AUTHOR=Krotkus Simonas , Matulaitis Tomas , Diesing Stefan , Copley Graeme , Archer Emily , Keum Changmin , Cordes David B. , Slawin Alexandra M. Z. , Gather Malte C. , Zysman-Colman Eli , Samuel Ifor D. W. 

TITLE=Fast Delayed Emission in New Pyridazine-Based Compounds

JOURNAL=Frontiers in Chemistry

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.572862

DOI=10.3389/fchem.2020.572862

ISSN=2296-2646

ABSTRACT=<p>Three novel donor-acceptor molecules comprising the underexplored pyridazine (Pydz) acceptor moiety have been synthesized and their structural, electrochemical and photophysical properties thoroughly characterized. Combining Pydz with two phenoxazine donor units linked via a phenyl bridge in a <italic>meta</italic> configuration (<bold>dPXZMePydz</bold>) leads to high reverse intersystem crossing rate <italic>k</italic><sub>RISC</sub> = 3.9 · 10<sup>6</sup> s<sup>−1</sup> and fast thermally activated delayed fluorescence (TADF) with &lt;500 ns delayed emission lifetime. Efficient triplet harvesting via the TADF mechanism is demonstrated in OLEDs using <bold>dPXZMePydz</bold> as the emitter but does not occur for compounds bearing weaker donor units.</p>