Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
J Phys Chem B. 2010 Nov 18;114(45):14168-77. doi: 10.1021/jp907392q. Epub 2010 Feb 25.
In traditional solar cells one photon absorbed can lead to at most one electron of current. Singlet fission, a process in which one singlet exciton is converted to two triplet excitons, provides a potential improvement by producing two electrons from each photon of sufficient energy. The literature contains several reports of singlet fission in various systems, but the mechanism of this process is poorly understood. In this paper we examine a two-step mechanism with a charge transfer state intermediate, applicable when the initial excited state is localized. Density matrix theory is used to examine how various molecular properties such as orbital energies and electronic couplings affect singlet fission yield in the regime of fast, coherent electron transfer. Several promising chromophores are discussed and density functional theory is used to predict fission yield for each in the context of this mechanism. Finally, implications for chromophore design are discussed, and future experiments are suggested.
在传统的太阳能电池中，一个光子吸收最多可以导致一个电子电流。单线态裂变是一种将一个单线态激子转化为两个三线态激子的过程，通过将每个具有足够能量的光子产生两个电子，提供了一种潜在的改进方法。文献中报道了各种系统中的单线态裂变，但该过程的机制仍不清楚。在本文中，我们研究了一种具有电荷转移态中间体的两步机制，适用于初始激发态为局域化的情况。密度矩阵理论用于研究各种分子性质（如轨道能量和电子耦合）如何影响快速、相干电子转移条件下的单线态裂变产率。讨论了几个有前途的发色团，并使用密度泛函理论在这种机制的背景下预测了每个发色团的裂变产率。最后，讨论了发色团设计的意义，并提出了未来的实验建议。
