Difluoroboron-Enabled Thermally Activated Delayed Fluorescence

Li, Guijie; Lou, Weiwei; Wang, Dan; Deng, Chao; Zhang, Qisheng

doi:10.1021/acsami.9b08107

Cited by 59 publications

(33 citation statements)

References 70 publications

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“…In 2019, Li's group developed four green TADF materials (NOBF2-Cz, NOBF2-DTCz, NOBF2-DPCz, and NOBF2-DMAC) based on difluoroboron acceptors (Figure 11). [63] When increasing the electron-donating strength of donors, the HOMO energy level would decrease, causing the reduced energy gap and a green emission in NOBF2-DMAC (542 nm). The result indicates that the emission wavelength can be adjusted by introducing donors with different electron-donating ability.…”

Section: The Tadf Molecules With Green Emissionmentioning

confidence: 99%

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

Che

Xie

2020

Asian J Org Chem

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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.

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Section: The Tadf Molecules With Green Emissionmentioning

confidence: 99%

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

Che

Xie

2020

Asian J Org Chem

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“…However, the half-lifetime at a constant driving current density of 10 mA/cm 2 reached to 2,354 h. They demonstrated the first trial of design and synthesis of four-coordinate boron and tridentate dppy ligand-based blue TADF emitters. Later, Li G. et al (2019) reported a new series of tetracoordinated blue TADF emitters using donor-acceptor BF2-type skeleton. Tetracoordinated difluoroboron molecules are air-stable, and they can enhance the molecular rigidity to have a high PLQY.…”

Section: Partially Bridged Boron-type Acceptor For Blue Thermally Actmentioning

confidence: 99%

Recent Advancement in Boron-Based Efficient and Pure Blue Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Diodes

et al. 2020

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In the last few years, electron-deficient materials have been actively researched for application in organic light-emitting diode (OLED) as dopant and electron-transporting materials. The boron-containing materials are interesting as they give good emissive properties in solid state with an electron-accepting character. Recently, many boron-containing materials are used as emissive materials for thermally activated delayed fluorescence (TADF) OLED applications. In this review, boron acceptor-based push-pull small molecules used for application in blue TADF OLEDs are reviewed, covering their different types of acceptor, molecular design, structure-property relation, material properties, and device properties. Also, the importance of boron acceptors to address the key issue of blue TADF OLEDs is discussed.

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“…Almost simultaneously, another series of ESIPT‐blocked BF 2 complexes was reported as efficient and stable TADF emitters in OLEDs. [ 117 ] Despite their high PLQY values (65% to 99%), these compounds show moderate EQE values (11% to 15.8%) in the blue‐green region due to their comparatively large Δ E ST values (0.08 to 0.22 eV). Importantly, lifetime studies of NOBF 2 ‐DPCz‐ and NOBF 2 ‐DMAc‐doped OLEDs exhibited long operational lifetimes of 54 and 920 h at 50% of their initial luminescence at 500 cd m −2 , respectively.…”

Section: Four‐coordinate Boron‐based Tadf Emittersmentioning

confidence: 99%

Three‐ and Four‐Coordinate, Boron‐Based, Thermally Activated Delayed Fluorescent Emitters

Kothavale

Lee

2020

Advanced Optical Materials

136

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After the first report of organometallic complex-based phosphorescent emitting materials, [5] it was possible to realize 100% internal quantum efficiency in phosphorescent OLEDs (PhOLEDs). [6] Using strong spin-orbit coupling (SOC) of heavy metals such as platinum or iridium, it was possible to surpass the limit of spin statistics and utilize all triplet excitons as well as singlet excitons in PhOLEDs. [7-10] After a huge improvement in the external quantum efficiencies (EQEs) in PhOLEDs, it was possible to commercialize green and red PhOLEDs as replacements for green and red fluorescent OLEDs. However, blue fluorescent OLEDs could not be replaced with PhOLEDs due to lifetime issues. [11,12] Although the currently commercialized OLEDs are mainly based on PhOLEDs, serious issues such as high cost, need for rare materials, and environmental sustainability of the phosphorescent emitters used have forced researchers to identify an alternative to PhOLEDs. [13,14] Recently, TADF OLEDs have emerged as a viable alternative to PhOLEDs due to their capability to exhibit 100% internal quantum efficiency (like PhOLEDs) by harvesting both singlet and triplet excitons through a reverse intersystem crossing (RISC) mechanism. [15-19] As the emitters used in TADF OLEDs are purely organic materials, they are inexpensive, readily available, and offer a large number of design opportunities. They can be easily tuned for different colors and can also serve as efficient host materials in the emitting layers. After the first report of a high EQE TADF OLED in 2012, [20] a number of highly efficient blue, green, and red TADF OLEDs have been reported. [21-36] Although short device lifetime and poor color purity are the main obstacles in commercial application of TADF OLEDs, they are promising because they have obtained high EQEs equal to or higher than that of the PhOLEDs. Commercially applicable, highly efficient, stable, and pure color TADF emitters must have four important characteristics of small singlet-triplet energy gap (ΔE ST), high photoluminescence quantum yield (PLQY), small full width at half-maximum (FWHM), and stability of the emitting materials. However, it is difficult to achieve all four factors in a single molecular design. [17] For example, a small ΔE ST can be obtained through separation of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) using highly twisted molecular structures. However, a high PLQY will be realized by maximizing the overlap between the HOMO and LUMO. The two factors are contradictory, but they are necessary Recent developments in purely organic-material-based thermally activated delayed fluorescence (TADF) emitters are helping to make them suitable for commercial applications in the near future. In spite of their high external quantum efficiencies, the broad emission spectra and short device lifetimes are the main barriers to using TADF emitters. Among the classes of materials, boron-embedded polycyclic aromatic compounds have shown potential as TADF emitte...

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Difluoroboron-Enabled Thermally Activated Delayed Fluorescence

Cited by 59 publications

References 70 publications

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

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

Recent Advancement in Boron-Based Efficient and Pure Blue Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Diodes

Three‐ and Four‐Coordinate, Boron‐Based, Thermally Activated Delayed Fluorescent Emitters

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