Wave Function Based Analysis of Dynamics versus Yield of Free Triplets in Intramolecular Singlet Fission
Wave Function Based Analysis of Dynamics versus Yield of Free Triplets in Intramolecular Singlet Fission
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DOI：
10.1021/acs.jpca.0c07938
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发表时间：
2020-12-10
影响因子：
2.9
通讯作者：
Mazumdar, Sumit
中科院分区：
文献类型：
--
作者：
Chesler, Rafi;Khan, Souratosh;Mazumdar, Sumit
在几种分子内单重态裂变材料中的实验表明，三重态-三重态自旋双激子的寿命比人们一直认为的要长得多，这开启了一种损失机制，可以在双激子解离为自由三重态之前将其湮灭。为了更好地理解作为潜在的单重态裂变候选者而研究的大烯二聚体的连接体依赖的行为，我们对假想的苯环连接的菲分子的激发态波函数进行了多体计算。计算揭示了我们没有预料到的特征，我们发现这些特征延续到了真正的共价连接的并五苯二聚体。在烯二聚体中，相关的三重-三重自旋双激子的解离和自由三重态的产生可能是困难的，其中三重-三重自旋双激子的形成是真正超快的。相反，相对较慢的双激子形成可能意味着较小的自旋双激子结合能和较大的自由三重态产额。目前可用的实验结果似乎支持这一结论。这两种不同的行为是否是从光学单重态产生三重态-三重态的不同机制的结果，这是一个有趣的理论问题。
Experiments in several intramolecular singlet fission materials have indicated that the triplet-triplet spin biexciton has a much longer lifetime than believed until recently, opening up loss mechanisms that can annihilate the biexciton prior to its dissociation to free triplets. We have performed many-body calculations of excited state wave functions of hypothetical phenylene-linked anthracene molecules to better understand linker-dependent behavior of dimers of larger acenes being investigated as potential singlet fission candidates. The calculations reveal unanticipated features that we show carry over to the real covalently linked pentacene dimers. Dissociation of the correlated triplet-triplet spin biexciton and free triplet generation may be difficult in acene dimers where the formation of the triplet-triplet spin biexciton is truly ultrafast. Conversely, relatively slower biexciton formation may indicate smaller spin biexciton binding energy and greater yield of free triplets. Currently available experimental results appear to support this conclusion. Whether or not the two distinct behaviors are consequences of distinct mechanisms of triplet-triplet generation from the optical singlet is an interesting theoretical question.