Spiro derivatives as electron-blocking materials for highly stable OLEDs

Hu, Baohua; Ci, Zhenhua; Li, Liang; Li, Chong; Huang, Wei; Ichikawa, Musubu

doi:10.1016/j.orgel.2020.105879

Cited by 6 publications

(7 citation statements)

References 26 publications

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“…To systematically perform research on the proposed hypothesis for exciton decay and upconversion processes (Figure 1), we selected NaNaP-A as the TTU material based on the well-established characteristics for high TTU efficiency. [22,23] NaNaP-A has the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies of −6.0 and −3.0 eV, respectively. Here, we selected Tris-PCz as the hole-transport material, since Tris-PCz possesses the HOMO/LUMO levels of −5.6/−2.3 eV, indicating the possibility of exciplex formation between Tris-PCz and NaNaP-A.…”

Section: Resultsmentioning

confidence: 99%

An Overlooked Charge‐Transfer Interaction in the Interfacial Triplet–Triplet Upconversion Process in Blue Organic Light‐Emitting Diodes

Nguyen

Nakanotani

Adachi

2022

Advanced Optical Materials

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collide, alongside the formation of singlets and quintets, highly reactive "hot" triplets (>5 eV) would unwarrantedly be formed, leading to the rapid degradation of OLEDs. [5] Therefore, the control of overcrowded high-energy triplets has been the most critical issue for OLED research over the last 20 years. [4,[6][7][8] An alternative triplet-excitonic pathway in blue OLEDs is a triplet-triplet upconversion (TTU), which is a well-established solution for practical applications. [9,10] Anthracene derivatives that are a wellknown TTU material for blue OLEDs have the lowest-excited triplet energy level (T 1 ) of around 1.6 eV that is close to half of the singlet excited energy. The collision of the two low-energy triplets produces just enough energy for a singlet generation rather than the formation of a hot triplet that partially decays nonradiatively via a dissociation potential curve. For this reason, blue TTU-OLEDs provide a practical solution. Although the IQE in TTU-OLEDs falls short of 100%, TTU-OLEDs can theoretically gain the high singlet exciton production yield up to 62.5%.Despite the practical use of pure-blue TTU-OLEDs, TTU's underlying mechanism still remains debated with varied viewpoints. First, from the aspect of the exciton formation process, Monkman's group proposed a family of anthracene derivatives featuring high triplet levels (T n ) exceedingly twice the T 1 levels, leading to nearly 62.5% of IQE in OLEDs in 2013. [11,12] Recently, our group has proposed that spin-orbit coupling induced by intramolecular charge-transfer (CT) interaction in anthracene derivatives could facilitate TTU events. [13] Second, from the aspect of device engineering, in 2015, Xiang et al. revealed that the carrier recombination zone in a blue TTU-OLED exists in the emitter layer (EML) close to the interface between the EML and the hole-transport layer (HTL), [14] indicating the benefit from a dense triplet accumulation at the interface. Alternatively, an origin of the sub-bandgap EL in rubrene-based OLEDs was explained as the CT-sensitized TTU generating at the rubrene/ fullerene interface. [14,15] Further, B.-Y. Lin et al. proposed the CT-sensitized blue TTU-OLEDs to reduce a driving voltage. [16] Although the IQE from these CT-sensitized TTU-OLEDs was far from the theoretical limit, it has been suggested that the CT interface can facilitate TTU events at the interface according to the dense triplet accumulation. [14,[16][17][18][19] However, the interfacial CT formation has been claimed as the main reason for Two low-energy triplets can generate one singlet via triplet-triplet upconversion (TTU), and result in an exciton production yield exceeding 25% in conventional fluorescence-based organic light-emitting diodes (OLEDs). In most cases, since such low-energy triplets induce no serious OLED degradation, TTU-OLEDs are the only commercialized blue OLEDs so far. Herein, it is clarified that the charge-transfer (CT) interaction at a hole-transport/ emitter-layer interface is an overlooked pathway to enhance TTU yield s...

