Northey T, Keane T, Eng J, Penfold T J
Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom.
Faraday Discuss. 2019 Jul 11;216(0):395-413. doi: 10.1039/c8fd00174j.
Excited state energy transfer in disordered systems has attracted significant attention owing to the importance of this phenomenon in both artificial and natural systems that operate in electronically excited states. Of particular interest, especially in the context of organic electronics, is the dynamics of triplet excited states. Due to their weak coupling to the singlet manifold they can often act as low energy trapping sites and are therefore detrimental to device performance. Alternatively, by virtue of their long lifetime they can lead to enhanced diffusion lengths important for organic photovoltaics (OPV). Herein, we explore the triplet energy transfer mechanism from dichlorobenzene to thioxanthone in methanol solution. We rationalise previous experimental observations as arising from preferential population transfer into the lowest triplet state rather than the higher lying triplet state that is closer in energy. The reason for this is a delicate balance between the electronic coupling, reorganisation energy and the energy gap involved. The present results provide the understanding to potentially develop a hot exciton mechanism in materials for organic light emitting diodes (OLED) to achieve higher device efficiencies.
无序系统中的激发态能量转移因其在以电子激发态运行的人工和自然系统中的重要性而备受关注。特别令人感兴趣的是三重态激发态的动力学，尤其是在有机电子学的背景下。由于它们与单重态流形的弱耦合，它们常常可以作为低能俘获位点，因此对器件性能不利。或者，由于它们的长寿命，它们可以导致对有机光伏（OPV）很重要的扩散长度增加。在此，我们探索了甲醇溶液中从二氯苯到噻吨酮的三重态能量转移机制。我们将先前的实验观察结果解释为优先的布居转移到最低三重态而非能量更接近的较高三重态。其原因在于电子耦合、重组能和所涉及的能隙之间的微妙平衡。目前的结果为在有机发光二极管（OLED）材料中潜在地开发热激子机制以实现更高的器件效率提供了理解。
