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

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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.