Realizing 17.0% external quantum efficiency in red quantum dot light-emitting diodes by pursuing the ideal inkjet-printed film and interface

Xiong, Xueying; Wei, Changting; Xie, Liming; Chen, Ming; Tang, Pengyu; Shen, Wei; Deng, Zhengtao; Xia, Li; Duan, Yongjie; Su, Wenming; Zeng, Haibo; Cui, Zheng

doi:10.1016/j.orgel.2019.06.016

Cited by 45 publications

(38 citation statements)

References 53 publications

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“…So far, various QD patterning methods have been proposed, such as electro‐hydrodynamic jet printing, [ 11–14 ] transfer printing, [ 15–17 ] and inkjet printing. [ 18–26 ] Among these techniques, inkjet printing is highly advantageous for the implementation of full‐color QLED displays because of its fast processing time, comparatively straightforward quality that causes a minimal material usage by the drop‐on‐demand (DOD) process with high precision and accuracy, [ 18 ] and ability to be used in large‐area displays because it does not require an individual fine metal mask for RGB colors. Despite these advantages, the performance of inkjet‐printed devices is generally lower than that of spin‐coated devices.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, a number of researches focus on finding ways to improve the uniformity of inkjet‐printed films. [ 18–26 ] Moreover, the depositing morphologies of the inkjet droplets affect the efficiency, stability, and performance of the inkjet‐printed devices. In order to control this phenomenon, a widely used method in controlling the drying conditions of a droplet is employed using cosolvents, [ 11,19–26 ] mixing surfactants, [ 27–29 ] and/or fine‐tuning viscosity, [ 30–32 ] which optimized the Marangoni flow and capillary flow.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced Performance of Pixelated Quantum Dot Light‐Emitting Diodes by Inkjet Printing of Quantum Dot–Polymer Composites

Roh

Shin

et al. 2021

Advanced Optical Materials

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Inkjet printing of colloidal quantum dots (QDs) is considered a promising technology for application in full‐color quantum dot light‐emitting diode (QLED) displays. However, QLEDs that are inkjet printed in a pixel‐defining bank structure generally exhibit a low performance, mainly due to the nonuniformity in its QD morphology. In this study, an enhanced performance of inkjet‐printing‐based pixelated QLEDs is achieved by introducing small amounts of poly(methyl methacrylate) (PMMA) of different molecular weights into QD inks. When this QD–PMMA composite ink is adopted, uniform droplets are formed, originating from contact line depinning during drying. Inside the bank structure, the inkjet‐printed QD–PMMA composite film shows a smooth surface and little pileup at the bank edges. A pixelated QLED with PMMA with a molecular weight of 8 kDa exhibits the highest luminance of 73 360 cd m−2 and an external quantum efficiency of 2.8%, which are remarkably higher than that of the inkjet‐printed QLED subpixels without PMMA. The result is verified through the observation of the drying process and the QLED subpixel shapes under operation. Thus, inkjet‐printed QD–PMMA composite inks can be a promising strategy for future research on pixelated QLEDs for the fabrication process of full‐color QLED displays.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhanced Performance of Pixelated Quantum Dot Light‐Emitting Diodes by Inkjet Printing of Quantum Dot–Polymer Composites

Roh

Shin

et al. 2021

Advanced Optical Materials

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“…[ 23,25,26 ] For this issue, it has been reported that mixtures of low vapor pressure and high vapor pressure solvents like alkane solvent and phenyl‐cyclohexane (CHB) can suppress the coffee ring effect, which has been widely used in IJP ‐QLED. [ 14,17,26 ] A greater solvent evaporation flux can weaken the coffee ring effect to form a more uniform layer. [ 21,28 ] Therefore, the post‐treatment after IJP also plays a pivotal role in forming a uniform QD layer.…”

Section: Introductionmentioning

confidence: 99%

High Performance Inkjet‐Printed Quantum‐Dot Light‐Emitting Diodes with High Operational Stability

Jia

Tang

et al. 2021

Advanced Optical Materials

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Improving the stability of inkjet‐printed quantum dot light emitting diodes (QLEDs) is critical for the technology to become commercially viable. The major obstacle is the compromise between the printability of the ink system and the functionality of the carrier transport layers. Here, a ternary ink system consisting of octane, 1‐cyclohexyl‐ethanol, and n‐butyl acetate is reported, which solves the erosion between the printed quantum dot ink and the underneath hole transport layer. A gradient vacuum post‐treatment is developed to accompany the ternary ink system with gradient vacuum pressures, which is helpful in forming a uniform printing layer. Based on both technologies, the inkjet‐printed R/G/B QLEDS are fabricated with high resolution patterns, showing high efficiencies and stabilities. The external quantum efficiency of R/G/B devices is 19.3%, 18.0%, and 4.4%, respectively. Correspondingly, the half operating lifetime is up to 25 178 h @ 1000 cd m−2, 20 655 h @ 1000 cd m−2, and 46 h @ 100 cd m−2, respectively. The improvements in the ink engineering and post‐treatment in this study have taken the efficiency and stability of the devices to a higher level and confirm the application prospects of printed QLEDs in the display industry.

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“…Inkjet printing [ 11,12 ] is a mask‐free, material‐effective, and large‐area compatible manufacturing technology, and it has been considered to be appropriate for large‐scale production of QLED displays. [ 13–15 ] However, traditional inkjet printing only meets the demand of television display with pixel density of about 100 pixels per in. (PPI), rather than mobile phones which require high‐resolution pixels over 300 PPI.…”

Section: Introductionmentioning

confidence: 99%

High‐Resolution Pixelated Light Emitting Diodes Based on Electrohydrodynamic Printing and Coffee‐Ring‐Free Quantum Dot Film

Duan

Shao

et al. 2020

Adv Materials Technologies

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Inkjet printing for preparing quantum dot light emitting diodes (QLEDs) has become increasingly attractive due to its large‐area, low‐cost fabrication features. However, the rather low resolution and coarse morphology induced by the printing and uneven evaporation of droplet restrict its further development. Herein, electrohydrodynamic (EHD) printing and mixed solvent method are employed to fabricate high‐resolution pixelated QLEDs. By optimizing the mixed solvent ratio to weaken capillary flow, coffee‐ring‐free quantum dot (QD) films can be obtained. With the help of EHD printing process optimization and pixel defining layers introduction, high‐resolution pixelated QLED with 306 pixels per in. is achieved, which can meet the requirements of manufacturing mobile phones. Finally, an inverted pixelated QLED with a low turn‐on voltage of 3 V and a maximum luminance of 8533 cd m−2 is fabricated, demonstrating that the presented strategy has huge potential in high‐resolution and high‐quality QD display manufacturing.

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Realizing 17.0% external quantum efficiency in red quantum dot light-emitting diodes by pursuing the ideal inkjet-printed film and interface

Cited by 45 publications

References 53 publications

Enhanced Performance of Pixelated Quantum Dot Light‐Emitting Diodes by Inkjet Printing of Quantum Dot–Polymer Composites

Enhanced Performance of Pixelated Quantum Dot Light‐Emitting Diodes by Inkjet Printing of Quantum Dot–Polymer Composites

High Performance Inkjet‐Printed Quantum‐Dot Light‐Emitting Diodes with High Operational Stability

High‐Resolution Pixelated Light Emitting Diodes Based on Electrohydrodynamic Printing and Coffee‐Ring‐Free Quantum Dot Film

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