Muth Dominik, Anhäuser Sebastian, Bischof Daniel, Krüger Anton, Witte Gregor, Gerhard Marina
Department of Physics and Material Sciences Center, Semiconductor Spectroscopy Group, Philipps-Universität Marburg, Renthof 7a, 35032 Marburg, Germany.
Department of Physics and Material Sciences Center, Molecular Solids Group, Philipps-Universität Marburg, Renthof 7, 35032 Marburg, Germany.
Nanoscale. 2024 Jul 18;16(28):13471-13482. doi: 10.1039/d4nr01086h.
Efficient exciton migration is crucial for optoelectronic organic devices. While the transport of triplet excitons is generally slow compared to singlet excitons, triplet exciton migration in certain molecular semiconductors with endothermic singlet fission appears to be enhanced by a time-delayed regeneration of the more mobile singlet species triplet fusion. This combined transport mechanism could be exploited for devices, but the interplay between singlet fission and triplet fusion, as well as the role of trap states is not yet well understood. Here, we study the spatiotemporal exciton dynamics in the singlet fission material tetracene by means of time resolved photoluminescence micro-spectroscopy on crystalline samples of different quality. Varying the temperature allows us to modify the dynamic equilibrium between singlet, triplet and trapped excitons. Supported by a kinetic model, we find that thermally activated dissociation of triplet pairs into free triplet excitons can account for an increase of the diffusion length below room temperature. Moreover, we demonstrate that trapping competes efficiently with exciton migration.
高效的激子迁移对于光电子有机器件至关重要。虽然与单线态激子相比，三线态激子的传输通常较慢，但在某些具有吸热单线态裂变的分子半导体中，三线态激子迁移似乎通过更易移动的单线态物种三线态融合的时间延迟再生而得到增强。这种组合的传输机制可用于器件，但单线态裂变和三线态融合之间的相互作用以及陷阱态的作用尚未得到很好的理解。在这里，我们通过对不同质量的晶体样品进行时间分辨光致发光显微光谱研究了单线态裂变材料并四苯中的时空激子动力学。改变温度使我们能够改变单线态、三线态和捕获激子之间的动态平衡。在动力学模型的支持下，我们发现三线态对热激活解离为自由三线态激子可以解释室温以下扩散长度的增加。此外，我们证明捕获与激子迁移有效竞争。
