Effect of anode buffer layer on the efficiency of inverted quantum-dot light-emitting diodes

Cho, Ye Ram; Kang, Pil-Gu; Shin, Dong Heon; Kim, Jihoon; Maeng, Min-Jae; Sakong, Jeonghun; Hong, Jong-Am; Park, Yongsup; Suh, Min Chul

doi:10.7567/apex.9.012103

Cited by 15 publications

(11 citation statements)

References 24 publications

(24 reference statements)

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“…If MoO 3 is completely replaced with HATCN (i.e., in D4), the leakage current increases such that the luminance and current efficiency decrease drastically, illustrating the poor charge injection capability of HATCN compared with MoO 3 when used alone as the charge injection material. 32,33 Therefore, it can be clearly seen that the improvements in device performances brought by the insertion of HATCN indeed mainly originate from its passivation effect on the underlying CBP layer. The passivation effect of HATCN is effective on not only CBP but also other organic hole transport layers that are vulnerable to thermal damages.…”

Section: Resultsmentioning

confidence: 99%

“…Nevertheless, D3 still exhibits considerably higher CE than D2 at high current injection, with an enhancement factor of 18% for the maximum CE. If MoO 3 is completely replaced with HATCN (i.e., in D4), the leakage current increases such that the luminance and current efficiency decrease drastically, illustrating the poor charge injection capability of HATCN compared with MoO 3 when used alone as the charge injection material. , Therefore, it can be clearly seen that the improvements in device performances brought by the insertion of HATCN indeed mainly originate from its passivation effect on the underlying CBP layer.…”

Section: Results and Discussionmentioning

confidence: 99%

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Efficiency Improvement of Quantum Dot Light-Emitting Diodes via Thermal Damage Suppression with HATCN

Liu

Dong

Wang

et al. 2021

ACS Appl. Mater. Interfaces

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With many advantages including superior color saturation and efficiency, quantum dot light-emitting diodes (QLEDs) are considered a promising candidate for the next-generation displays. Emission uniformity over the entire device area is a critical factor to the overall performance and reliability of QLEDs. In this work, we performed a thorough study on the origin of dark spots commonly observed in operating QLEDs and developed a strategy to eliminate these defects. Using advanced cross section fabrication and imaging techniques, we discovered the occurrence of voids in the organic hole transport layer and directly correlated them to the observed emission nonuniformity. Further investigations revealed that these voids are thermal damages induced during the subsequent thermal deposition of other functional layers and can act as leakage paths in the device. By inserting a thermo-tolerant 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HATCN) interlayer with an optimized thickness, the thermally induced dark spots can be completely suppressed, leading to a current efficiency increase by 18%. We further demonstrated that such a thermal passivation strategy can work universally for various types of organic layers with low thermal stability. Our findings here provide important guidance in enhancing the performances and reliability of QLEDs and also other sandwich-structured devices via the passivation of heat-sensitive layers.

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Section: Resultsmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Efficiency Improvement of Quantum Dot Light-Emitting Diodes via Thermal Damage Suppression with HATCN

Liu

Dong

Wang

et al. 2021

ACS Appl. Mater. Interfaces

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“…The mismatch in electron and hole injection efficiency inevitably leads to a charge imbalance within QDLEDs and an accumulation of holes in the HTL in the immediate vicinity of its interface with the QD layer, a phenomenon which is believed to be one of the main contributors to poor efficiency and degradation via nonradiative Auger recombination. The MoO 3 HIL is commonly used in organic and QDLEDs because of its very deep Fermi level, allowing for better hole injection into HTLs with deep HOMO energy levels such as CBP . In contrast, the CHTL devices allow for the utilization of a wider variety of alternate HILs including those with shallower energy levels, such as HATCN, which would otherwise be difficult to use in order to avoid a large hole injection barrier at the HTL/HIL interface.…”

Section: Results and Discussionmentioning

confidence: 99%

Significant Enhancement in Quantum Dot Light-Emitting Device Stability via a Cascading Hole Transport Layer

Davidson‐Hall

Aziz

2020

ACS Appl. Mater. Interfaces

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This work investigates the effect of the hole transport layer (HTL) on the stability of electroluminescent quantum dot light-emitting devices (QDLEDs). The electroluminescence half-life (LT50) of QDLEDs can be improved by 25× through the utilization of a cascading HTL (CHTL) structure with consecutive steps in the highest occupied molecular orbital energy level. Using this approach, a LT50 of 864,000 h (for an initial luminance of 100 cd m–2) is obtained for red QDLEDs using a conventional core/shell QD emitter. The CHTL primarily improves QDLED stability by shifting excessive hole accumulation away from the QD/HTL interface and toward the interlayer HTL/HTL interfaces. The wider electron–hole recombination zone in the CHTL for electrons that have leaked from the QD layer results in less HTL degradation at the QD/HTL interface. This work highlights the significant influence of the HTL on QDLED stability and represents the longest LT50 for a QDLED based on the conventional core/shell QD structure.

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“…Quantum dot light emitting diode (QLED) displays, as the most promising next-generation LED display, have attracted a lot of attention due to their stable optical performance, narrow spectral emission bandwidths, and high screen resolution. − As the emitting layer, the quantum dot (QD) film plays an important role in determining the performance of QLED devices. − Generally, the performance of the QD film depends on both the physicochemical property of QDs themselves and the quality of the assembled film, particularly the uniformity and the thickness. − A QD film with suitable thickness is always preferred for efficient charge transfer across the film . In particular, the surface roughness of the QD film affects both its charge-transport behavior and the charge balance with the neighboring layer in the multilayered device, which affects the quantum efficiency directly.…”

Section: Introductionmentioning

confidence: 99%

Ultrasmooth Quantum Dot Micropatterns by a Facile Controllable Liquid-Transfer Approach: Low-Cost Fabrication of High-Performance QLED

Zhang

Meng

et al. 2018

J. Am. Chem. Soc.

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Fabrication of a high quality quantum dot (QD) film is essentially important for a high-performance QD light emitting diode display (QLED) device. It is normally a high-cost and multiple-step solution-transfer process where large amounts of QDs were needed but with only limited usefulness. Thus, developing a simple, efficient, and low-cost approach to fabricate high-quality micropatterned QD film is urgently needed. Here, we proposed that the Chinese brush enables the controllable transfer of a QD solution directly onto a homogeneous and ultrasmooth micropatterned film in one step. It is proposed that the dynamic balance of QDs was enabled during the entire solution transfer process under the cooperative effect of Marangoni flow aroused by the asymmetric solvent evaporation and the Laplace pressure different by conical fibers. By this approach, QD nanoparticles were homogeneously transferred onto the desired area on the substrate. The as-prepared QLED devices show rather high performances with the current efficiencies of 72.38, 26.03, and 4.26 cd/A and external quantum efficiencies of 17.40, 18.96, and 6.20% for the green, red, and blue QLED devices, respectively. We envision that the result offers a low-cost, facile, and practically applicable solution-processing approach that works even in air for fabricating high-performance QLED devices.

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Effect of anode buffer layer on the efficiency of inverted quantum-dot light-emitting diodes

Cited by 15 publications

References 24 publications

Efficiency Improvement of Quantum Dot Light-Emitting Diodes via Thermal Damage Suppression with HATCN

Efficiency Improvement of Quantum Dot Light-Emitting Diodes via Thermal Damage Suppression with HATCN

Significant Enhancement in Quantum Dot Light-Emitting Device Stability via a Cascading Hole Transport Layer

Ultrasmooth Quantum Dot Micropatterns by a Facile Controllable Liquid-Transfer Approach: Low-Cost Fabrication of High-Performance QLED

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