Impact of non-equilibrium molecular packings on singlet fission in microcrystals observed using 2D white-light microscopy
Impact of non-equilibrium molecular packings on singlet fission in microcrystals observed using 2D white-light microscopy
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DOI：
10.1038/s41557-019-0368-9
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发表时间：
2020-01-01
期刊：
影响因子：
21.8
通讯作者：
Zanni, Martin T.
中科院分区：
文献类型：
--
作者：
Jones, Andrew C.;Kearns, Nicholas M.;Zanni, Martin T.
单线态裂变，将一个单线态激子分裂成两个三重态激子的过程，被认为是提高未来光伏器件效率的一种机制。在单线态裂变的有机半导体中，分子间的几何关系通过设置分子间耦合来决定系统的能量学，起着重要的作用。在这里，我们使用超快二维白光显微镜对tips -并五苯微晶体进行空间成像，发现在微晶体中稀疏分布着低能单重态，在边缘和形态缺陷处浓度较高。这些单重态的光谱与滑动堆积的分子几何形状和增加的电荷转移耦合一致。这些低能单重态的皮秒时间尺度动力学与相关的三重态相匹配，我们将其归因于这些位点的单重态/三重态相互转换。我们的观察结果支持这样的结论，即具有有利能量学的小几何种群可以在单线态裂变过程中发挥巨大的作用。
Singlet fission, the process of splitting a singlet exciton into two triplet excitons, has been proposed as a mechanism for improving the efficiency of future photovoltaic devices. In organic semiconductors exhibiting singlet fission, the geometric relationship between molecules plays an important role by setting the intermolecular couplings that determine the system energetics. Here, we spatially image TIPS-pentacene microcrystals using ultrafast two-dimensional white-light microscopy and discover a low-energy singlet state sparsely distributed throughout the microcrystals, with higher concentrations at edges and morphological defects. The spectra of these singlet states are consistent with slip-stacked molecular geometries and increased charge-transfer couplings. The picosecond-timescale kinetics of these low-energy singlet states matches that of the correlated triplet-pair state, which we attribute to singlet/triplet-pair interconversion at these sites. Our observations support the conclusion that small populations of geometries with favourable energetics can play outsized roles in singlet fission processes.