Structurally controlled singlet-triplet splitting for blue star-shaped thermally activated delayed fluorescence emitters incorporating the tricarbazoles-triazine motifs

摘要

Here, we report the design strategy and synthesis of a new series of star-shaped, structurally controlled singlet-triplet splitting for blue thermally activated delayed fluorescence (TADF) emitters, CZ-TRZ, MeCZ-TRZ, and 2MeCZ-TR2, composed with three carbazoles as donor and triazine as an acceptor. This system is incorporating from three donor units, carbazole derivatives at para-position with directly fused to the strong acceptor, triazine backbone linked by a twisted ortfio-methylphenyl bridge to increase the steric effect as well as to control the torsion angle. Moreover, the electronic interaction between the donor and acceptor unit plays a crucial role in the TADF mechanism as well as tuning the emission peak. The photophysical and optoelectronic properties of the materials were explored. The OLED devices were fabricated and exhibit efficient device performance with a maximum external quantum efficiency (EQE) of 10.9%, 14.4% and 15.9% at 473, 484, 484 nm for CZ-TRZ, MeCZ-TRZ, and 2MeCZ-TRZ, respectively.