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Section: Resultsmentioning

confidence: 99%

An Overlooked Charge‐Transfer Interaction in the Interfacial Triplet–Triplet Upconversion Process in Blue Organic Light‐Emitting Diodes

Nguyen

Nakanotani

Adachi

2022

Advanced Optical Materials

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“…Xu et al successfully developed multicomponent reaction promoted by a chiral organocatalyst (Cat.3) for oxindole scaffolds (27), which includes a 1,3-hydrogen shift and a [3 + 2]cycloaddition reaction. These newly developed oxindoles have four consecutive stereogenic centers (Scheme 22).…”

Section: Cycloaddition Reactions For Spiro Derivativesmentioning

confidence: 99%

“…[11] Enantioenriched spiro derivatives [12] are characterized by the interesting fusion of two molecular rings linked by a common tetrasubstituted stereogenic center. They are an important component of several natural products, [13][14][15] bioactive compounds, [16][17][18][19][20] and find applications in asymmetric catalysis, [21][22][23][24] thermally stable OLED, [25][26][27][28][29][30][31] sensing, [32][33][34][35][36] and HMT (hole-transporting material). [37][38][39][40][41][42][43][44][45][46] Compared with singly condensed heterocycles spiro-hetero/carbocycles have the obvious advantage of structural compactness, which reduces lipophilicity.…”

Section: Introductionmentioning

confidence: 99%

Catalytic Stereoselective Multicomponent Reactions for the Synthesis of Spiro Derivatives: Recent Progress

Patel

2022

Eur J Org Chem

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Spiro derivatives are important scaffolding substances found in many natural products and pharmaceuticals. In the last decade, numerous new approaches based on multicomponent reactions have been explored for the selective and efficient development of new spiro derivatives using various organocatalytic and transition metal‐based catalytic systems. This Review discusses pioneering advances in the field of catalytic stereoselective multicomponent reactions for the preparation of various spiro derivatives. These include stereoselective Michael cascade cyclization reactions, cycloadditions, diastereoselective reactions, and miscellaneous reactions for the synthesis of spiro‐hetero/carbocycles. Advances in the last decade have made it possible to synthesize various spiro compounds with good to excellent stereoselectivity under appropriate reaction conditions. However, achieving high regioselectivity in several described multicomponent reactions remains a challenge. Organocatalysts and transition‐metal‐based catalysts play a crucial role in achieving this milestone. Proposed catalytic mechanisms and supporting evidence are highlighted in this Review. The progress described in catalytic stereoselective approaches for spiro derivatives is immense. However, it is expected that new stereoselective synthetic methods will soon be developed that can be widely used for the preparation of spiro‐heterocycles/carbocycles.

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“…12 [90][91][92]. Examples of charge blocking materials are BCP 2,9-dimethyl-5,7-diphenyl-1,10 phenanthroline (as an HBL), Alq 3 as an electron blocking layer, etc.…”

Section: Electron Blocking Layer (Ebl) and Hole Blocking Layer (Hbl)mentioning

confidence: 99%

Recent advances in efficient emissive materials-based OLED applications: a review

2021

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In the present time, organic light-emitting diode (OLED) is a very promising participant over light-emitting diodes (LEDs), liquid crystal display (LCD), and also another solid-state lighting device due to its low cost, ease of fabrication, brightness, speed, wide viewing angle, low power consumption, and high contrast ratio. The most prominent layer of OLED is the emissive layer because the device emission color, contrast ratio, and external efficiency depend of this layer's materials. This review ruminates on the basics of OLEDs, different light emission mechanisms, OLEDs achievements, and different types of challenges revealed in the field of OLEDs. This review's primary intention is to broadly discuss the synthesizing methods, physicochemical properties of conducting polymer polymethyl methacrylate (PMMA), and its polymeric nanocompositebased emissive layer materials for OLEDs application. It also discusses the most extensively used OLED fabrication techniques. PMMA-based polymeric nanocomposites revealed good transparency properties, good thermal stability, and high electrical conductivity, making suitable materials as an emissive layer for OLED applications.

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Spiro derivatives as electron-blocking materials for highly stable OLEDs

Cited by 6 publications

References 26 publications

An Overlooked Charge‐Transfer Interaction in the Interfacial Triplet–Triplet Upconversion Process in Blue Organic Light‐Emitting Diodes

An Overlooked Charge‐Transfer Interaction in the Interfacial Triplet–Triplet Upconversion Process in Blue Organic Light‐Emitting Diodes

Catalytic Stereoselective Multicomponent Reactions for the Synthesis of Spiro Derivatives: Recent Progress

Recent advances in efficient emissive materials-based OLED applications: a review

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