Decisive role of heavy-atom orientation for efficient enhancement of spin-orbit coupling in organic thermally activated delayed fluorescence emitters

In view of the rapidly growing interest in the hybrid materials for heavy-metal-free optoelectronics, the research described here aimed to confirm the potential ability of abundant heavy atoms (HAs) in improving key parameters of organic emitters with thermally activated delayed fluorescence. Namely, the enhancement of reverse intersystem crossing (rISC) while keeping a reasonable value of fluorescence rate was investigated in red emitters with bromine atom(s) introduced into the ortho positions of the N,N-ditolylaniline donor fragment.