Thermally activated delayed fluorescence (TADF) - from rational design to OLED applications. (R-9583)

- In recent years, a number of organic semiconducting materials have been developed to exploit the new light emission principle of thermally activated delayed fluorescence (TADF). This concept enables to realize unique optical and electronic properties arising from the efficient thermal equilibration of the lowest singlet (S1) and triplet (T1) excited states of organic fluorophores. As a result, TADF-based organic light-emitting diodes (OLEDs) show significantly upgraded device performances, comparable to those provided by the state of the art rare metal complexes. To realize efficient TADF, organic luminophores require a very small energy difference (deltaEST) between their S1 and T1 excited states, which enhances the T1->S1 reverse intersystem crossing rate. Such excited state equilibration is attainable by intramolecular charge transfer within systems containing spatially separated donor and acceptor moieties. The critical point of this molecular design is the combination of a small deltaEST (<= 200 meV) with a reasonable radiative decay rate (> 10 E6 s-1) to overcome competitive non-radiative pathways, leading to highly luminescent materials. In the presented project, advanced TADF materials will be rationally designed (based on computational pre-screening), synthesized and (photophysically) characterized and then implemented in OLED devices. As such, we aim at a substantial contribution to the transition from a purely academic field to an economic and societal valuable technology.

Keywords:Fluorescence spectroscopy, ORGANIC SYNTHESIS, Thermally activated delayed fluorescence (TADF)

Disciplines:Chemical characterisation of materials, Organic chemical synthesis, Molecular and organic electronics