A step by step strategy for solution-processed quantum dots light emitting diodes

2011 ◽  
Vol 1286 ◽  
Author(s):  
Hélène Bourvon ◽  
Stéphanie Le Calvez ◽  
David Vaufrey ◽  
Sylvia Meunier Della Gatta
Keyword(s):  
Quantum Dots ◽  
Ethylene Glycol ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Deposition Process ◽  
Production Costs ◽  
Layer By Layer ◽  
Anisotropic Conductivity ◽  
Light Emitting ◽  
Hybrid Devices

ABSTRACTSolution-based printing and coating processes have the potential to dramatically reduce the production costs of Organic Light Emitting Diodes. This is particularly true for Quantum Dots Light Emitting Diode (QDLEDs), the newborn in the field of LEDs, due to quantum dots price prohibiting wastage. Here, we report our latest results on the development of solutionprocessed QDLEDs. We have implemented a layer by layer strategy, from a whole evaporated small molecule based OLED to a hybrid QDLED developed by wet deposition techniques for the first layers and by evaporation for the last ones. Intermediate steps are discussed in this paper.First, we have worked on a poly(3,4-ethylenedioxythiophene poly(styrenesulfonate) (PEDOT:PSS) layer. The PEDOT:PSS formulation for inkjet printing and spin coating were optimised: wettability on an ITO substrate, jettability of the inkjet formulation and baking conditions were studied. Additives as surfactant and ethylene glycol were added to the commercial inkjet grade solution to improve the deposition process. As a consequence to this study, anisotropic conductivity of PEDOT:PSS was observed and is reported here. In particular, ethylene glycol demonstrated a strong ability to increase the parallel conductivity by several orders of magnitude, but not the vertical one.Then, inkjet-printed and spin-coated device performances are compared to complete this first study. Hybrid devices with an efficacy of 12cd/A at 4V were obtained, with 2.17 % of EQE, and a luminance of 4000 cd/m2 at 4V.Finally, we succeeded in the development of our first QDLED based on CdSe core/ CdSZnS shell quantum dots emitting at a wavelength of 600nm. Quantum dots were inkjet printed, in order to waste as little as possible this very expensive material.

All-solution processed inverted green quantum dot light-emitting diodes with concurrent high efficiency and long lifetime

2019 ◽  
Vol 6 (10) ◽  
pp. 2009-2015 ◽  
Author(s):  
Zhiwen Yang ◽  
Qianqian Wu ◽  
Gongli Lin ◽  
Xiaochuan Zhou ◽  
Weijie Wu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Shell Growth ◽  
Solution Processed ◽  
Light Emitting ◽  
Long Lifetime

An all-solution processed inverted green quantum dot-based light-emitting diode with concurrent high efficiency and long lifetime is obtained by precisely controlled double shell growth of quantum dots.

scholarly journals 23% power conversion efficiency light-emitting diodes using monolayer quantum dots

2021 ◽  
Author(s):  
Fengjia Fan ◽  
Yan Gao ◽  
Xiaonan Liu ◽  
Bo Li ◽  
Huaibin Shen ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Bias Voltage ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Power Conversion ◽  
Hole Transport ◽  
Light Emitting ◽  
Large Size ◽  
Recombination Current ◽  
Conversion Efficiencies

Abstract Ever since the first proposal of using colloidal quantum dots (QDs) as the active emitting layer of light-emitting diode (LED), a monolayer of QD is considered as a better option than the multilayer ones. Owing to the slow charge transport rate among different QD layers, quantum dot light-emitting diodes (QLEDs) adopting multilayer QDs need to be driven at higher than the bandgap bias voltage to achieve practically useful brightness, resulting in increased power consumptions and heat generations, and reduced device lifetimes. Unfortunately, QLEDs using monolayer QDs always suffer from unwanted recombination in hole transport layers (HTLs) and low external quantum efficiencies (EQEs) as a result of electron overflow from QDs into HTLs. Herein, we tackle this dilemma by packing QDs with large size into monolayers, which enables us to mitigate the unwanted electron overflow and retain high EQE. More importantly, it further allows us to boost the irradiative recombination current at bandgap voltage. By virtue of simultaneously obtained high EQE and irradiative recombination rate, we can achieve brightness of 1,100 cd m-2 and 3,000 cd m-2 at 100% and 105% bandgap voltages with record high power conversion efficiencies (PCEs) of 23% and 22%, respectively. Since heat generation has been depressed and devices can be operated at reduced bias voltage, they show unprecedented T95 operation lifetimes (the time for the luminance to decrease to 95% of the initial value) of more than 4,000 h with an initial brightness of 3,000 cd m-2, and equivalent T95 lifetimes of more than 20,000 h at 1,000 cd m-2.

scholarly journals Dual-functional quantum-dots light emitting diodes based on solution processable vanadium oxide hole injection layer

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tae Yeon Kim ◽  
Sungho Park ◽  
Byung Jun Kim ◽  
Su Been Heo ◽  
Jong Hun Yu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Vanadium Oxide ◽  
Reverse Bias ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Hole Injection ◽  
Light Emitting ◽  
Hole Injection Layer ◽  
Dual Functional ◽  
Solution Processable

