Influence of Annealing Temperature on Weak-Cavity Top-Emission Red Quantum Dot Light Emitting Diode

Lee, Chun Yu; Kuo, Ya Pei; Chen, Peng Yu; Lu, Hsieh Hsing; Lin, Ming-Nan

doi:10.3390/nano9111639

Cited by 14 publications

(8 citation statements)

References 24 publications

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“…The efficiency of QD-based light-emitting diodes (QD-LEDs) has been improved steadily over the past two decades, and one of the most important breakthroughs was made by employing a metal oxide semiconductor in the electron transport layer (ETL). Suitable energy levels and high electron mobility of metal oxide semiconductors led to efficient charge injection and transport, thereby resulting in notable progress in the luminescence efficiency of QD-LEDs [17][18][19][20]. Various types of metal oxide semiconductors have been employed and investigated, and among those metal oxide semiconductors, 2 of 9 zinc oxide (ZnO) has been the most widely employed because of their easy processability, excellent electrical properties, and transparency [21,22].…”

Section: Introductionmentioning

confidence: 99%

Double Metal Oxide Electron Transport Layers for Colloidal Quantum Dot Light-Emitting Diodes

et al. 2020

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The performance of colloidal quantum dot light-emitting diodes (QD-LEDs) have been rapidly improved since metal oxide semiconductors were adopted for an electron transport layer (ETL). Among metal oxide semiconductors, zinc oxide (ZnO) has been the most generally employed for the ETL because of its excellent electron transport and injection properties. However, the ZnO ETL often yields charge imbalance in QD-LEDs, which results in undesirable device performance. Here, to address this issue, we introduce double metal oxide ETLs comprising ZnO and tin dioxide (SnO2) bilayer stacks. The employment of SnO2 for the second ETL significantly improves charge balance in the QD-LEDs by preventing spontaneous electron injection from the ZnO ETL and, as a result, we demonstrate 1.6 times higher luminescence efficiency in the QD-LEDs. This result suggests that the proposed double metal oxide ETLs can be a versatile platform for QD-based optoelectronic devices.

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Section: Introductionmentioning

confidence: 99%

Double Metal Oxide Electron Transport Layers for Colloidal Quantum Dot Light-Emitting Diodes

et al. 2020

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“…To better expose the weak emission signal, the vertical axis is set as a log scale. Interestingly, a wide side emission from 430 to 550 nm due to TFB 36,37 can be seen in the figure for the ink-jet-printed device with TFB annealed at 130 °C. This is hard evidence for the carriers leaked through the QD layer and recombined in the TFB layer.…”

Section: ■ Results and Discussionmentioning

confidence: 96%

Improved Ink-Jet-Printed CdSe Quantum Dot Light-Emitting Diodes with Minimized Hole Transport Layer Erosion

Tang

Jia

Ding

et al. 2021

ACS Appl. Electron. Mater.

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Ink-jet printing is a promising deposition technology, which is capable of large-area fabrication and mask-free patterning. For ink-jet-printed quantum dot (QD) light-emitting diodes (LEDs), the QDs are commonly dissolved in a mixture of solvent and thickener ink system. However, the hole transport layer could be eroded by this QD ink, leading to a rough surface morphology and resulting in the leakage of carriers and low device performance. This phenomenon was first and directly observed by using an atomic force microscope and a cross-sectional scanning electron microscope. We, therefore, redesigned the annealing process of the hole transport layer to achieve an optimized smooth surface with a reduced number of defects for ink-jet-printed QD LEDs (QLEDs). Optimized morphology brings back a maximum luminance of over 30,000 cd/m2 and an external quantum efficiency of 7.52% for the ink-jet-printed red QLEDs using CdSe QDs, which are comparable to those of the spin-coated device. Moreover, the operation lifetime of the ink-jet-printed device is also enhanced by the restored surface morphology. An enhanced T 50 lifetime of the ink-jet-printed device at 1000 cd/m2 is improved from 26 to 127 h, which converted to a long T 50 lifetime of 8013 h, when operated at 100 cd/m2.

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“…[ 21 ] According to the characterization of hole‐only and electron‐only devices, strong hole accumulation occurred near the Amp‐MSs compared to electron accumulation, which confirmed that the charge balance and mobility are influenced by the Amp‐MSs (Figure S5, Supporting Information). [ 22 ] The calculated trap‐filled limit voltage and trap density indicated that the Amp‐MSs can trap electrons and mobile holes. In addition, the formation of Amp‐MSs enhanced the light outcoupling owing to optical scattering.…”

Section: Resultsmentioning

confidence: 99%

Efficient Photon Extraction in Top‐Emission Organic Light‐Emitting Devices Based on Ampicillin Microstructures

et al. 2022

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The desire to enhance the efficiency of organic light‐emitting devices (OLEDs) has driven to the investigation of advanced materials with fascinating properties. In this work, the efficiency of top‐emission OLEDs (TEOLEDs) is enhanced by introducing ampicillin microstructures (Amp‐MSs) with dual phases (α‐/β‐phase) that induce photoluminescence (PL) and electroluminescence (EL). Moreover, Amp‐MSs can adjust the charge balance by Fermi level (EF) alignment, thereby decreasing the leakage current. The decrease in the wave‐guided modes can enhance the light outcoupling through optical scattering. The resulting TEOLED demonstrates a record‐high external quantum efficiency (EQE) (maximum: 68.7% and average: 63.4% at spectroradiometer; maximum: 44.8% and average: 42.6% at integrating sphere) with a wider color gamut (118%) owing to the redshift of the spectrum by J‐aggregation. Deconvolution of the EL intensities is performed to clarify the contribution of Amp‐MSs to the device EQE enhancement (optical scattering by Amp‐MSs: 17.0%, PL by radiative energy transfer: 9.1%, and EL by J‐aggregated excitons: 4.6%). The proposed TEOLED outperforms the existing frameworks in terms of device efficiency.

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Influence of Annealing Temperature on Weak-Cavity Top-Emission Red Quantum Dot Light Emitting Diode

Cited by 14 publications

References 24 publications

Double Metal Oxide Electron Transport Layers for Colloidal Quantum Dot Light-Emitting Diodes

Double Metal Oxide Electron Transport Layers for Colloidal Quantum Dot Light-Emitting Diodes

Improved Ink-Jet-Printed CdSe Quantum Dot Light-Emitting Diodes with Minimized Hole Transport Layer Erosion

Efficient Photon Extraction in Top‐Emission Organic Light‐Emitting Devices Based on Ampicillin Microstructures

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