Blue Thermally Activated Delayed Fluorescence Emitters Research Articles

De(sulfon)amidative Cyclization: The Synthesis of Dibenzolactams and Dibenzosultams for Organic Light Emitting Diode Materials

This study addresses a challenge in organic synthetic chemistry: the direct cleavage of amide bonds, which is typically hampered by the thermodynamic stability of the C(Ar)–C(acyl) bond. Previous methods often rely on “CO” extrusion‐jointing transition metal‐catalyzed process and require activated tertiary amides, limiting their applicability due to incompatibility with reactive functional groups such as halogens. Herein, we report a transition metal‐free approach for the deamidative cyclization of biaryl diamides via a radical process, yielding dibenzolactam derivatives. Along this line, we have developed the desulfonamidative cyclization of biaryl disulfonamides to produce dibenzosultams through direct nucleophilic aromatic substitution, demonstrating high selectivity for unsymmetrical structures. Additionally, unsymmetrical sulfamoyl biaryl amides, containing both amide and sulfonamide functionalities, can selectively undergo desulfonamidative coupling with the amide to form dibenzolactams, which offers a complementary synthetic pathway to unsymmetric dibenzolactams. These protocols exhibit excellent compatibility with reactive functional groups, including halogens, providing an innovative synthetic toolbox for the development of thermally activated delayed fluorescence (TADF) materials used in organic light emitting diodes (OLEDs). DMAC‐PDO, incorporating a dibenzolactam as the acceptor unit, serves as an efficient blue TADF emitter with a maximum external quantum efficiency (EQEmax) of 23.4%.

De(sulfon)amidative Cyclization: The Synthesis of Dibenzolactams and Dibenzosultams for Organic Light Emitting Diode Materials.

This study addresses a challenge in organic synthetic chemistry: the direct cleavage of amide bonds, which is typically hampered by the thermodynamic stability of the C(Ar)-C(acyl) bond. Previous methods often rely on "CO" extrusion-jointing transition metal-catalyzed process and require activated tertiary amides, limiting their applicability due to incompatibility with reactive functional groups such as halogens. Herein, we report a transition metal-free approach for the deamidative cyclization of biaryl diamides via a radical process, yielding dibenzolactam derivatives. Along this line, we have developed the desulfonamidative cyclization of biaryl disulfonamides to produce dibenzosultams through direct nucleophilic aromatic substitution, demonstrating high selectivity for unsymmetrical structures. Additionally, unsymmetrical sulfamoyl biaryl amides, containing both amide and sulfonamide functionalities, can selectively undergo desulfonamidative coupling with the amide to form dibenzolactams, which offers a complementary synthetic pathway to unsymmetric dibenzolactams. These protocols exhibit excellent compatibility with reactive functional groups, including halogens, providing an innovative synthetic toolbox for the development of thermally activated delayed fluorescence (TADF) materials used in organic light emitting diodes (OLEDs). DMAC-PDO, incorporating a dibenzolactam as the acceptor unit, serves as an efficient blue TADF emitter with a maximum external quantum efficiency (EQEmax) of 23.4%.

85‐3: Machine Learning Strategy Towards Inverse Design of Blue TADF Emitter: Training Excited State Properties Based on Density Functional Theory Calculations

We introduce inverse design strategy utilizing machine learning (ML) models to discover efficient blue thermally activated delayed fluorescence (TADF) organic emitter materials. Here, we leverage graph neural network (GNN) to predict the characteristic intrinsic materials properties of TADF such as excited state energy levels and their transition properties. The GNN model is trained based on density‐functional theory (DFT) calculation results to meet the TADF properties. We discuss consistency between experimental observation and ML predictions, and examined conditions for improving the accuracy of DFT calculations and ML models on top of it.

