Triplet harvesting in the polaritonic regime: A variational polaron approach
Triplet harvesting in the polaritonic regime: A variational polaron approach
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DOI：
10.1063/1.5100192
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发表时间：
2019-08-07
影响因子：
4.4
通讯作者：
Yuen-Zhou, Joel
中科院分区：
文献类型：
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作者：
Martinez-Martinez, Luis A.;Eizner, Elad;Yuen-Zhou, Joel
我们探讨了一个量子力学模型的电致发光效率的大量分子发射器嵌入在一个光学微腔。我们的特点的情况下，微腔增强收获的三重态激子通过反向系统间穿越（R-ISC）到单重态人口，可以发光。为此，我们开发了一个时间局部主方程在变分优化的框架，它允许探索的人口动态的化学相关的物种在不同制度的发射耦合到凝聚相振动浴和微腔光子模式。对于比R-ISC更快平衡的振动浴（在具有弱单重态-三重态混合的发射体中），我们的结果表明，对于单重态激子到光子模的强耦合，只要单重态到三重态激子的跃迁在反转Marcus区域内，就可以获得相对于无腔对应物的效率的显著改善;在这些情况下，相对于从三重态到单重态激子的活化能势垒，从三重态到较低极化激元的活化能势垒可以大大降低，从而克服了极化激元状态在宏观数量的分子上的有害离域。另一方面，对于平衡慢于R-ISC的振动浴（即，具有强的单重态-三重态混合的发射体），我们发现，虽然可以通过振动弛豫到极化激元中来获得光致发光的增强，但是这仅发生在耦合到光子模式的少量发射体上，并且极化激元在许多发射体上的离域最终对电致发光效率是有害的。这些发现提供了深入了解由于弱和强的光物质耦合在分子材料中的光电过程的可调谐性。由AIP Publishing授权出版。
We explore the electroluminescence efficiency for a quantum mechanical model of a large number of molecular emitters embedded in an optical microcavity. We characterize the circumstances under which a microcavity enhances harvesting of triplet excitons via reverse intersystem-crossing (R-ISC) into singlet populations that can emit light. For that end, we develop a time-local master equation in a variationally optimized frame, which allows for the exploration of the population dynamics of chemically relevant species in different regimes of emitter coupling to the condensed phase vibrational bath and to the microcavity photonic mode. For a vibrational bath that equilibrates faster than R-ISC (in emitters with weak singlet-triplet mixing), our results reveal that significant improvements in efficiencies with respect to the cavity-free counterpart can be obtained for strong coupling of the singlet exciton to a photonic mode, as long as the singlet to triplet exciton transition is within the inverted Marcus regime; under these circumstances, the activation energy barrier from the triplet to the lower polariton can be greatly reduced with respect to that from the triplet to the singlet exciton, thus overcoming the detrimental delocalization of the polariton states across a macroscopic number of molecules. On the other hand, for a vibrational bath that equilibrates slower than R-ISC (i.e., emitters with strong singlet-triplet mixing), we find that while enhancements in photoluminescence can be obtained via vibrational relaxation into polaritons, this only occurs for a small number of emitters coupled to the photon mode, with delocalization of the polaritons across many emitters eventually being detrimental to electroluminescence efficiency. These findings provide insight into the tunability of optoelectronic processes in molecular materials due to weak and strong light-matter coupling. Published under license by AIP Publishing.