Understanding Thermally Activated Delayed Fluorescence in Cu(I) Complexes and Metal-Free Donor-Acceptor Systems: A Quantum Chemical Approach

热激活延迟荧光（TADF）被认为是一种重要的新兴技术，用于生成高性能的电致发光器件，用于显示和照明系统。该研究的主要目标是更好地了解决定TADF概率的因素，因为这是设计和优化第三代OLED发射器的关键一步。尽管近年来对这一课题进行了大量的研究，但仍然缺乏对TADF的完整和一致的合理化。一个小的单重态-三重态的电子激发态分裂不足以使TADF发生。相反，必须了解控制激发态过程的相对概率的分子参数，如分子内电荷和能量转移、系统间交叉、反向系统间交叉、荧光、磷光和非辐射失活。量子化学可以极大地促进这种理解。特别是，它可以提供光谱暗态及其与发光态耦合的详细信息，这些信息很难甚至不可能单独从实验数据中获得。此外，从引线结构出发，量子化学可以很容易地评估化学取代对发射器光物理的影响。在验证了我们的理论方法之后，我们将制定策略来提高d10过渡金属配合物和纯有机TADF发射器的电致发光效率，无论是通过改变化学结构还是通过增加状态的电子或振动密度。在前三年，我们将重点研究TADF发射极的本征特性。这包括环境影响，但不包括TADF发射器与宿主分子的激子耦合。后一个主题将在项目的后期讨论。

Thermally activated delayed fluorescence (TADF) is looked upon as a significant emerging technology for generating highly performant electroluminescent devices for displays and lighting systems. The main objective of the proposed research is to gain a better insight into the factors that determine the probability of TADF as this is a key step towards the design and optimization of third-generation OLED emitters. Despite intensive research on this topic in the latest years, a complete and consistent rationalization of TADF is still missing. A small singlet-triplet splitting of the electronically excited emitter states alone is not sufficient for TADF to take place. Rather, the molecular parameters that steer the relative probabilities of excited-state processes such as intramolecular charge and energy transfer, intersystem crossing, reverse intersystem crossing, fluorescence, phosphorescence and nonradiative deactivation have to be understood. Quantum chemistry can substantially contribute to this understanding. In particular, it can provide detailed information about spectroscopically dark states and their coupling to the luminescent state, information that is difficult or even impossible to obtain from experimental data alone. Moreover, starting from a lead structure, quantum chemistry can easily assess the effects of chemical substitution on the photophysics of the emitter. After having validated our theoretical methods, we will develop strategies to enhance the electroluminescence efficiency of d10 transition metal complexes and purely organic TADF emitters, be it by varying the chemical structure or by increasing the electronic or vibrational density of states. In the first three years, we will focus on intrinsic TADF emitter properties. This includes environment effects but not the excitonic coupling of the TADF emitter to host molecules. The latter topic shall be addressed at a later stage of the project.