Sousa C, Sánchez-Mansilla A, Broer R, Straatsma T P, de Graaf C
Departament de Ciència de Materials i Química Física and Institut de Química Teòrica i Computacional, Universitat de Barcelona, 08028 Barcelona, Spain.
Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, 43007 Tarragona, Spain.
J Phys Chem A. 2023 Nov 30;127(47):9944-9958. doi: 10.1021/acs.jpca.3c04975. Epub 2023 Nov 14.
Perylenediimide molecules constitute a family of chromophores that undergo singlet fission, a process in which an excited singlet state converts into lower energy triplets on two neighboring molecules, potentially increasing the efficiency of organic solar cells. Here, the nonorthogonal configuration interaction method is applied to study the effect of the different crystal packing of various perylenediimide derivatives on the relative energies of the singlet and triplet states, the intermolecular electronic couplings, and the relative rates for singlet fission. The analysis of the wave functions and electronic couplings reveals that charge transfer states play an important role in the singlet fission mechanism. Dimer conformations where the PDI molecules are at large displacements along the long axis and short on the short axis are posed as the most favorable for singlet fission. The role of the substituent at the imide group has been inspected concluding that, although it has no effect in the energies, for some conformations it significantly influences the electronic couplings, and therefore, replacing this substituent with hydrogen may introduce artifacts in the computational modeling of the PDI molecules.
苝二酰亚胺分子构成了一类发色团，这类发色团会发生单重态裂变，在这个过程中，一个激发单重态会在两个相邻分子上转化为能量更低的三重态，这有可能提高有机太阳能电池的效率。在此，采用非正交构型相互作用方法来研究各种苝二酰亚胺衍生物的不同晶体堆积对单重态和三重态的相对能量、分子间电子耦合以及单重态裂变的相对速率的影响。对波函数和电子耦合的分析表明，电荷转移态在单重态裂变机制中起着重要作用。苝二酰亚胺分子沿长轴有大位移且沿短轴较短的二聚体构象被认为是最有利于单重态裂变的。对酰亚胺基团上取代基的作用进行了研究，得出的结论是，尽管它对能量没有影响，但对于某些构象，它会显著影响电子耦合，因此，用氢取代这个取代基可能会在苝二酰亚胺分子的计算建模中引入假象。
