Integrating molecular rigidity and chirality into thermally activated delayed fluorescence emitters for highly efficient sky-blue and orange circularly polarized electroluminescence

Ni, Fan; Huang, Chih‐Wei; Tang, Yukun; Chen, Zhanxiang; Wu, Yaxun; Xia, Shengpeng; Cao, Xiaosong; Hsu, Jung-Hsien; Lee, Wei‐Kai; Zheng, Kaiyuan; Huang, Zhongyan; Wu, Chung‐Chih; Yang, Chuluo

doi:10.1039/d0mh01521k

Cited by 83 publications

(30 citation statements)

References 82 publications

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“…The key intermediate of MeIAc was synthesized through a three‐step reaction according to previous reports [9] . The two‐step synthesis of MTBA from this key intermediate is summarized in Figure 1a.…”

Section: Resultsmentioning

confidence: 99%

“…The key intermediate of MeIAc was synthesized through a three-step reaction according to previous reports. [9] The twostep synthesis of MTBA from this key intermediate is summarized in Figure 1a. The first step involves palladium-catalyzed C À N coupling between the commercially available starting materials, 2-(4-iodophenyl)acetonitrile and MeIAc, which proceeded smoothly under reflux conditions to obtain 43 % yield of MABA.…”

Section: Resultsmentioning

confidence: 99%

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Deep‐Red Fluorescence from AIE‐Active Luminophore: High‐Brightness and Wide‐Range Piezochromism**

Yao³

et al. 2022

ChemistrySelect

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Driven by the rapidly increasing demand for intelligent materials, the sensitivity of organic materials to pressure has been intensively investigated in recent years. Many examples describe material responses to both mechanical grinding and hydrostatic pressure, but only few materials have been identified with clear colour difference as well as strong penetrability, especially under high pressure, limiting development of pressure sensors. In this work, an asymmetric luminophore, MTBA was developed by end‐capping a (Z)‐3‐(benzo[c][1,2,5]‐thiadiazol‐4‐yl)‐2‐phenylacrylonitrile (TPAN) core with propeller‐like triphenylamine (TPA) and rigid 12b‐methyl‐5,12b‐dihydroindeno[1,2,3‐kl]acridine (MeIAc) units, revealing aggregation‐induced emission (AIE) behaviour. In high‐pressure and grinding experiments, MTBA exhibits a dramatically large colour difference of up to 164 nm and 112 nm in deep‐red and near‐infrared regions, respectively, for piezochromic performance that is among the best reports for pure organic materials. The experimental and theoretical analyses indicated that the excellent piezochromic performance of MTBA is due to its highly twisty and rigid conformation, which weakens intermolecular π‐π interaction and obstructs emission quenching during compression.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Deep‐Red Fluorescence from AIE‐Active Luminophore: High‐Brightness and Wide‐Range Piezochromism**

Yao³

et al. 2022

ChemistrySelect

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“…For the development of excellent organic CPL molecules, the angle of vectors between μ and m ( θ μ,m ) away from 90° is desirable, and when cos θ μ,m is greater than 0, the chiral signal presents a positive signal, otherwise a negative signal . The g value can be calculated by the following formula: The estimated μ and m values of R / S -BDTPA are 1.52 × 10 –18 and 1.18 × 10 –19 esu·cm, respectively; the calculated θ μ,m of R / S -BDTPA are around 150° and 30°, respectively, leading to the predicted g values of about ±2.7 × 10 –3 , which are very close to the experimental values (Table S8). Therefore, we present the mechanism of the chiral TADF based on chiral and achiral ICT as shown in the Jablonsky diagram (Figure c).…”

Section: Resultsmentioning

confidence: 99%

Solution-Processable Chiral Boron Complexes for Circularly Polarized Red Thermally Activated Delayed Fluorescent Devices

