Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, UK.
Nat Chem. 2013 Dec;5(12):1019-24. doi: 10.1038/nchem.1801. Epub 2013 Nov 17.
Singlet exciton fission, the spin-conserving process that produces two triplet excited states from one photoexcited singlet state, is a means to circumvent the Shockley-Queisser limit in single-junction solar cells. Although the process through which singlet fission occurs is not well characterized, some local order is thought to be necessary for intermolecular coupling. Here, we report a triplet yield of 200% and triplet formation rates approaching the diffusion limit in solutions of bis(triisopropylsilylethynyl (TIPS)) pentacene. We observe a transient bound excimer intermediate, formed by the collision of one photoexcited and one ground-state TIPS-pentacene molecule. The intermediate breaks up when the two triplets separate to each TIPS-pentacene molecule. This efficient system is a model for future singlet-fission materials and for disordered device components that produce cascades of excited states from sunlight.
单线态激子裂变是一种自旋守恒过程，它能将一个光激发单线态转化为两个三重态激发态，是规避单结太阳能电池中肖克利-奎塞尔限制的一种手段。尽管单线态裂变发生的过程尚未得到很好的描述，但人们认为分子间耦合需要一定的局部有序性。在这里，我们报告了在双（三异丙基硅基乙炔基（TIPS））五苯溶液中，三重态产率达到 200%，三重态形成速率接近扩散极限。我们观察到一个瞬态束缚激基复合物中间体，由一个光激发的和一个基态 TIPS-五苯分子的碰撞形成。当两个三重态分离到每个 TIPS-五苯分子时，中间体就会分解。这个高效的体系是未来单线态裂变材料和产生来自阳光的激发态级联的无序器件组件的模型。
