Thermally activated delayed fluorescence carbazole‐triazine dendrimer with bulky substituents

Abstract

Carbazole‐triazine dendrimers with a bulky terminal substituent were synthesized, and the thermally activated delayed fluorescence (TADF) property was investigated. Compared to unsubstituted carbazole dendrimers, dendrimers with bulky terminal substituents showed comparable to better photoluminescence quantum yields (PLQY) in neat films. Phenylfluorene (PF)‐substituted dendrimers showed the highest PLQY of 81%, a small ΔEst of 0.06 eV, and the fastest reverse intersystem crossing (RISC) rate of ∼1 × 105 s−1 compared to other dendrimers. Phosphorescence measurements of dendrimers and dendrons (fragments) indicate that the close proximity of the triplet energy of phenylfluorene‐substituted carbazole dendrons (3LE) to that of phenylfluorene‐substituted dendrimers (1CT, 3CT) contributes to RISC promotion and improves TADF efficiency. Terminal modification fine‐tunes the energy level and suppresses intermolecular interactions, and this study provides a guideline for designing efficient solution‐processable and non‐doped TADF materials.

Introducing Internal Host Component to Thermally Activated Delayed Fluorescence Emitter for Efficient NIR Nondoped Organic Light-Emitting Diodes

“…These efficiencies are far inferior to those with mildly doped emitting layers (EMLs), revealing that severe concentration quenching occurs in nondoped EMLs due to the lack of insufficient dilution of the host matrix. While this issue can be universally addressed by introducing suitable sterically shielded groups in terms of molecular design, which can sufficiently enhance the interchromophore distance, this approach significantly weakens/disrupts interchromophore interactions and thus reduces the emission red-shift range via concentration modulation. − Therefore, such intrinsic red TADF emitters can hardly reach beyond the visible region even under nondoped conditions. The development of new molecular modulation strategies is highly desirable for enabling intrinsic red TADF emitters to achieve high-efficiency NIR OLEDs using highly doped/nondoped EMLs. − …”

Aluminum Complex-Core Carbazole Dendrimers Exhibiting Thermally Activated Delayed Fluorescence

“…Carbazole dendrimers have been extensively studied because their highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) separated unique electron distribution matches the design principle of TADF materials . In previous reports, we have demonstrated that the terminal structure strongly influences the TADF properties of carbazole dendrimers through the fine-tuning of the energy levels. , In addition, many of the relevant reports focus on changing the electron-accepting moiety as a core of the carbazole dendrimer. Among them, TADF-type carbazole dendrimer materials utilizing Cu and Au complexes as the central core have also been reported. , Metal complex-core carbazole dendrimers consist of a light-emitting core, dendrons (branches), and surface groups.…”

Chiral‐Guest Induced Multicolor‐Tunable Circularly Polarized Room Temperature Phosphorescence

“…due to their long luminescence lifetime, low biological toxicity, and strong modifiability. [ 1–12 ] With the development of strategies such as introducing heavy atoms, molecular design engineering, and host–guest doping, a large number of organic materials with excellent phosphorescence properties have been developed. [ 13–20 ] Although the phosphorescence performance of organic materials has been greatly improved, constructing organic phosphorescence materials with special functionalities still faces great challenges.…”