scholarly journals Two-Dimensional Nanoplatelet Superlattices Overcoming Light Outcoupling Efficiency Limit in Perovskite Quantum Dot Light-Emitting Diodes

2021 ◽  
Author(s):  
Sudhir Kumar ◽  
Tommaso Marcato ◽  
Frank Krumeich ◽  
Yen-Ting Li ◽  
Yu-Cheng Chiu ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Self Assembly ◽  
Power Efficiency ◽  
Light Emitting Diodes ◽  
Transition Dipole Moment ◽  
Two Dimensional ◽  
Transition Dipole ◽  
Light Emitting ◽  
Planar Arrays ◽  
Out Of Plane

Abstract Quantum dot (QD) light-emitting diodes (LEDs) are emerging as one of the most promising candidates for next-generation displays. However, their intrinsic light outcoupling efficiency remains considerably lower than the organic counterpart, because it is not yet possible to control the transition-dipole-moment (TDM) orientation in QD solids at device level. Here, using the colloidal lead halide perovskite nanoplatelets (NPLs) as a model system, we report a directed self-assembly approach to form the two-dimensional superlattices (2DSLs) with the out-of-plane vector perpendicular to the substrate plane. The ligand and substrate engineering yields close-packed planar arrays with the side faces linked to each other. Emission polarization in individual NPLs rescales the radiation from horizontal and vertical transition dipoles, effectively resulting in preferentially horizontal TDM orientation. Based on the emissive thin films comprised of stacks of 2D superlattices, we demonstrate an enhanced ratio of horizontal dipole as revealed by 2D k-space spectroscopy. Our optimized single-junction QD LEDs showed peak external quantum efficiency of up to 24% and power efficiency exceeding 110 lm W-1, comparable to state-of-the-art organic LEDs.

scholarly journals ZnCuInS/ZnSe/ZnS Quantum Dot-Based Downconversion Light-Emitting Diodes and Their Thermal Effect

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Wenyan Liu ◽  
Yu Zhang ◽  
Cheng Ruan ◽  
Dan Wang ◽  
Tieqiang Zhang ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Power Efficiency ◽  
Light Emitting Diodes ◽  
Thermal Quenching ◽  
Cdse Qds ◽  
Light Emitting ◽  
Temperature Coefficients ◽  
Low Emission ◽  
Chromaticity Coordinates ◽  
Cie Chromaticity

The quantum dot-based light-emitting diodes (QD-LEDs) were fabricated using blue GaN chips and red-, yellow-, and green-emitting ZnCuInS/ZnSe/ZnS QDs. The power efficiencies were measured as 14.0 lm/W for red, 47.1 lm/W for yellow, and 62.4 lm/W for green LEDs at 2.6 V. The temperature effect of ZnCuInS/ZnSe/ZnS QDs on these LEDs was investigated using CIE chromaticity coordinates, spectral wavelength, full width at half maximum (FWHM), and power efficiency (PE). The thermal quenching induced by the increased surface temperature of the device was confirmed to be one of the important factors to decrease power efficiencies while the CIE chromaticity coordinates changed little due to the low emission temperature coefficients of 0.022, 0.050, and 0.068 nm/°C for red-, yellow-, and green-emitting ZnCuInS/ZnSe/ZnS QDs. These indicate that ZnCuInS/ZnSe/ZnS QDs are more suitable for downconversion LEDs compared to CdSe QDs.

scholarly journals Effects of UV Irradiation and Storage on the Performance of Inverted Red Quantum-Dot Light-Emitting Diodes

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1606
Author(s):  
Yu Luo ◽  
Junjie Wang ◽  
Pu Wang ◽  
Chaohuang Mai ◽  
Jian Wang ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Uv Irradiation ◽  
Power Efficiency ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Storage Period ◽  
Charge Balance ◽  
Light Emitting ◽  
Practical Applications ◽  
And Storage

We report the effects of ultraviolet (UV) irradiation and storage on the performance of ZnO-based inverted quantum-dot light-emitting diodes (QLEDs). The effects of UV irradiation on the electrical properties of ZnO nanoparticles (NPs) were investigated. We demonstrate that the charge balance was enhanced by improving the electron injection. The maximum external quantum efficiency (EQE) and power efficiency (PE) of QLEDs were increased by 26% and 143% after UV irradiation for 15 min. In addition, we investigated the storage stabilities of the inverted QLEDs. During the storage period, the electron current from ZnO gradually decreased, causing a reduction in the device current. However, the QLEDs demonstrated improvements in maximum EQE by 20.7% after two days of storage. Our analysis indicates that the suppression of exciton quenching at the interface of ZnO and quantum dots (QDs) during the storage period could result in the enhancement of EQE. This study provides a comprehension of the generally neglected factors, which could be conducive to the realization of high-efficiency and highly storage-stable practical applications.

Mechanisms of operation in quantum-dot light-emitting diodes

2019 ◽  
pp. 947
Author(s):  
Shoichi sano ◽  
Takashi Nagase ◽  
Takashi Kobayashi ◽  
Hiroyoshi Naito
Keyword(s):  
Quantum Dot ◽  
Light Emitting Diodes ◽  
Light Emitting

Enhanced Operational Stability of Quantum Dot based Light-Emitting Diodes by Improving Charge Injection Balance

2019 ◽  
pp. 886
Author(s):  
Seunghyun Rhee ◽  
Jun Hyuk Chang ◽  
Donghyo Hahm ◽  
Kyunghwan Kim ◽  
Hak June Lee ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Light Emitting Diodes ◽  
Charge Injection ◽  
Operational Stability ◽  
Light Emitting

scholarly journals On the degradation mechanisms of quantum-dot light-emitting diodes

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Song Chen ◽  
Weiran Cao ◽  
Taili Liu ◽  
Sai-Wing Tsang ◽  
Yixing Yang ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Light Emitting Diodes ◽  
Degradation Mechanisms ◽  
Light Emitting

Geometrically isomeric [Ir(iqbt)(ppy)(hpa)] complexes with differential molecule orientations for efficient near-infrared (NIR) polymer light-emitting diodes (PLEDs)

2021 ◽  
Vol 9 (36) ◽  
pp. 12068-12072
Author(s):  
Wentao Li ◽  
Jiaxiang Liu ◽  
Baowen Wang ◽  
Siyu Hou ◽  
Xingqiang Lü ◽  
...  
Keyword(s):  
Near Infrared ◽  
Light Emitting Diodes ◽  
Dipole Transition ◽  
Transition Dipole ◽  
Light Emitting ◽  
Horizontal Orientation ◽  
Polymer Light Emitting Diodes

Based on geometrical isomerisation of [Ir(C^N1)(C^N2)((N^O))]-tris-heteroleptic Ir(iii)-complexes, the augmented transition dipole transition (TMD) with a preferential horizontal orientation, which is beneficial for their NIR-phosphorescence, is reported.

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