Synthesis and Photophysical Properties of Ortho-Donor-Appended TADF Compounds with Different Triarylboron Acceptors

Abstract

As the development of red, green, and blue emitters are growing in display technology, thermally activated delayed fluorescence (TADF) materials have become great attention as efficient emitters in organic light emitting diodes (OLEDs) due to its ability to obtain high efficiency. However there are still problems such as lack of color purity, stability, and practical use in device. Since it was demonstrated that the acceptor moiety plays a crucial role in attaining strong TADF properties, we have been interested to investigate the effect of different acceptors in triarylboron moieties. Into the ortho position of phenyl ring substituted with diphenylacridine as fixed electron donor, different triarylboron acceptors, such as cyclic boraanthracene (DPACoDB), oxaborin (DPACoOB), as well as dimesitylboron (DPACoB) were introduced to give ortho-donor-appended compounds. DPACoDB and DPACoOB which contain cyclic triarylboron showing blue-shifted emission both in toluene solution and PMMA film, compared to non-cyclic DPACoB. This finding was supported by 11B NMR data which shifted the cyclic compounds to the higher magnetic field and by cyclic voltammetry data related to the increasing of HOMOLUMO gap. All compounds demonstrated high quantum efficiency (PL = 0.910.99) and displayed high thermal stability, making these compounds a good candidate as highly efficient TADF-OLED emitters.