AbstractDual-functional quantum-dots light emitting diodes (QLEDs) have been fabricated using solution processable vanadium oxide (V2O5) hole injection layer to control the carrier transport behavior. The device shows selectable functionalities of photo-detecting and light-emitting behaviors according to the different operating voltage conditions. The device emitted a bright green light at the wavelength of 536 nm, and with the maximum luminance of 31,668 cd/m2 in a forward bias of 8.6 V. Meanwhile, the device could operate as a photodetector in a reverse bias condition. The device was perfectly turned off in a reverse bias, while an increase of photocurrent was observed during the illumination of 520 nm wavelength light on the device. The interfacial electronic structure of the device prepared with different concentration V2O5 solution was measured in detail using x-ray and ultraviolet photoelectron spectroscopy. Both the highest occupied molecular orbital and the gap state levels were moved closer to the Fermi level, according to increase the concentration of V2O5 solution. The change of gap state position enables to fabricate a dual-functional QLEDs. Therefore, the device could operate both as a photodetector and as a light-emitting diode with different applied bias. The result suggests that QLEDs can be used as a photosensor and as a light-emitting diode for the future display industry.

scholarly journals A simple method to improve the performance of perovskite light-emitting diodes via layer-by-layer spin-coating CsPbBr3 quantum dots

RSC Advances ◽  
2018 ◽  
Vol 8 (48) ◽  
pp. 27201-27206
Author(s):  
Bobo Li ◽  
Xiaomeng Li ◽  
Xia Li ◽  
Haolin Liu ◽  
Zhaonan Li ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Spin Coating ◽  
Light Emitting Diodes ◽  
Layer By Layer ◽  
Schematic Diagram ◽  
Simple Method ◽  
Light Emitting ◽  
Cspbbr3 Quantum Dots

Schematic diagram of perovskite LEDs and EQE–voltage curves of these devices.

Patterned mist deposition of tri-colour CdSe/ZnS quantum dot films toward RGB LED devices

2012 ◽  
Vol 20 (2) ◽  
Author(s):  
S. Pickering ◽  
A. Kshirsagar ◽  
J. Ruzyllo ◽  
J. Xu
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Precursor Solution ◽  
Colloidal Quantum Dots ◽  
Colloidal Solutions ◽  
Light Emitting ◽  
Mist Deposition ◽  
Viable Method

AbstractIn this experiment a technique of mist deposition was explored as a way to form patterned ultra-thin-films of CdSe/ZnS core/shell nanocrystalline quantum dots using colloidal solutions. The objective of this study was to investigate the feasibility of mist deposition as a patterning method for creating multicolour quantum dot light emitting diodes. Mist deposition was used to create three rows of quantum dot light emitting diodes on a single device with each row having a separate colour. The colours chosen were red, green and yellow with corresponding peak wavelengths of 620 nm, 558 nm, and 587 nm. The results obtained from this experiment show that it is possible to create multicolour devices on a single substrate. The peak brightnesses obtained in this experiment for the red, green, and yellow were 508 cd/m, 507 cd/m, and 665 cd/m, respectively. The similar LED brightness is important in display technologies using colloidal quantum dots in a precursor solution to ensure one colour does not dominate the emitted spectrum. Results obtained in-terms of brightness were superior to those achieved with inkjet deposition. This study has shown that mist deposition is a viable method for patterned deposition applied to quantum dot light emitting diode display technologies.

Surface Organic Ligands-Passivated Quantum Dots: Toward High-Performance Light-Emitting Diodes with Long Lifetime

2021 ◽  
Author(s):  
Lishuang Wang ◽  
Ying Lv ◽  
Jie Lin ◽  
Jialong Zhao ◽  
Xingyuan Liu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
High Performance ◽  
Light Emitting Diodes ◽  
Organic Ligands ◽  
Colloidal Quantum Dots ◽  
Core Shell ◽  
Light Emitting ◽  
Long Lifetime

For quantum dots light-emitting diodes (QLEDs), typical colloidal quantum dots (QDs) are usually composed of a core/shell heterostructure which is covered with organic ligands as surface passivated materials to confine...

scholarly journals Unravelling the electron injection/transport mechanism in organic light-emitting diodes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tsubasa Sasaki ◽  
Munehiro Hasegawa ◽  
Kaito Inagaki ◽  
Hirokazu Ito ◽  
Kazuma Suzuki ◽  
...  
Keyword(s):  
Work Function ◽  
Transport Mechanism ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Electron Injection ◽  
Organic Light Emitting Diodes ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Organic Light ◽  
Materials Used

AbstractAlthough significant progress has been made in the development of light-emitting materials for organic light-emitting diodes along with the elucidation of emission mechanisms, the electron injection/transport mechanism remains unclear, and the materials used for electron injection/transport have been basically unchanged for more than 20 years. Here, we unravelled the electron injection/transport mechanism by tuning the work function near the cathode to about 2.0 eV using a superbase. This extremely low-work function cathode allows direct electron injection into various materials, and it was found that organic materials can transport electrons independently of their molecular structure. On the basis of these findings, we have realised a simply structured blue organic light-emitting diode with an operational lifetime of more than 1,000,000 hours. Unravelling the electron injection/transport mechanism, as reported in this paper, not only greatly increases the choice of materials to be used for devices, but also allows simple device structures.

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