Fine tuning of excited states by trifluoromethylphenyl for blue-shifted color and enhanced EQEs in thermally activated delayed fluorescence emitters

3,6-di-tert-butyl-9H-carbazole and 3,6-diphenyl-9H-carbazole have been widely used to construct blue thermally activated delayed fluorescence (TADF) emitters. However, it is difficult for related emitters to achieve maximum external quantum efficiency (EQEmax) above 20 % with the Commission Internationale de l'Eclairage (CIE) y ≤ 0.12. A new type of donor was developed to construct blue TADF molecules, namely CF3P-BuCz-TRZ and CF3P-PhCz-TRZ. The weak electron-withdrawing trifluoromethylphenyl (CF3P) with moderate steric hindrance was introduced into the 1-site of carbazole donor for improving the color purity for blue TADF emitters. More importantly, the introduction of CF3P tightly compacts the energy levels for the significant excited states in RISC process. The energy gap between the lowest singlet excited (S1) state and the lowest triplet (T1) state (Δ E(S1−T1)), as well as between T1 and the higher triplet (Tn, n ≥ 2) states (Δ E(Tn−T1)) were reduced, so that Tn (n ≥ 2) could be effectively harvested to further promote reverse intersystem crossing (RISC). As a result, the OLEDs based on CF3P-BuCz-TRZ and CF3P-PhCz-TRZ displayed blue electroluminescence with CIE coordinates of (0.156, 0.107) and (0.155, 0.115). In particular, the maximum EQEs of the CF3P-PhCz-TRZ device reached 20.43 % without employing any light out-coupling enhancement or TADF-sensitized structure. This strategy should be valuable for designing more pure-blue and deep-blue TADF emitters.

Structure Engineering of Acridine Donor to Optimize Color Purity of Blue Thermally Activated Delayed Fluorescence Emitters.

9,9-Dimethyl-9,10-dihydroacridine (DMAC) is one of the most widely used electron donor for constructing high-performance thermally activated delayed fluorescence (TADF) emitters. However, DMAC-based emitters often suffer from the imperfect color purity, particularly in blue emitters, due to its strong electron-donating capability. To modulate donor strength, 2,7-F-Ph-DMAC and 2,7-CF3-Ph-DMAC were designed by introducing the electron-withdrawing 2-fluorophenyl and 2-(trifluoromethyl)phenyl at the 2,7-positions of DMAC. These donors were used, in combination with 2,4,6-triphenyl-1,3,5-triazine (TRZ) acceptor, to develop novel TADF emitters 2,7-F-Ph-DMAC-TRZ and 2,7-CF3-Ph-DMAC-TRZ. Compared to the F- or CF3-free reference emitter, both two emitters showed hypsochromic effect in fluorescence and comparable photoluminescence quantum yields without sacrificing the reverse intersystem crossing rate constants. In particular, 2,7-CF3-Ph-DMAC-TRZ based OLED exhibited a blue shift by up to 39 nm and significantly improved Commission International de l'Éclairage (CIE) coordinates from (0.36, 0.55) to (0.22, 0.41), while the external quantum efficiency kept stable at about 22.5 %. This donor engineering strategy should be valid for improving the color purity of large amount of acridine based TADF emitters. It can be predicted that pure blue TADF emitters should be feasible if these F- or CF3-modifed acridine donors are combined with other weaker electron acceptors.

Asymmetric phosphorylation integrating host feature and blue thermally activated delayed fluorescence of thiaxanthene S,S-dioxide emitter for efficient heavily doped white organic light-emitting diodes

Significant efforts have been recently devoted to develop simply structured white organic light-emitting diodes (WOLEDs) based on purely thermally activated delayed fluorescence (TADF) with a single-emissive-layer and heavy-doping configuration. Herein, through introducing a diphenylphosphine oxide group on thiaxanthene S,S-dioxide acceptor, we integrate host characteristics to blue TADF emitter CZ-MPSPO, which is beneficial to balanced exciton allocation and quenching suppression in single emissive layers of TADF WOLEDs for high performance. After co-doping with a conventional yellow TADF emitter, TADF performance of CZ-MPSPO is preserved, but external quantum efficiencies (EQE) of WOLEDs are remarkably improved through the synergistic singlet and triplet exciton harvesting by CZ-MPSPO and 4CzTPNBu. The steric hindrance of CZ-MPSPO also mitigates emission quenching by 4CzTPNBu, leading to the favourable EQE up to ∼20 % of single-EML pure TADF WOLEDs with the doping concentration of CZ-MPSPO as high as 70 %.

