B2 (Marian)

Abstract:

Thermally activated delayed fluorescence (TADF) and thermally activated fluorescence (TAF) are recently proposed concepts for improving the internal quantum efficiency (IQE) of OLEDs. Intersystem crossing (ISC) and reverse intersystem crossing (rISC) are key processes for the interconversion of singlet and triplet excited states, thus enabling up to 100% IQE of electroluminescent devices.

The main objective of this project is to identify the factors that control the luminescence properties of linear copper complexes with N-heterocyclic carbene ligands (B1, Ganter) and of the metal-free bi(hetero)aryl donor–acceptor systems (A1, Müller).
Together with our experimental partners, substitution patterns will be designed to improve the luminescence properties of the core compounds. The multi-reference methods and other computational tools developed in our group enable us to investigate the electronic structures of the emitters as well as the energetics and mechanisms of the spin-allowed and spin-forbidden transitions. Computed fluorescence and phosphorescence lifetimes as well as rate constants for ISC and rISC processes will be compared with the time constants derived from time-resolved experiments (B3, Gilch). Resonant singlet-singlet excitation energy transfer (EET) between a TADF donor and a strongly fluorescent acceptor is at the heart of TAF. To estimate the loss of triplet population through Dexter EET, a method for computing intermolecular triplet–triplet electronic coupling matrix elements from monomer transition densities will be devised. EET rate constants can be compared directly to experiment (A2, Seidel) will be determined for suitable pairs of TADF donors and strongly fluorescent acceptors.