Measuring Nanoscale Exciton Motion & Annihilation in Single Molecules with Photon Statistics

有机半导体是一种重要的光电技术，在有机发光二极管(OLED)显示器中得到了广泛的应用。在电或光激发下，激发态准粒子被称为激子。激子可以在材料衰变和发光之前在材料中移动。如果两个激子相遇，其中一个通常可以消除另一个(这个过程被称为湮灭)，这是一种减少光发射的损失机制。对于高亮度的OLED应用，如照明，需要高的激子密度，因此激子的运动和湮灭可以抑制光发射。激子运动和湮没的测量通常是具有挑战性的，因此在理解这些过程方面存在着知识鸿沟，这限制了新材料的合理设计。在这个方案中，将对单分子上激子之间的绝对数目、运动和湮灭进行独特的新的无背景单分子光谱测量。通过测量具有已知几何结构和不同化学部分的分子，将建立分子结构和激子如何运动和湮灭之间的关系。有机半导体材料的实现能够维持高激子密度，适用于照明或有机激光，取决于对基本知识的理解。因此，这项工作的愿景是弥合理解方面的知识差距，为先进的下一代有机半导体材料的设计照亮一条道路，该材料将具有增强的器件性能。

Organic semiconductors are an important optoelectronic technology that have achieved widespread adoption in displays with organic light emitting diodes (OLEDs). Upon electrical or photo excitation, excited state quasiparticles called excitons are created. Excitons can move in the material before decaying and emitting light. If two excitons meet, one can often eliminate the other (a process called annihilation), a loss mechanism that reduces light emission. For high brightness application of OLEDs such as lighting, high exciton densities are required, thus the movement of excitons and their annihilation can curb light emission. Exciton motion and annihilation are typically challenging to measure, therefore there is a knowledge gap in understanding these processes that limits the rational design of new materials.In this proposal unique new background-free single molecule spectroscopic measurements of the absolute number of, motion and annihilation between excitons on single molecules will be made. By measuring molecules with known geometries and different chemical moieties, the relationship between the structure of a molecule and how excitons move and annihilate will be established. The realisation of organic semiconductor materials that can sustain high exciton densities, suitable for use in lighting or organic lasers depends upon fundamental understanding. Thus, the vision in this work is to close the knowledge gap in understanding, lighting a path towards the design of advanced next generation organic semiconductor materials that will have enhanced device performance.