Quantifying Exciton Transport in Singlet Fission Diblock Copolymers
Quantifying Exciton Transport in Singlet Fission Diblock Copolymers
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DOI：
10.1021/jacs.1c13456
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发表时间：
2022-02-23
影响因子：
15
通讯作者：
Sfeir, Matthew Y.
中科院分区：
文献类型：
--
作者：
He, Guiying;Yablon, Lauren M.;Sfeir, Matthew Y.
单线态裂变（SF）是有机发色团中激子倍增的机制，具有驱动高效光电器件的潜力。创建由SF操作的有效器件架构关键取决于跨多个长度尺度的电子相互作用——从单个分子到生色团间相互作用，促进多激子相移和激子向供体-受体界面扩散。因此，必须了解多发色团系统中多激子传输和界面能量转移的基础。有趣的是，嵌段共聚物（BCP）可以通过调整结构单元的性质来设计来控制多尺度相互作用，但这些大分子中的SF动力学尚不清楚。在这里，我们设计了二嵌段共聚物，该共聚物在具有悬挂并五苯发色团的嵌段和具有悬挂并四苯发色团的附加嵌段之间的界面处包含固有能量裂缝。两个嵌段之间的单线态和三线态能量偏移产生了激子在稀溶液中沿着BCP链传输的驱动力。使用时间分辨光谱，我们量化了关键能量转移步骤的产率，包括并五苯-并四苯界面上的单线态和三线态能量转移过程。从这个模块化 BCP 架构中，我们将能量传输时间尺度和相对产量与每个块的长度相关联。量化这些能量转移过程的能力为了解块状晶体系统和小分子二聚体之间临界长度尺度的激子传输提供了宝贵的见解，而小分子二聚体是一个尚未充分探索的领域。
Singlet fission (SF) is a mechanism of exciton multiplication in organic chromophores, which has potential to drive highly efficient optoelectronic devices. Creating effective device architectures that operate by SF critically depends on electronic interactions across multiple length scales-from individual molecules to interchromophore interactions that facilitate multiexciton dephasing and exciton diffusion toward donor-acceptor interfaces. Therefore, it is imperative to understand the underpinnings of multiexciton transport and interfacial energy transfer in multichromophore systems. Interestingly, block copolymers (BCPs) can be designed to control multiscale interactions by tailoring the nature of the building blocks, yet SF dynamics are not well understood in these macromolecules. Here, we designed diblock copolymers comprising an inherent energy cleft at the interface between a block with pendent pentacene chromophores and an additional block with pendent tetracene chromophores. The singlet and triplet energy offset between the two blocks creates a driving force for exciton transport along the BCP chain in dilute solution. Using time-resolved optical spectroscopy, we have quantified the yields of key energy transfer steps, including both singlet and triplet energy transfer processes across the pentacene-tetracene interface. From this modular BCP architecture, we correlate the energy transfer time scales and relative yields with the length of each block. The ability to quantify these energy transfer processes provides valuable insights into exciton transport at critical length scales between bulk crystalline systems and small-molecule dimers-an area that has been underexplored.