The novel thermally activated delayed fluorescence compounds based on trifluoromethylpyridine were synthesized for blue OLEDs

Seeking efficient blue thermally activated delayed fluorescence (TADF) luminous materials with a simple structure and applying them to organic light-emitting diodes (OLEDs) is still an urgent challenge. Herein, two novel D-π-A type blue TADF emitters with simple molecular structure, namely p-AcBPyCF3 and m-AcBPyCF3, featuring a trifluoromethylpyridine (PyCF3) as acceptor moiety, 9,9-dimethyl-tetrahydroacridine (Ac) as donor unit and benzene (B) as π-bridge, respectively, are first developed and compared in parallel. The analysis of single crystal reveals that p-AcBPyCF3 possesses clearly twisted geometry between the donor and acceptor units, as well as expanded molecular rigidity, thus leading to a smaller singlet-triplet energy difference and greatly improved emission efficiency. The p-AcBPyCF3 exhibits a photoluminescence quantum yield (PLQY) of 28.80 %, surpassing the PLQY value of 18.70 % for the m-AcBPyCF3. Compared to m-AcBPyCF3, the TADF-OLEDs based on p-AcBPyCF3 demonstrated exceptional properties, which suppresses the rotation of molecular conformation and can achieve high PLQY by reducing non radiative transformation processes, resulting in a maximum external quantum efficiency (EQE) of 9.26 % with peak at 470 nm and blue color coordinates of (0.18, 0.25). This work highlights that the simple PyCF3 group can be a promising electron acceptor moiety for the design of blue TADF materials.

Efficient Blue Thermally Activated Delayed Fluorescence Molecules with Sandwich‐Structured Through‐Space Charge Transfer for Fabricating High‐Performance OLEDs

AbstractExploring robust blue luminescent materials is of high significance but challenging for the commercialization application of organic light‐emitting diodes (OLEDs). In this work, it is wished to report two blue thermally activated delayed fluorescence (TADF) molecules with a through‐space charge transfer feature. They have sandwich‐structured molecular backbones comprised of one triphenyltriazine acceptor and two 9‐phenylcarbazole or 3,6‐di(tert‐butyl)‐9‐phenylcarbazole donors that are linked at the 1,8,9‐positions of a 3,6‐di(tert‐butyl)carbazole holder, and exhibit high thermal stability and strong blue delayed fluorescence with high photoluminescence quantum yields and fast reverse intersystem crossing. The blue OLEDs use 2TBCTC as an emitter and provide outstanding maximum external quantum efficiencies (EQEmaxs) of up to 32.76% with Commission Internationale de I'Eclairage coordinates of (0.160, 0.206). To the best of knowledge, 2TBCTC is the most efficient blue TADF emitter based on through‐space charge transfer in the literature. Moreover, the interlayer‐sensitizing OLED employs 2TBCTC as a sensitizer for blue multi‐resonance TADF (MR‐TADF) molecule (v‐DABNA) as guest emitter attains an excellent EQEmax of 32.69% with a narrow full width at half maximum of 18 nm, validating the excellent potential of 2TBCTC as sensitizer for MR‐TADF emitters and the feasibility and effectiveness of the interlayer sensitization strategy for blue hyperfluorescence OLEDs.

Unravelling the impact of sulfur atom oxidation and donor–acceptor effects on the performance of blue TADF emitters: a detailed computational study

Blue thermally activated delayed fluorescence (TADF) materials with substantial donors and acceptors skeleton for OLEDs.

Exploration of violet-to-blue thermally activated delayed fluorescence emitters based on "CH/N" and "H/CN" substitutions at diphenylsulphone acceptor. A DFT study.

The violet-to-blue thermally activated delayed fluorescence (TADF) emitters were created employing several substituents based on 5,5-dimethyl-5,10-dihydropyrido [2,3-b][1,8] naphthyridine-diphenylsulphone (DMDHPN-DPS) called 1a via "CH/N" and "H/CN" substitutions at the diphenylsulphone acceptor (DPS) moiety. The parent compound 1a was selected from our former work after extensive research employing "CH/N" substitution on Dimethyl-acridine (DMAC) donor moiety. There is a little overlap amid the highest occupied molecular orbitals (HOMOs) and lowest un-occupied molecular orbitals (LUMOs) due to the distribution of HOMOs and LUMOs primarily on the DMDHPN donor and the DPS acceptor moieties, respectively. It resulted in a narrower energy gap (∆E ST) between the lowest singlet (S1) and triplet (T1) excited state. In nearly all derivatives, the steric hindrance results in a larger torsional angle (85°-98°) between the plane of the DMDHPN and the DPS moieties. The predicted ΔE ST values of the compounds with "H/CN" substitution were lower than those of the comparable "CH/N" substituents, demonstrating the superiority of the reversible inter-system crossing (RISC) from the T1 → S1 state. All derivatives have emission wavelengths (λ em) in the range of 357-449nm. The LUMO → HOMO transition energies in the S1 states are lowered by the presence of -CN groups or -N = atoms at the ortho or meta sites of a DPS acceptor unit, causing the λ em values to red-shift. Furthermore, the λ em showed a greater red-shift as there were more-CN groups or -N = atoms. Three of the derivatives named 1b, 1g, and 1h, emit violet (394nm, 399nm, and 398nm, respectively), while two others, 1f and 1i, emit blue shade (449nm each) with reasonable emission intensity peak demonstrating that these derivatives are effective violet-to-blue TADF nominees. The lower ΔE ST value for derivative 1i (0.01eV) with λ em values of 449nm make this molecule the finest choice for blue TADF emitter amongst all the studied derivatives. We believe our research might lead to the development of more proficient blue TADF-OLEDs in the future.

