单重态激子裂分指的是在有机分子中一个单重态激子与相邻的基态发色团相互作用形成两个三重态激子的过程。利用这种多激子效应制成的光伏器件有望突破肖克利-奎瑟限制,使光电转换的理论效率由30%提高到44.4%。近年来各国科学家在裂分材料的设计合成和器件化应用方面取得了一定的进展,但是对于激子裂分物理本质的认知仍然存在争议和分歧。本文较为系统地介绍了激子裂分材料的最新进展和本研究组的相关工作。简要回顾了激子裂分的发展历史,从概念、裂分的发生条件和作用机制三方面介绍了激子裂分过程,综述了具有分子间和分子内裂分性质的材料的最新研究成果。在系统归纳激子裂分研究现状的基础上对单重态激子裂分的发展趋势和应用探索指出了可能的方向。
Singlet exciton fission is the process by which a high-energy singlet exciton splits into two low-energy triplet excitons. Organic solar cells based on singlet fission have the potential to exceed the Shockley-Queisser limit and, in doing so, may improve their efficiency from 30% to 44.4%. Although progress in singlet fission materials and photovoltaic devices has accelerated with recent research, many challenges and debates remain with regard to clarifying the relationship between molecule structures and the rate and efficiency of singlet fission. This review addresses recent advances in singlet fission materials and summarizes the work of our own research group. We begin by introducing the background of singlet fission, following with the general concept, the requirements for singlet fission to proceed, and the applications of transient absorption spectroscopy. Two mechanisms have been proposed to explain singlet fission molecules, intermolecular and intramolecular singlet fission, and these two types of materials are summarized, focusing on dimers, which are novel structures that undergo efficient intramolecular singlet fission. Based on the latest developments in singlet fission, we discuss the possible future advances in, and prospects for the application of, singlet fission materials.