Exciton–plasmon polaritons have gained increasing interest over recent years due to their versatile properties emerging by the underlying light–matter coupling and making them potential candidates for new photonic applications. We have advanced this concept by studying thin films of laterally aligned J-aggregates of self-assembled tetra-bay phenoxy-dendronized perylene bisimide (PBI) molecules, arranged in a helical manner of three slip-stacked strands on a silver surface. As a result of the interaction between the uniformly aligned dipole moments and the surface plasmons of a thin silver layer underneath, the excitonic state at 1.94 eV evolves into dispersions in absorption and emission, both characterized by distinct anisotropy. The coupling constant defined by the scalar product of the transition dipole moment μ⃗ and the surface plasmon wavevector k⃗_x shows a pronounced 2-fold rotational symmetry with values between almost 0 and 29.5 meV. Complementary time-dependent density functional theory (TD-DFT) calculations of the angular-dependent absorption and photoluminescence (PL) provide insights in the coherent energy exchange between the excitonic and plasmonic subsystems. Additionally, power-dependent PL studies yield first evidence that the diffusion length of the coupled exciton–plasmon polaritons exceeds that of the mere Frenkel state in neat PBI-based J-aggregates by at least 1 order of magnitude. Our results not only demonstrate the possibility to control the photophysical properties of strongly coupled states by their spatially anisotropic light–matter interaction but also reveal innovative strategies to influence optoelectronic device operation by the directional transport of hybrid-state energy.

中文翻译：

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强耦合金属-有机薄膜中 Plexcion 的各向异性光物理性质


激子-等离激元极化激元近年来越来越受到关注，因为它们的通用特性是由潜在的光-物质耦合出现的，并使其成为新光子应用的潜在候选者。我们通过研究自组装的四湾苯氧基树膦化苝双酰亚胺 （PBI） 分子的横向排列 J 聚集体的薄膜来推进这一概念，这些分子以螺旋方式排列在银表面上的三条滑叠链。由于均匀排列的偶极矩与下方薄银层的表面等离激元之间的相互作用，1.94 eV 的激子态演变为吸收和发射的色散，两者均具有明显的各向异性特征。由过渡偶极矩 μ⃗ 和表面等离子体波矢 k⃗_x 的标量乘积定义的耦合常数显示出明显的 2 倍旋转对称性，值几乎在 0 到 29.5 meV 之间。角度相关吸收和光致发光 （PL） 的互补时间依赖密度泛函理论 （TD-DFT） 计算为激发子和等离激元子系统之间的相干能量交换提供了见解。此外，功率依赖性 PL 研究提供了第一个证据，即耦合激子-等离激元极化激元的扩散长度至少比基于 PBI 的整洁 J 聚集体中的单纯 Frenkel 态的扩散长度高出 1 个数量级。我们的结果不仅证明了通过空间各向异性光-物质相互作用来控制强耦合态的光物理特性的可能性，而且还揭示了通过混合态能量的定向传输来影响光电器件运行的创新策略。