Department of Chemistry and Molecular Biology , University of Gothenburg , Kemigården 4 , Gothenburg , Sweden.
Department of Chemical and Biological Engineering/Organic Chemistry , Chalmers University of Technology , SE-412 96 Gothenburg , Sweden.
J Am Chem Soc. 2019 Jun 19;141(24):9578-9584. doi: 10.1021/jacs.9b02302. Epub 2019 Jun 5.
The triplet pair is the key functional unit in triplet-triplet annihilation photon upconversion. The same molecular properties that stabilize the triplet pair also allow dimers to form on the singlet energy surface, creating an unwanted energy relaxation pathway. Here we show that excimer formation most likely is a consequence of a triplet dimer formed before the annihilation event. Polarity-dependent studies were performed to elucidate how to promote wanted emission pathways over excimer formation. Furthermore, we show that the yield of triplet-triplet annihilation is increased in higher-viscosity solvents. The results will bring new insights in how to increase the upconversion efficiency and how to avoid energy-loss channels.
三重态对是三重态-三重态湮灭上转换的关键功能单元。使三重态对稳定的相同分子性质也允许在单重态能量表面上形成二聚体，从而产生不需要的能量弛豫途径。在这里，我们表明，激基复合物的形成很可能是在湮灭事件之前形成的三重态二聚体的结果。进行了极性依赖性研究，以阐明如何促进想要的发射途径而不是形成激基复合物。此外，我们表明，三重态-三重态湮灭的产率在较高粘度的溶剂中增加。该结果将为如何提高上转换效率以及如何避免能量损失途径提供新的见解。
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