Lifetime elongation of quantum-dot light-emitting diodes by inhibiting the degradation of hole transport layer

Lin, Bo‐Yen; Ding, Wenchen; Chen, Chia‐Hsun; Kuo, Ya-Pei; Lee, Jiun-Haw; Lee, Chun-Yu; Chiu, Tien‐Lung

doi:10.1039/d1ra03310g

Cited by 6 publications

(8 citation statements)

References 48 publications

(50 reference statements)

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“…Generally, QLED degradation can be caused by the HTL due to charge accumulation at the QD-HTL interface. [13][14][15] Also, the low lifetime of blue QLED is caused by the degradation of the QD-electron transport layer (ETL) interface. [16] But, the origin of InP-QLED degradation and the detailed experimental results are not shown in the literature.…”

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confidence: 99%

Understanding the Origin of Degradation of InP‐Quantum Dot Light‐Emitting Diodes

Shin

Lampande

Kim

et al. 2022

Adv Elect Materials

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The origin of degradation of InP‐QLED (quantum dot LED) is reported by comparing the stability of Cd‐QDs and organic Bebq2:Ir(mphmq)2(tmd) emissive layers (EMLs). The degradation causes of InP‐QLED are checked by measuring the stability of hole and electron only devices (HOD and EOD) against hole/electron, exciton stress, and hole/electron‐exciton stress conditions. The results show that the InP‐QDs layer is more vulnerable to exciton and electron‐exciton stress compared to the Cd‐QDs and Bebq2:Ir(mphmq)2(tmd) due to the increase of surface defects in the InP‐QDs after exciton and electron‐exciton stress, which increases non‐radiative Auger recombination process. However, InP‐QDs are relatively less stable against electron and hole stress than the Cd‐QDs and Bebq2:Ir(mphmq)2(tmd). To reduce the electron‐exciton stress on the InP‐QDs, an inverted red QLED with InP‐QDs:DBTA EML is fabricated. The QLED with InP‐QDs: hole transport layer (DBTA) shows a low driving voltage of 5.7 V, high external quantum efficiency (EQE) of 10.2%, and longer lifetime (T50:557 h at 1000 cd m−2) than the reference InP‐QDs device (T50: 29 h at 1000 cd m−2).

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confidence: 99%

Understanding the Origin of Degradation of InP‐Quantum Dot Light‐Emitting Diodes

Shin

Lampande

Kim

et al. 2022

Adv Elect Materials

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“…The VB-FNPD HODs show negligible changes in PL intensity after 48 h of electrical stress. In contrast, the TFB HODs show a significant decrease in PL intensity in the first 24 h of applied bias, which is similar to what Lin et al observed in the devices using TFB . The control devices showed no appreciable decrease in PL over the same period of time, which indicates that the loss is induced by hole current.…”

Section: Resultsmentioning

confidence: 99%

“…In order to further investigate the role of the HTL in the higher stability of the VB-FNPD QDLED, we study and compare changes in the PL of the QDs in the HODs over time without and with electrical stress, the latter under forward bias. As mentioned earlier, the general structure of the HODs is ITO/PEDOT:PSS/HTL/QD/NPB (20 nm)/MoO 3 (5 nm)/ 20 The control devices showed no appreciable decrease in PL over the same period of time, which indicates that the loss is induced by hole current. Since the excitation intensity was the same, the decrease in PL corresponds to a loss in the PLQY.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Stability Improvement in Quantum-Dot Light-Emitting Devices via a New Robust Hole Transport Layer

et al. 2022

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Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4′-(N-(4-butylphenyl))-diphenylamine)] (TFB) is commonly used as the organic hole transport layer (HTL) in high-efficiency Cd-based quantum-dot light-emitting devices (QDLEDs). Despite its good hole transport performance, limitations with its cross-linking properties often result in susceptibility to solvent damage when coating subsequent layers. Here, we investigate the use of a robust thermally cross-linked polymer, 9,9-bis[4-[(4-ethenylphenyl)methoxy]phenyl]-N2,N7-di-1-naphthalenyl-N2,N7-diphenyl-9H-fluorene-2,7-diamine (VB-FNPD), as an HTL for QDLEDs. The results show that using VB-FNPD instead of TFB can double the electroluminescence half-life (LT50) of the devices, leading to an LT50 of 10,100 h versus only 4900 h for the TFB device at an initial luminance (L 0) of 1000 cd m–2. Atomic force microscopy surface scans show that VB-FNPD HTLs have smoother and more uniform morphologies when compared to TFB, which may help improve the quality of the HTL/QD interface and QD film uniformity, both of which are important for long-lived QDLEDs. Steady-state photoluminescence studies on hole-only devices suggest that VB-FNPD is also more stable under hole current flow. Further investigations using capacitance versus voltage on the devices show that replacing TFB by VB-FNPD reduces charge accumulation in the devices, which is likely another factor in the stability improvement.

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“…[1,2]. Device efficiency for QLED is an important concern for real application, and thus various methods improving QLED performance had been reported, such as using electron blocking layer (EBL), stepwise hole transporting layer and positive aging for improving carrier balance in QLED [3,4,5].…”

Section: Introductionmentioning

confidence: 99%

P‐88: Efficiency Improvement of Top‐Emission Green Quantum‐Dot Light‐Emitting Diode with Dielectric‐Metal‐Dielectric Cathode

Lin

Chen

Lin

et al. 2022

Symp Digest of Tech Papers

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In this work, we have demonstrated a top‐emission green quantum dot light‐emitting diode (QLED) with dielectric‐metal‐dielectric (DMD) structure as transparent cathode, which consisted of ytterbium (Yb)‐doped molybdenum oxide (MoO3)/Yb:Ag/MoO3. The DMD‐QLED exhibited a reduced operational voltage and higher efficiency by 1.43‐folds enhancement in external quantum efficiency relative to reference QLED due to the improvement of electron injection and transport as well as less exciton quenching.

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Lifetime elongation of quantum-dot light-emitting diodes by inhibiting the degradation of hole transport layer

Abstract: Developing a colloidal quantum-dot light-emitting device (QDLED) with an enhancement on efficiency and reliability by inhibiting HTL degradation.

Cited by 6 publications

References 48 publications

Understanding the Origin of Degradation of InP‐Quantum Dot Light‐Emitting Diodes

Understanding the Origin of Degradation of InP‐Quantum Dot Light‐Emitting Diodes

Stability Improvement in Quantum-Dot Light-Emitting Devices via a New Robust Hole Transport Layer

P‐88: Efficiency Improvement of Top‐Emission Green Quantum‐Dot Light‐Emitting Diode with Dielectric‐Metal‐Dielectric Cathode

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