Tuning photophysical properties of bicarbazole-based blue TADF emitters with AIE feature: Trade-off between small singlet-triplet energy splitting and high photoluminescence quantum yield

Three aggregation-induced emission (AIE) and thermally activated delayed fluorescence (TADF) blue light-emitting materials were successfully synthesized using bicarbazole and phenylsulfonyl/benzophenone moieties as electron donors and acceptors, respectively, via Buchwald-Hartwig reaction. Density functional theory calculations showed that the three emitters have a moderate dihedral angle between the two carbazole planes and between the donor and acceptor, resulting in a good conjugated structure and a trade-off between the small ΔEST and high photoluminescence quantum yield of the BCzDPM molecule. The cyclic voltammetry, thermogravimetric analysis and differential scanning calorimetry tests demonstrated that the three materials had high electrochemical and thermal stability. The three emitters exhibited obvious intramolecular charge transfer characteristics in solution and film. According to the fluorescence and low-temperature phosphorescence spectra, the lowest singlet and triplet excited state energy levels of BCzDPM were 2.96 eV and 2.78 eV, respectively, with a ΔEST of 0.18 eV. Using these emitters as non-doped emissive layers, efficient blue electroluminescent devices were fabricated. The maximum current efficiency and external quantum efficiency reached 15.4 cd/A and 7.05% for the BCzDPM device, respectively, and the efficiency roll-off of BCzDPM was smaller than that of PSOBCz and PBCzPM, under high current density.

Longevity gene responsible for robust blue organic materials employing thermally activated delayed fluorescence

The 3rd-Gen OLED materials employing thermally-activated delayed fluorescence (TADF) combine advantages of first two for high-efficiency and low-cost devices. Though urgently needed, blue TADF emitters have not met stability requirement for applications. It is essential to elucidate the degradation mechanism and identify the tailored descriptor for material stability and device lifetime. Here, via in-material chemistry, we demonstrate chemical degradation of TADF materials involves critical role of bond cleavage at triplet state rather than singlet, and disclose the difference between bond dissociation energy of fragile bonds and first triplet state energy (BDE-ET1) is linearly correlated with logarithm of reported device lifetime for various blue TADF emitters. This significant quantitative correlation strongly reveals the degradation mechanism of TADF materials have general characteristic in essence and BDE-ET1 could be the shared “longevity gene”. Our findings provide a critical molecular descriptor for high-throughput-virtual-screening and rational design to unlock the full potential of TADF materials and devices.

Highly efficient and low operation voltage hybrid solution-processed WOLEDs based on wide FWHM blue TADF and red phosphorescent emitters

Recent developments in the field of thermally activated delayed fluorescence (TADF) emitter have led to significantly improved performances of hybrid solution processing prepared white organic light-emitting diodes (s-WOLEDs). Importantly, wide coverage of electroluminescent spectra and balanced transfer of carriers are conclusive factors to obtain high quality lighting sources. This paper demonstrated high quality s-WOLEDs grounded on blue TADF and red phosphorescent emitters. In optimal WOLED, Förster energy transfer (ET) distance and ET rate were calculated to be 1.81 nm and 1.29 × 106 s−1, respectively. Also, exciplex host were employed to decrease operation voltage and modulate carriers' distribution. The fabricated optimal solution-processed warm white electroluminescence device exhibited high color rendering index of 80 and maximum luminescent efficiencies up to 29.22 cd A−1, 28.68 lm W−1 and 13.5%. Furthermore, the Commission Internationale de I'Eclairage coordinates of this device are (0.39, 0.41) at the current density of 10 mA cm−2, while the turn-on voltage of this device is 3.0 V.

