Molecular Design and Synthesis of Dicarbazolophane-Based Centrosymmetric Through-Space Donors for Solution-Processed Thermally Activated Delayed Fluorescence OLEDs

Abstract

Conjugation-extended carbazolophane donors, dicarbazolophanes (DCzp), were designed and synthesized using a multifold stepwise Pd-catalyzed Buchwald–Hartwig amination/ring cyclization process. Furthermore, elaboration of the DCzp core is possible with the introduction of pendant carbazole derivative groups. This provides a way to tune the optoelectronic properties of the thermally activated delayed fluorescence (TADF) compounds DCzpTRZtBu, dtBuCzDCzpTRZtBu, and dMeOCzDCzpTRZtBu. Solution-processed organic light-emitting diodes (OLEDs) were fabricated and achieved a maximum external quantum efficiency (EQEmax) of 8.2% and an EQE of 7.9% at 100 cd/m2.

Synthetic progress of organic thermally activated delayed fluorescence emitters via C–H activation and functionalization

“…The Zysman-Colman group employed the Pd 2 (dba) 3 -XPhos-PivOH system to activate the intramolecular dehydrochlorination CÀH transformations, synthesizing electron-withdrawing group modified and centrosymmetric carbazolophane donors for constructing TADF emitters (CNCzpPhTRZ, CF 3 CzpPhTRZ, DCzpTRZtBu, dtBuCzDCzpTRZtBu, and dMeOCzDCzpTRZtBu). 121,122 The good tolerance of the Pd-catalyzed intramolecular dehydrohalogenated CÀH bond activation to functional groups promoted the highly efficient synthesis of 2-methoxy-3methyl-9H-carbazole (Scheme 20a), which was further utilized in constructing circularly polarized thermally activated delayed fluorescence (CP-TADF) emitters (B 2 TPNF 2 and B 2 CNPyF 2 ) with D-A units separated by oxygen atoms. 123 (Scheme 20b), employing a design strategy involving chiral perturbation.…”

A periphery hindered strategy with a dopant and sensitizer for solution-processed red TSF-OLEDs with high color purity

“…Therefore, the PL decay curves had longer lifetimes than that of 4CzTPN. The computing method of the rate constant of the FET process could be simplified to eqn (1), where the R DA is the intermolecular distance of TADF sensitizer and dopant, and t D is the TADF sensitizer lifetime. Additionally, the R DA value was negatively correlated with the dopant concentration, which decreased obviously with enhanced molecular concentrations.…”

“…Metal-free organic materials that exhibit thermally activated delayed fluorescence (TADF) characteristic with the small singlet-triplet energy gap (DE ST ) and 100% internal quantum efficiency (IQE) are an attractive type of functional materials that have led to a breakthrough in the development of organic light-emitting diodes (OLEDs). [1][2][3][4][5][6][7][8] Although TADF materials help achieve high efficiency in manufacturing red, green, and blue devices, the nature of inherent charge transfer (CT) gives them a broad spectrum and slow radiative decay rates (k r ), resulting in poor color purity and significant efficiency roll-off at high current density. [9][10][11][12][13][14][15][16][17][18] Therefore, to achieve high efficiencies, color purities, and device lifetimes in OLEDs, TADFsensitized fluorescent (TSF) OLEDs were developed with TADF material as sensitizing host for conventional fluorescent dopants (CFDs) that were proposed by Prof. Duan and Prof. Adachi.…”

Recent endeavors and perspectives in developing solution-processable host materials for thermally activated delayed fluorescence organic light-emitting diodes

“…15–23 Solution processing is highly advantageous over vacuum processing owing to the easy processability and usage of low-cost instruments such as spin-coating, blade-casting, and inkjet printing in the former, while avoiding harsh fabrication conditions such as high temperature and pressure. Despite significant progress in the development of solution-processed OLEDs, 24–66 their efficiency and lifetimes still lag behind those of vacuum-processed devices.…”