeper understanding of polaritons in organic materials, and we highlight that a quantitatively accurate calculation of the exciton-photon interaction would require accounting for all sources of disorder self-consistently.