Deep blue thermally activated delayed fluorescent emitters based on methyl-modified acridin-9(10H)-one acceptor

Developing deep blue thermally activated delayed fluorescence (TADF) materials with high efficiencies and good color purities is still a formidable challenge. Here, two novel deep blue TADF emitters, namely MePhCz-AD and MePhCz-AD-Py, were synthesized by incorporating two 3,6-diphenyl-9H-carbazole donors onto the methyl-modified acridin-9(10H)-one (AD) acceptor, respectively. The high rigidity of AD acceptor effectively suppressed non-radiative transition and vibration relaxation of excited states, which is favorable for a good emitting quantum yield and narrow spectral width. The presence of methyl groups at 2,7-sites of AD ring slightly reduced the acceptor strength and contributed to the deep blue emission color. Incorporation of phenyls at 3,6-sites of carbazole ring delocalized the distribution of the highest occupied molecular orbital (HOMO), promoting the radiative decay process. As a result, these two emitters showed deep blue TADF with fast radiative decay rates kR > 107 s−1. In addition, with the introduction of pyridyl (Py) group at 10-site of AD ring instead of phenyl, both the spin-orbital coupling (SOC) constant between high-lying triplet states and the lowest singlet excited state (S1) and thus the reverse intersystem crossing rate constant (kRISC) were dramatically promoted for MePhCz-AD-Py. The organic light-emitting diode with MePhCz-AD-Py as doped emitter exhibited a maximum external quantum efficiency (EQEmax) of 15.4% with a relatively narrow FWHM of 60 nm and the deep-blue color coordinates of (0.15, 0.15).

High-performance single-emitting-layer hybrid white organic light-emitting diodes featuring a stable blue emission component from green thermally activated delayed fluorescence

In this work, we demonstrate single-emitting-layer hybrid white organic light-emitting diodes (WOLEDs) with high-efficiency and low efficiency roll-off. Here, the white emission arises from stable blue emission via electroluminescence (EL) spectral shift from green thermally activated delayed fluorescence (TADF) emitter and yellow phosphorescent emitter. WOLEDs shows a maximum current efficiency of 56.77 cd/A, maximum power efficiency of 50.19 lm/W, and maximum external quantum efficiency of 20.00%. Compared to the devices composed of conventional blue TADF emitters, the device based on EL spectral shift-induced blue emission exhibit higher performances, indicating that efficient white emission can be obtained without a typical blue emitter. Our study provides an alternative way to fabricate high-performance WOLEDs based on EL spectral shift technology.

Rational Molecular Design Strategy for High-Efficiency Ultrapure Blue TADF Emitters: Symmetrical and Rigid Sulfur-Bridged Boron-Based Acceptors.

Developing highly efficient blue thermally activated delayed fluorescence (TADF) emitters with a narrowband emission is still a challenge. Here, novel ultrapure blue TADF emitters of TSBA-Cz and TSBA-PhCz were designed and synthesized for organic light-emitting diodes (OLEDs). Photophysical and time-dependent density functional theory calculation results simultaneously show the similar intramolecular charge-transfer character of MR-type TADF emitters. Benefiting from the symmetrical and rigid molecular configuration, compounds TSBA-Cz and TSBA-PhCz emit a pure blue emission peak at 463 and 470 nm, a narrow full width at half-maximum (FWHM) of 30 and 36 nm, and a small singlet-triplet energy gap (ΔEST) of 0.21 and 0.18 eV, respectively, facilitating their excellent TADF behavior in doped films. Furthermore, highly efficient TADF-OLED devices using the TSBA-Cz and TSBA-PhCz with external quantum efficiencies of 23.4 and 21.3% emit ultrapure blue electroluminescence (EL) at 464 and 472 nm with a narrow FWHM of about 35 nm and CIE color coordinates of (0.14, 0.11) and (0.12, 0.18). This work provides novel TADF emitters for blue OLEDs with narrowband EL.

