美国康奈尔大学Musser, Andrew J.团队报道了纠缠三重态的相干光激发。相关研究成果于2024年6月19日发表在《自然—化学》。

有机半导体的功能性质由光学亮态和暗态之间的相互作用来定义。有机器件需要在这些亮歧管和暗歧管之间进行快速转换以获得最大效率，而实现这一点的一种方法是通过多激子产生（S₁→¹TT）。暗态¹TT典型地由光激发之后的亮S₁产生；然而，有关机制细节的争论十分激烈。

该文中，研究人员报道了一种¹TT产生途径，在该途径中，它可以被相干光激发，而不涉及任何明亮的S₁。使用<10 fs的瞬态吸收光谱和亚共振泵浦，¹TT直接从基态产生。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，研究人员确定了实现这一禁用途径的关键材料特性。通过一种极其简单的技术，这一结果为深入了解有机材料中的¹TT和其他暗态打开了新的机制之门。

附：英文原文

Title: Coherent photoexcitation of entangled triplet pair states

Author: Kim, Juno, Bain, David C., Ding, Vivian, Majumder, Kanad, Windemuller, Dean, Feng, Jiaqi, Wu, Jishan, Patil, Satish, Anthony, John, Kim, Woojae, Musser, Andrew J.

Issue&Volume: 2024-06-19

Abstract: 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.

DOI: 10.1038/s41557-024-01556-3

Source: https://www.nature.com/articles/s41557-024-01556-3