Triphenylamine‐Functionalized Multiple‐Resonance TADF Emitters with Accelerated Reverse Intersystem Crossing and Aggregation‐Induced Emission Enhancement for Narrowband OLEDs

Abstract

Multiple-resonance (MR) thermal activated delayed fluorescence (TADF) emitters have attracted increasing attention in organic electroluminescence devices, owing to their superior quantum efficiency and narrowband emission for high color purity. However, MR-TADF materials often suffer from severe aggregation-caused quenching (ACQ) and efficiency roll-off problems due to their rigid planar structures and the lack of sufficient charge-transfer (CT) characters with inefficient reverse intersystem crossing (RISC). Herein, by attaching electron-rich triphenylamine (TPA) with twisted spatial conformation to the MR framework, two efficient narrowband MR-TADF emitters, namely BNCz-pTPA and BNCz-mTPA, are developed. The TPA substituent endows the new emitters with aggregation-induced emission enhancement (AIEE) for ACQ suppression. The unprecedented AIEE-MR-TADF emitters exhibit CT character in high-lying triplet excited states for faster RISC, while the locally-excited (LE) character of the first singlet excited state is retained for narrowband emission with high emission efficiency. An organic light-emitting diode (OLED) based on BNCz-pTPA exhibits a maximum external quantum efficiency of 27.3%with slow efficiency roll-off, demonstrating much higher performances than those of the BNCz-based OLED. This study may provide a simple but effective approach to constructing high-performance emitters for wide-colorgamut OLED displays.

Rational Multidimensional Shielded Multiple Resonance Emitter Suppresses Concentration Quenching and Spectral Broadening for Solution-Processed Organic Light-Emitting Diodes

“…However, as f w increases above 50%, a relatively weak and broad emission peak is observed due to the turbidity of the solution. 40 This result may endow a high performance of 6TBN under nondoped conditions. The TADF character is demonstrated by transient photoluminescence decay curves (TRPL, Figure 3d), and it can be seen 6TBN exhibits a short prompt fluorescence (τ p ) and long delayed fluorescence (τ d ) of 19.5 ns and 50.9 μs, respectively, under an N 2 atmosphere at room temperature.…”

“…The emission intensity increases with more water content and reaches a maximum at water fractions ( f w ) of 30%. However, as f w increases above 50%, a relatively weak and broad emission peak is observed due to the turbidity of the solution . This result may endow a high performance of 6TBN under nondoped conditions.…”

Aggregation‐induced narrowband isomeric fluorophores for ultraviolet nondoped OLEDs by engineering multiple nonbonding interactions

“…Further increasing f w to 90%, the PL intensity of them present an obvious declining trend along with a slight blue-shift of emission peaks, possibly due to the twisted intramolecular charge transfer process. [29][30][31] When increasing the f w from 90% to 99%, the emission intensity of o-DCz-Pm is enhanced, showing an atypical aggregation enhanced emission (AEE) characteristic, [32][33][34][35] which could be due to the formation of stable nanoparticles that prevent the interactions between molecules and water (Figure S4b). As for m-DCz-Pm, even if there is a slight rise at f w of ≈60% comparable to that in THF solution, AEE phenomenon is inconspicuous.…”

Monomer Emission Mechanism Research of Tetraphenylethene Derivative with Supramolecular Self-Assembly in Polymer Microspheres

“…The photophysical phenomenon “aggregation-induced emission” (AIE) was coined by Tang’s group in 2001 and obtained increasing academic interest in various scientific fields ever since . Multifunctional applications constructed from AIE luminogens (AIEgens) have been developed for organic light-emitting diodes (OLEDs), , biomedical imaging, , photothermal therapy, , etc. The AIEgens usually are non-emissive as isolated molecules but emit strongly when aggregated, which is opposite to the aggregation-caused quenching (ACQ) phenomenon .…”