Spiral donor-based host materials for highly efficient blue thermally activated delayed fluorescence OLEDs

Spiral donor units have attracted extensive research focuses in designing highly emissive thermally activated delayed fluorescence (TADF) emitters. Herein, to reveal the significance of spiral donor units for constructing highly efficient host materials, several spiral donor-based host materials are developed. With the incorporation of spiral donor, increased intermolecular distance is achieved to reduce the concentration quenching effect of dopant. Moreover, the high triplet energy level of spiral donor can provide an additional energy transfer channel to further improve the device performance. Noteworthy, by connecting spiral donors or conventional carbazole unit with different electron-withdrawing units phenoxathiine 10,10-dioxide (PX) or phenoxathiine (PA), these hosts are given different photophysical properties of TADF, room-temperature phosphorescence (RTP) and conventional fluorescence (CF). The strong electron-withdrawing ability of PX is beneficial to the TADF character of spiral donor-based molecules, while the weak electron-withdrawing ability of PA is beneficial to the RTP property. Consequently, the blue OLEDs with DspiroAc-TRZ as a dopant emitter based on the hosts with TADF characters exhibit higher performance than those with RTP and CF properties, and excellent external quantum efficiency (EQE) of 36.1 % and current efficiency of 84.6 cd/A are achieved in a simple device structure. Furthermore, peak EQEs of 34.0 % and 33.0 % are achieved, when DspiroS-PX and DspiroS-PA hosted DspiroAc-TRZ are used to sensitize blue multi-resonance TADF emitter v-DABNA. Our work may shed new light on designing highly efficient host materials for TADF emitters.

Tailoring Donor‐Acceptor Emitters to Minimise Localisation Induced Quenching of Thermally Activated Delayed Fluorescence

AbstractBy inverting the common structural motif of thermally activated delayed fluorescence (TADF) materials to a rigid donor core and multiple peripheral acceptors, it has been shown possible to achieve both a reverse intersystem crossing (rISC) rate 1×107 s−1 and a unity photoluminescence quantum yield [Dos Santos et al. Adv. Sci. 5 (2018) 1700989]. However, the rISC rate in this motif is quenched by localisation of the excited state electronic structure which causes in‐equivalence between the peripheral acceptors. In this paper, we explore a series of related molecular targets which seek to reduce the effect of localisation on the rISC rates. This includes structures that contain donors exhibiting three‐fold or four‐fold symmetry and different degrees of steric hindrance around the donor‐acceptor bond with the objective of using steric hindrance to exert finer conformational control of the excited state dynamics to enhance functional properties. We demonstrate that a triazatruxene central donor is most effective for TADF owing to the energetic position of the locally excited state, while cyano‐benzonitriles are the most effective acceptors for reducing the effect of localisation on the electronic structure. These also push the emission into the blue region of the spectrum, opening the possibilities for this to be a pathway to develop efficient blue TADF emitters.

Towards Efficient Blue Delayed-Fluorescence Molecules by Modulating Torsion Angle Between Electron Donor and Acceptor

Towards Efficient Blue Delayed-Fluorescence Molecules by Modulating Torsion Angle Between Electron Donor and Acceptor

Interfacial Exciplex Host to Release Interfacial Accumulated Charges for Highly Efficient and Bright Solution‐Processed White Organic Light‐Emitting Diodes

AbstractWhite organic light‐emitting diodes (WOLEDs) have attracted extensive attention and are considered as an ideal next‐generation lighting source. However, maintaining high efficiency and high color rendering index (CRI) in WOLEDs still faces great challenges. The charges accumulation at the interface leads to nonradiative recombination and further Joule heat, which is a source of efficiency decrease and device degradation. In this paper, the interfacial exciplex is designed as the host for high efficiency; the blue thermally activated delayed fluorescence (TADF) material and the red phosphorescent material are employed as guests for high CRI. Due to the interfacial exciplex host, electrons don't need to overcome the potential barrier to inject into the light‐emitting layer, but can directly compound with holes at the interface, so as to release the interfacial accumulated charges and improve the recombination efficiency of carriers. Also, a suitable energy level gradient for hole injection transmission is constructed. Finally, WOLEDs with a current efficiency of 52.8 cd A−1, an external quantum efficiency of 22.9 %, the Commission Internationale de I'Eclairage (CIE) coordinate of (0.35,0.39), and the high CRI of 80 are obtained, which are the highest values ever achieved by the solution processed WOLEDs based on blue TADF emitters.