Design of highly stable thermally activated delayed fluorescence emitters via the overlap degree of HOMO-LUMO distributions

Two questions including the judgement of thermally activated delayed fluorescence (TADF) property and high stability are crucial for designing TADF emitters. In this work, based on the experimental TADF emitters, we investigated the essential reason of improving the stability of TADF device by introducing tert-butyl and phenyl into the peripheral position of carbazole, and suggested to judge the TADF property via the concrete HOMO-LUMO overlap calculation. To design highly stable TADF emitters, several pairs of positional isomers combining tert-Butyl-substituted carbazole as donor with different acceptors are designed by connecting the donor and acceptor groups through the orth-, meta- and para-position. Via the HOMO-LUMO overlap calculation, the potential TADF emitters have been point out. Our results find that the HOMO-LUMO overlap values are dependent on the linkage styles and acceptor species. For example, the designed molecules m-Cz-BF/BF-Cz/NOBF2-DTCz/CPS, o-CNImPy-Cz/PQM-Cz, and m-, p-Cz-NAI have the potential to perform better TADF performance than other isomers. These results indicate that the HOMO-LUMO overlap could be used to identify synthetic motifs for promising TADF candidates among structural isomers. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

In this study, the stability of TADF devices was improved by introducing tert-butyl and phenyl into the peripheral position of carbazole. The TADF property was judged through specific HOMO-LUMO overlap calculation. By designing positional isomers combining tert-Butyl-substituted carbazole with different acceptors, potential TADF emitters were identified based on HOMO-LUMO overlap calculation. The results suggest that HOMO-LUMO overlap can be used to identify promising synthetic motifs for TADF candidates among structural isomers.