Diboron-Based Delayed Fluorescent Emitters with Orange-to-Red Emission and Superior Organic Light-Emitting Diode Efficiency

For
the application of organic light-emitting diodes (OLEDs) in lighting
and panels, the basic requirement is to include a full spectrum color
range. Compared with the development of blue and green luminophores
in thermally activated delayed fluorescence (TADF) technology, the
progress of orange-to-red materials is slow and needs further investigation.
In this study, three diboron compound-based materials, dPhADBA, dmAcDBA,
and SpAcDBA, were designed and synthesized by nucleophilic arylation
of three amine donors on 9,10-diboraanthracene (DBA) in a two-step
reaction. With increasing electron-donating ability, they show orange-to-red
emission with TADF characteristics. The electroluminescence of these
diboron compounds exhibits emissions λmax at 613,
583, and 567 nm for dPhADBA, dmAcDBA, and SpAcDBA, respectively. It
is noteworthy that the rod-like D-A-D structures can achieve high
horizontal ratios (84–86%) and outstanding device performance
for orange-to-red TADF OLEDs: the highest external quantum efficiencies
for dPhADBA, dmAcDBA, and SpAcDBA are 11.1 ± 0.5, 24.9 ±
0.5, and 30.0 ± 0.8%, respectively. Therefore, these diboron-based
molecules offer a promising avenue for the design of orange-to-red
TADF emitters and the development of highly efficient orange-to-red
OLEDs.