Xue

Wang

et al. 2021

ACS Appl. Mater. Interfaces

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Circularly polarized luminescence (CPL) molecules, especially those with thermally activated delayed fluorescence (TADF) properties, have attracted considerable attention due to their great potential for chiroptical organic light emitting diode (OLED) devices. Here we developed a new pair of TADF emitters with CPL based on boron complexes using chiral donor (cD) binaphthalene, acceptor (A) biphenyl boron β-diketonate, and donor (D) biphenylamine in a cD–A–D architecture. With this design, both efficient intramolecular charge transfer (ICT) and chiral ICT for high-performance CPL were established, leading to high dissymmetry factors (|g lum|) up to 2.2 × 10–3 in solution and significantly red-shifted emission around 600 nm for red TADF with a quantum yield over 15% in doped films. More impressively, with these chiral TADF emitters, solution-processed red circularly polarized OLEDs (CP-OLEDs) exhibit external quantum efficiencies (EQEs) up to 2.0% and efficient circularly polarized electroluminescence with dissymmetry factors of 2.6 × 10–3, which are among the best performances of the reported solution-processed orange-red and red TADF CP-OLEDs. These results illustrate the great success of the cD–A–D strategy in designing high-performance CPL TADF emitters with axially chiral boron complexes, providing important clues to understand efficient chiral transfer for large |g lum| values and high device performance of CP-OLEDs.

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“…MeIAc is characterized by its high-lying triplet energy level and structural rigidity, and was utilized as a donor unit in our previous work to construct two D-A type CP-TADF emitters with satisfactory performance in devices, i.e., EQEs up to 23.7 % and g EL s up to 2.4 × 10 À 3 . [8] In the current work, the sp 3 hybridized carbon atom not only serves as a stable stereocenter to induce CPL properties, but also locks the molecular geometry to guarantee high conformational stability. Additionally, the fluorenyl unit within MeIAc extends the π-conjugation of the MR-TADF skeleton, which may simultaneously benefit oscillator strength and horizontal anisotropic orientation in devices.…”

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confidence: 91%

Chiral Multi‐Resonance TADF Emitters Exhibiting Narrowband Circularly Polarized Electroluminescence with an EQE of 37.2 %

Yang

Miao

et al. 2022

Angewandte Chemie

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Highly efficient circularly polarized luminescence (CPL) emitters with narrowband emission remain a formidable challenge for circularly polarized OLEDs (CP‐OLEDs). Here, a promising strategy for developing chiral emitters concurrently featuring multi‐resonance thermally activated delayed fluorescence (MR‐TADF) and circularly polarized electroluminescence (CPEL) is demonstrated by the integration of molecular rigidity, central chirality and MR effect. A pair of chiral green emitters denoted as (R)‐BN‐MeIAc and (S)‐BN‐MeIAc is designed. Benefited by the rigid and quasi‐planar MR‐framework, the enantiomers not only display mirror‐image CPL spectra, but also exhibit TADF properties with a high photoluminescence quantum yield of 96 %, a narrow FWHM of 30 nm, and a high horizontal dipole orientation of 90 % in the doped film. Consequently, the enantiomer‐based CP‐OLEDs achieved excellent external quantum efficiencies of 37.2 % with very low efficiency roll‐off, representing the highest device efficiency of all the reported CP‐OLEDs.

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Integrating molecular rigidity and chirality into thermally activated delayed fluorescence emitters for highly efficient sky-blue and orange circularly polarized electroluminescence

Abstract: By integrating high molecular rigidity and stable chirality, two pairs of D*-A type circularly polarized thermally activated delayed fluorescence (CP-TADF) emitters with almost absolute quasi-equatorial conformer geometry and excellent photoluminescence...

Cited by 83 publications

References 82 publications

Deep‐Red Fluorescence from AIE‐Active Luminophore: High‐Brightness and Wide‐Range Piezochromism**

Deep‐Red Fluorescence from AIE‐Active Luminophore: High‐Brightness and Wide‐Range Piezochromism**

Solution-Processable Chiral Boron Complexes for Circularly Polarized Red Thermally Activated Delayed Fluorescent Devices

Chiral Multi‐Resonance TADF Emitters Exhibiting Narrowband Circularly Polarized Electroluminescence with an EQE of 37.2 %

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