Zhang Tao, Rai Deepesh, Holmes Russell J
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States.
J Phys Chem Lett. 2021 Jan 28;12(3):966-972. doi: 10.1021/acs.jpclett.0c02825. Epub 2021 Jan 19.
Probing triplet transport in singlet fission materials can be challenging due to the presence of multiple diffusing species. We present a device-based method to measure the intrinsic triplet diffusion length () in organic semiconductor thin films exhibiting singlet fission. Triplet states are optically injected into the singlet fission material of interest via energy transfer from an adjacent thin film characterized by strong spin-orbit coupling. Injected triplets migrate through the full thickness of the material before undergoing dissociation at a donor-acceptor interface. By modeling the ratio of injector and acceptor photocurrent as a function of layer thickness, the triplet is extracted separate from processes of unknown efficiency including singlet fission and diffusion. In considering three archetypical fission systems, a wide range is found for the triplet , ranging from 3.3 ± 0.4 nm for 5,12-bis((triisopropylsilyl)ethynyl)tetracene to 17.1 ± 1.3 nm for pentacene and 32.1 ± 2.6 nm for tetracene.
由于存在多种扩散物种，探究单线态裂变材料中的三线态传输可能具有挑战性。我们提出了一种基于器件的方法来测量表现出单线态裂变的有机半导体薄膜中的固有三线态扩散长度（）。通过从具有强自旋 - 轨道耦合的相邻薄膜进行能量转移，三线态被光注入到感兴趣的单线态裂变材料中。注入的三线态在供体 - 受体界面发生解离之前，会在材料的整个厚度范围内迁移。通过将注入器和受体光电流的比率建模为层厚度的函数，可以从包括单线态裂变和扩散在内的未知效率过程中分离出三线态扩散长度。在考虑三种典型的裂变系统时，发现三线态扩散长度的范围很广，从5,12 - 双（（三异丙基甲硅烷基）乙炔基）并四苯的3.3±0.4纳米到并五苯的17.1±1.3纳米以及并四苯的32.1±2.6纳米。
