Development and application of relativistic propagator methods for accurate theoretical descriptions of organic triplet emitters

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Organic electronics is one of the future key technologies due to its broad applicability and low energy consumption. In contrast to semiconductor devices, that are to be described by methods of solid state physics, organic electronics is based on molecular structures necessitating different quantum chemical approaches. In both cases numerical requirements are very high asking for the development of efficient theoretical methods in order to gain deep insight and to keep up with technological progress. In this project we focus on organic triplet emitters containing heavy transition metals that are exhibiting very high quantum yields. This high efficiency can be achieved by providing mechanisms that lead to a nearly complete recombination of each injected electron/hole pair into the material. This exciton is localized at the emitting center and shows a statistical mixture of 25% singlet and 75% triplet character. The triplet excitons are not directly amenable to recombination which changes drastically if heavy transition metals are introduced to the complex. Hereby also the triplet states recombine very efficiently by presence of strong spin-orbit coupling (SOC). Therefore, an accurate description of all effects caused by the introduction of heavy atoms, the inclusion of electron correlation and of the environment is therefore mandatory for the design of new efficient triplet emitters. An ideally suited method to achieve this was developed in our group and is based on the fully relativistic polarization propagator. Methods applied so far often introduce approximative treatments of SOC or are quite complex in their handling. This should be avoided in our new production suite. The already available numerical algorithms and implementations will be extended in order to tackle large organic metal complexes in a solvent or specific molecular environment. By this it is intended to support material science in the development of efficient OLEDs. Additionally, far-reaching opportunities for scientific cooperations with experimentally working groups are planned to make the project most fruitful.