Bardeen Christopher J
Department of Chemistry, University of California, Riverside, California 92521; email:
Annu Rev Phys Chem. 2014;65:127-48. doi: 10.1146/annurev-physchem-040513-103654. Epub 2013 Dec 2.
The photophysical behavior of organic semiconductors is governed by their excitonic states. In this review, I classify the three different exciton types (Frenkel singlet, Frenkel triplet, and charge transfer) typically encountered in organic semiconductors. Experimental challenges that arise in the study of solid-state organic systems are discussed. The steady-state spectroscopy of intermolecular delocalized Frenkel excitons is described, using crystalline tetracene as an example. I consider the problem of a localized exciton diffusing in a disordered matrix in detail, and experimental results on conjugated polymers and model systems suggest that energetic disorder leads to subdiffusive motion. Multiexciton processes such as singlet fission and triplet fusion are described, emphasizing the role of spin state coherence and magnetic fields in studying singlet ↔ triplet pair interconversion. Singlet fission provides an example of how all three types of excitons (triplet, singlet, and charge transfer) may interact to produce useful phenomena for applications such as solar energy conversion.
有机半导体的光物理行为由其激子态决定。在这篇综述中，我对有机半导体中通常遇到的三种不同激子类型（弗伦克尔单重态、弗伦克尔三重态和电荷转移态）进行了分类。讨论了在固态有机系统研究中出现的实验挑战。以结晶并四苯为例，描述了分子间离域弗伦克尔激子的稳态光谱。我详细考虑了局域激子在无序基质中扩散的问题，共轭聚合物和模型系统的实验结果表明，能量无序导致亚扩散运动。描述了多激子过程，如单重态裂变和三重态融合，强调了自旋态相干和磁场在研究单重态⇄三重态对相互转换中的作用。单重态裂变提供了一个例子，说明三种激子类型（三重态、单重态和电荷转移态）如何相互作用，以产生对太阳能转换等应用有用的现象。
