A Simple Organic Molecule Realizing Simultaneous TADF, RTP, AIE, and Mechanoluminescence: Understanding the Mechanism Behind the Multifunctional Emitter.

Aggregation-induced emission (AIE), thermally activated delayed fluorescence (TADF), room-temperature phosphorescence (RTP), and mechanoluminescence (ML) have attracted widespread interest. However, a multifunctional organic emitter exhibiting simultaneous AIE, TADF, RTP, and ML has not been reported. Now, two multifunctional blue emitters with very simple structures, mono-DMACDPS and Me-DMACDPS, exhibit typical AIE, TADF, and RTP properties but different behavior in mechanoluminescence. Crystal structure analysis reveals that large dipole moment and multiple intermolecular interactions with tight packing mode endow mono-DMACDPS with strong ML. Combined with the data of crystal analysis and theoretical calculation, the separated monomer and dimer in the crystal lead to the typical TADF and RTP properties, respectively. Simple-structure mono-DMACDPS is the first example realizing TADF, RTP, AIE, and ML simultaneously.

Star-Shaped Macromolecules with the Core of Hexakis-(fluoren-2-yl)benzene and the Periphery of Pyridine: Synthesis and Application as Solution-Processable Electron-Transport Materials.

Three new star-shaped macromolecules with hexakis(fluoren-2-yl)benzene as the core and pyridine as the periphery (2Py-HFB, 3Py-HFB, and 4Py-HFB) are synthesized and characterized. The synthetic conditions of octacarbonyldicobat-catalyzed cycloaddition reaction for different alkyne precursors are investigated. The coordination interaction between the pyridine ring of alkyne precursor and the cobalt catalyst may result in very low yield of the cyclotrimerization product. However, with the increase of the catalyst loading, the yields of the intermediates of cyclopentadienone are enhanced. Then, the desired cyclotrimerization products can be obtained by the Diels-Alder reactions of cyclopentadienone with acetylene in good yield. These new compounds exhibit good thermal stability and favorable electron affinity. By using the new compounds as electron-transporting materials, all-solution-processed phosphorescent organic light-emitting devices (OLEDs) show good performance with a maximum current efficiency of 5.6 cd A(-1) and maximum external quantum efficiency of 4.68%.

Fused tetracyclic tris[1,2,4]triazolo[1,3,5]triazine as a novel rigid electron acceptor for efficient thermally activated delayed fluorescence emitters.

Tris[1,2,4]triazolo[1,3,5]triazine, a new acceptor based on a fused triazole and triazine moiety, is utilized to construct D3-A star-shaped tristriazolotriazine derivatives, named 3,7,11-tris(4-(10H-phenoxazin-10 yl)phenyl)tris([1,2,4]triazolo)[1,3,5]triazine (TTT-PXZ) and 3,7,11-tris(4-(9,9-dimethylacridin-10(9H)yl)phenyl)tris([1,2,4])triazolo[1,3,5]triazine (TTT-DMAC). Both TTT-PXZ and TTT-DMAC emitters feature TADF activities and AIEE properties. Consequently, solution processed OLEDs based on TTT-PXZ green emitters exhibited good performances, with an external quantum efficiency (EQE) of up to 6.2%.

Acceptor plane expansion enhances horizontal orientation of thermally activated delayed fluorescence emitters.

Manipulating orientation of organic emitters remains a formidable challenge in organic light-emitting diodes (OLEDs). Here, expansion of the acceptor plane of thermally activated delayed fluorescence (TADF) emitters was demonstrated to selectively modulate emitting dipole orientation. Two proof-of-the-concept molecules, PXZPyPM and PXZTAZPM, were prepared by introducing a planar 2-phenylpyridine or 2,4,6-triphenyl-1,3,5-triazine substituent into a prototypical molecule (PXZPM) bearing a pyrimidine core and two phenoxazine donors. This design approach suppressed the influence of substituents on electronic structures and associated optoelectronic properties. Accordingly, PXZPyPM and PXZTAZPM preserved almost the same excited states and similar emission characteristics as PXZPM. The expanded acceptor plane of PXZPyPM and PXZTAZPM resulted in a 15 to 18% increase in horizontal ratios of emitting dipole orientation. PXZPyPM supported its green device exhibiting an external quantum efficiency of 33.9% and a power efficiency of 118.9 lumen per watt, competitive with the most efficient green TADF OLEDs reported so far.

Simple construction of deep-red hexaazatrinaphthylene-based thermally activated delayed fluorescence emitters for efficient solution-processed OLEDs with a peak at 692 nm.

Two solution-processable deep-red thermally activated delayed fluorescence emitters based on a 5,6,11,12,17,18-hexaazatrinaphthylene acceptor core were developed through a simple and catalyst-free nucleophilic substitution reaction. The solution-processed OLEDs using these emitters achieved a peak external quantum efficiency of 4.8% with the emission peak at 692 nm.

Fused twin-acridine scaffolds as electron donors for thermally activated delayed fluorescence emitters: controllable TADF behavior by methyl substitution.

Fused twin-acridine scaffolds of TMQAC and MeTMQAC were designed as novel donors to construct new organic emitters. TMQAC-based emitters were TADF active, while the TADF character was turned off in MeTMQAC-based emitters by the extra methyl group. The TMQAC-based emitters exhibited high OLED performances, with external quantum efficiencies (EQEs) of up to 20.7%.

Feasible Modification of PEDOT:PSS by Poly(4-styrenesulfonic acid): A Universal Method to Double the Efficiencies for Solution-Processed Organic Light-Emitting Devices.

A feasible, universal, and low-cost strategy for solution-processed organic light-emitting diodes (OLEDs) was provided to significantly enhance the electroluminescent performances. The commercially available poly(4-styrenesulfonic acid) (PSSA) aqueous solution was mixed into poly(styrene sulfonic acid)-doped poly(3,4-ethylenedioxythiphene) (PEDOT:PSS) to modify its chemical and physical properties. The corresponding work function can be easily elevated from 5.04 to 5.63 eV. The modification of PEDOT:PSS by PSSA is found to be a universal method to demonstrate highly efficient OLEDs with different solution-processed host/emitter combinations, covering phosphorescent and thermally activated delayed fluorescence devices. The benchmarking solution-processed OLEDs based on 2,4,5,6-tetrakis(carbazol-9-yl)-1,3-dicyanobenzene and bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) achieved the maximum external quantum efficiencies of 26.6 and 22.4%, respectively, simply by modifying PEDOT:PSS with PSSA, corresponding to the improvement factors of 2.7 and 2.2. It is confirmed that such performances originate simultaneously from reduced interfacial fluorescence quenching, elevated work function, and reduced lateral conduction of the commonly used PEDOT:PSS (Clevios P VP Al 4083).