Structural Design of Blue‐to‐Red Thermally‐Activated Delayed Fluorescence Molecules by Adjusting the Strength between Donor and Acceptor

Abstract

Owing to the faster response time, wider viewing angle and thinner thickness of organic light emitting diodes (OLEDs) than the conventional displays, the development of high‐efficiency light‐emitting materials has become the focus of attention. In recent years, the TADF materials have aroused widespread attention and experienced rapid development as an emitter in OLEDs, since the maximum internal quantum efficiency can reach 100% theoretically. TADF materials have exhibited the potential to be a low‐cost alternative to expensive phosphorescent luminophors. Whereas, the high resolution displays must endow the characteristics of stable and efficient panchromatic emission. The chemical structure of TADF materials are generally composed of electrical donor and acceptor, the emission colors and efficiency can be adjusted by the charge transfer between them. In this paper, TADF emitters with different emission colors are reviewed, accompanied with the investigation on their molecular design strategies and photophysical properties. In addition, the development direction and application of TADF materials are prospected.

Bridge control of photophysical properties in benzothiazole-phenoxazine emitters – from thermally activated delayed fluorescence to room temperature phosphorescence

“…32 This acceptor unit is combined with phenoxazine (PXZ), a strong donor moiety commonly used in the field of TADF as it tends to give rise to stable high-energy triplet states and it has a large dihedral angle with adjacent groups. [33][34][35] To finalise the design, a phenyl, 28 naphthyl, or thienyl group is introduced as a p-bridge between the donor and the acceptor to obtain a clear separation of the highest occupied and lowest unoccupied molecular orbital (HOMO and LUMO, respectively). The starting Scheme 1 Synthesis procedures for the three BTaz-Ar-PXZ emitters: (i) 2-aminothiophenol, sodium metabisulfite, DMF, reflux, 2 h; (ii) Pd(OAc) 2 , 10Hphenoxazine, (t-Bu) 3 P, NatBuO, toluene, reflux, 16 h. materials for the dyad synthesis are the three respective aromatic bridge molecules substituted with a bromine and an aldehyde group on the appropriate positions.…”

Diazine-based thermally activated delayed fluorescence chromophores

“…In this context, development of a third generation OLEDbased on TADF chromophores appears as a promising alternative. 1,2,18,19 In addition to high stability and high luminance efficiency along with metalfree composition, all-organic TADF emitters allow production of a stable deep-blue light, which has always been problematic for the second-generation OLEDs. 20 In this context, theoretical studies using quantum mechanics and especially Density Functional Theory (DFT) and its Time-Dependent version (TD-DFT) have shown their effectiveness to contribute to the understanding of the relationship between molecular structure and TADF features, but also for tailored molecular engineering.…”

A reverse intersystem crossing managing assistant dopant for high external quantum efficiency red organic light-emitting diodes

“…The simulated HOMO-LUMO gaps of 4CzTPN, BTCz3CzTPN and 2BTCz2CzTPN were 2.85, 2.75 and 2.71 eV, respectively, which can be interpreted that the BTCz donor decreased the HOMO-LUMO gap. 30 The singlet and triplet energies of 4CzTPN, BTCz3CzTPN and 2BTCz2CzTPN were governed by the BTCz donor. As shown in Fig.…”