The functional properties of organic semiconductors are defined by the interplay between optically bright and dark states. Organic devices require rapid conversion between these bright and dark manifolds for maximum efficiency, and one way to achieve this is through multiexciton generation (S₁→¹TT). The dark state ¹TT is typically generated from bright S₁ after optical excitation; however, the mechanistic details are hotly debated. Here we report a ¹TT generation pathway in which it can be coherently photoexcited, without any involvement of bright S₁. Using <10-fs transient absorption spectroscopy and pumping sub-resonantly, ¹TT is directly generated from the ground state. Applying this method to a range of pentacene dimers and thin films of various aggregation types, we determine the critical material properties that enable this forbidden pathway. Through a strikingly simple technique, this result opens the door for new mechanistic insights into ¹TT and other dark states in organic materials.

有机半导体的功能特性是由光学亮态和暗态之间的相互作用定义的。有机器件需要在这些亮和暗流形之间快速转换以获得最大效率，实现这一目标的一种方法是通过多激子生成（S ₁ → ¹ TT）。暗态 ¹ TT通常由光激发后的亮S ₁ 产生；然而，其机制细节引起了激烈争论。在这里，我们报告了一种 ¹ TT 生成途径，其中它可以被相干地光激发，而无需任何明亮的 S ₁ 的参与。使用<10-fs瞬态吸收光谱和亚共振泵浦， ¹ TT直接从基态生成。将该方法应用于一系列并五苯二聚体和各种聚集类型的薄膜，我们确定了实现这一禁止途径的关键材料特性。通过一种极其简单的技术，这一结果为了解 ¹ TT 和有机材料中其他暗态的新机制打开了大门。