Substituent engineering of the diboron molecular architecture for a nondoped and ultrathin emitting layer

Abstract

Owing to the high technology maturity of thermally activated delayed fluorescence (TADF) emitter design with a specific molecular shape, extremely high-performance organic light‐emitting diodes (OLEDs) have recently been achieved via...

A Diboron-Based Thermally Activated Delayed Fluorescent Material for Versatile Applications of Organic Light-Emitting Diodes

“…And the energy gap between S 1 and T 1 (ΔE ST ) is 19.4 meV, which is in good agreement with the calculated results with BMK/6-31G(d) (Tables S1 and S2). Such value is relatively low among reported diboron-based derivatives 27 , 30 and beneficial for accelerating RISC. 4,7 The ΔE ST of the neat film is slightly larger than that of the doped film due to the formation of dimer or trimer of PhCzDBA, which is supported by its NTO results.…”

“…The direction of TEDM is more elongated along the long molecular axis, due to the expanded plane of terminal diphenylcarbazole moiety. Moreover, the TEDM vector of PhCzDBA has a lower z component, which reveals the feature of highly horizontal emitting dipole orientation …”

“…The donor–acceptor–donor (D-A-D) or A-D-A configuration was known to generate an efficient TADF, high RISC rate constants, and high horizontal dipole ratios. − Besides, several results indicate that boron-containing materials had exhibited outstanding efficiency , and lifetime. , Our previous studies based on the framework of 9,10-dihydro-9,10-diboraanthracene (DBA) have realized efficient TADF with high efficiency and reduced roll-off due to the suppressed singlet–triplet annihilation (STA) and triplet–triplet annihilation (TTA) . The diboron-based materials, CzDBA and t BuCzDBA, exhibited high photoluminescence quantum yields (PLQYs) of over 82% in their neat films, making high-performance nondoped OLEDs . Furthermore, the following work by Kotadiya et al demonstrated CzDBA’s extended operational lifetime and good quantum efficiency in nondoped devices, which suggested that DBA-based compounds are promising for lifetime devices.…”

“…32 The diboron-based materials, CzDBA and tBuCzDBA, exhibited high photoluminescence quantum yields (PLQYs) of over 82% in their neat films, making high-performance nondoped OLEDs. 27 Furthermore, the following work by Kotadiya et al 36 In this work, a newly designed compound, PhCzDBA, is presented and synthesized. The phenyl rings were introduced on the 3 and 6 positions of the carbazole moiety to prevent the carbazole from oxidation, 37 increase the molecule's rigidity, and reduce intermolecular stacking.…”

“…Moreover, the TEDM vector of PhCzDBA has a lower z component, which reveals the feature of highly horizontal emitting dipole orientation. 27 We further analyzed the PhCzDBA structures between the ground state (S 0 ) and the lowest singlet excited state (S 1 ) by root-mean-square deviation (RMSD) method to discuss the molecular rigidity, as shown in Figure S2. PhCzDBA exhibited minor conformation changes between S 0 and S 1 states and a small RMSD value of 0.03 Å, which indicates the effective suppression of the molecular configuration relaxation during the radiative transition process.…”