Molecular Packing Determines Singlet Exciton Fission in Organic Semiconductors
Molecular Packing Determines Singlet Exciton Fission in Organic Semiconductors
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DOI：
10.1021/nn502544d
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发表时间：
2014-07-01
期刊：
影响因子：
17.1
通讯作者：
Chatterjee, Sangam
中科院分区：
文献类型：
--
作者：
Kolata, Kolja;Breuer, Tobias;Chatterjee, Sangam
通过单线态激子裂变的载流子倍增增强有机固体中的光伏转换效率。一个单重态激子衰变为两个三重态，每个光子可以提取两个电子，因此有望克服肖克利-奎塞尔极限。然而，单重态激子裂变的微观机理，特别是分子堆积与电子响应的关系仍不清楚，这阻碍了有机光伏器件的系统改进。对于模型体系全氟并五苯，我们的实验表明，单重态激子裂变大大增强了滑移堆叠分子排列，通过寻址不同的晶轴具有不同的包装方案。这表明裂变过程强烈依赖于分子间的耦合：滑移堆积有利于激发的离域，并允许有效的激子裂变，而常见的人字形分子堆积模式中的面到边的分子取向甚至抑制了它。此外，我们澄清了有争议的争论的准分子态的中介作用，而不是竞争性或间接性。我们的详细研究结果可作为指导下一代分子材料的设计，应用于未来的有机光捕获器件利用单重态激子裂变。
Carrier multiplication by singlet exciton fission enhances photovoltaic conversion efficiencies in organic solids. This decay of one singlet exciton into two triplet states allows the extraction of up to two electrons per harvested photon and, hence, promises to overcome the Shockley-Queisser limit. However, the microscopic mechanism of singlet exciton fission, especially the relation between molecular packing and electronic response, remains unclear, which therefore hampers the systematic improvement of organic photovoltaic device. For the model system perfluoropentacene, we experimentally show that singlet exciton fission Is greatly enhanced for a slip-stacked molecular arrangement by addressing different crystal axis featuring different packing scheme. This reveals that the fission process strongly depends on the intermolecular coupling: slip-stacking favors delocalization of excitations and allows for efficient exciton fission, while face-to-edge molecular orientations commonly found in the prevailing herringbone molecular stacking patterns even suppress it. Furthermore, we clarify the controversially debated role of excimer states as intermediary rather than competitive or precursory. Our detailed findings serve as a guideline for the deign of next-generation molecular materials for application in future organic light-harvesting device exploiting singlet exciton fission.