Optimizing Charge Transfer and Out‐Coupling of A Quasi‐Planar Deep‐Red TADF Emitter: towards Rec.2020 Gamut and External Quantum Efficiency beyond 30 %

Abstract

Herein, we report a deep‐red TADF emitter pCNQ–TPA, composed of quinoxaline‐5,8‐dicarbonitrile (pCNQ) acceptor and triphenylamine (TPA) donor. pCNQ–TPA supported its OLED with desired CIE coordinates of (0.69, 0.31) and the record maximum external quantum efficiency of 30.3 %, which is the best red TADF diode with Rec.2020 gamut for UHDTV. It is showed that through tuning pCNQ–TPA doping concentration, intra‐ and inter‐molecular charge transfer are balanced to synchronously improve emission color saturation and TADF radiation, and remedy aggregation‐induced quenching, rendering photoluminescence quantum yield (PLQY) reaching 90 % for deep‐red emission peaked at ≈690 nm. Quasi‐planar structure further endows pCNQ–TPA with an improved horizontal ratio of emitting dipole orientation, which increases light out‐coupling ratio to 0.34 for achieving the state‐of‐the‐art device efficiencies.

Thermally Activated Delayed Fluorescence Material: An Emerging Class of Metal‐Free Luminophores for Biomedical Applications

“…Typically, the distinct optical and electronic properties of TADF materials could be attributed to the sufficiently small ΔE ST between the S 1 and T 1 states, enabling an efficient RISC process and a resultant ≈100% internal QE by harvesting both singlet and triplet excitons, which is a crucial theoretical breakthrough in organic electronics. [34][35][36][37][38][39][40] Likewise, such unique optical properties render TADF materials as promising candidates for biomedical applications. Generally, two types of luminescence mechanisms are represented in TADF: the prompt fluorescence (PF) and the delayed fluorescence (DF), which could be triggered by photoexcitation or electroexcitation.…”

Highly Efficient and Stable Blue Organic Light‐Emitting Diodes based on Thermally Activated Delayed Fluorophor with Donor‐Void‐Acceptor Motif

“…[ 15 ] On the basis of this molecular design concept, a number of D‐A type TADF materials have been developed and exhibited remarkable performances. [ 16 , 17 ] Nevertheless, owing to the strong electronic interactions between the D and A moieties, these D‐A motifs always lead to clear redshifted emissions, making it difficult to achieve blue emission. [ 14 ] Specifically, both inducive effect and conjugative effects exist between D and A groups, as illustrated in Scheme 1 .…”

Rational Design and Facile Synthesis of Dual‐State Emission Fluorophores: Expanding Functionality for the Sensitive Detection of Nitroaromatic Compounds

“…[43] It is well known that TPA is not only an electron-rich group, but also an active rotor. [53,54] To study the relationship between the motion of rotor and the emission behavior of compounds 4 a-4 f, we further investigated the dependences of the fluorescence properties of 4 a-4 f on solvent viscosity according to the reported method. [55] As shown in Figures S61-66, the maximum emission peak of 4 a-4 d is dramatically decreased with a slight redshifted in highly viscous solvent relative to that in less-viscous solvent.…”