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.

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.

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.

scholarly journals Effects of the Thickness of N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine on the Electro-Optical Characteristics of Organic Light-Emitting Diodes

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 966
Author(s):  
Sang-Geon Park ◽  
Won Jae Lee ◽  
Min Jong Song ◽  
Johngeon Shin ◽  
Tae Wan Kim
Keyword(s):  
Current Efficiency ◽  
Current Density ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Hole Transport ◽  
Organic Light Emitting Diodes ◽  
Optical Characteristics ◽  
Driving Voltage ◽  
Light Emitting ◽  
Organic Light

We examined the electro-optical characteristics of organic light emitting diodes according to the N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (TPD) thicknesses. The thicknesses of TPD were varied from 5 nm to 50 nm. The current density of the device with a TPD thickness of 5 nm was 8.94 times higher than that with a thickness of 50 nm at a driving voltage of 10 V. According to the conduction–current characteristics of conductors, the current densities improved with a decreasing TPD thickness. Different from the current density–voltage characteristics, the current efficiency–current density characteristics showed an improved efficiency with a 50 nm TPD thickness. The current efficiencies of a device with a 5 nm TPD thickness at a driving voltage of 10 V was 0.148 and at a 50 nm TPD thickness 0.993 cd/A, which was 6.7 times higher than the 5 nm TPD thickness. These results indicated that hole transport in Organic Light-Emitting Diode (OLED) devices were more efficient with thin 5 nm TPD than with thick 50 nm TPD, while electron transport was more efficient with thick 50 nm TPD, which caused conflicting results in the current efficiency-current density and current density-voltage characteristics according to TPD thicknesses.

Enhancing the Brightness of CsPbBr3 Quantum Dots Electroluminescence Light-Emitting Diodes through the Manipulation of PEDOT:PSS Films

2021 ◽  
Author(s):  
zhen Wang ◽  
Yue Peng ◽  
wei Wei Chen ◽  
sheng Yong Lu ◽  
sheng Xiao Tang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Low Temperature ◽  
Energy Level ◽  
Light Emitting Diodes ◽  
Hole Transport ◽  
Light Emitting ◽  
Styrene Sulfonate ◽  
Poly Styrene Sulfonate ◽  
Cspbbr3 Quantum Dots ◽  
Proper Energy

With solution-processability, low-temperature proper energy level and superior stability, Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is one common hole-transport material for the quantum dots light-emitting diodes (QLED) application. However, the conductivity of the...

A seed-mediated and double shell strategy to realize large-size ZnSe/ZnS/ZnS quantum dots for high color purity blue light-emitting diodes

Nanoscale ◽  
2021 ◽  
Author(s):  
Zhiwen Yang ◽  
Qianqian Wu ◽  
Xiaochuan Zhou ◽  
Fan Cao ◽  
Xuyong Yang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Light Emitting Diode ◽  
Electroluminescence Spectrum ◽  
Color Purity ◽  
Half Maximum ◽  
Light Emitting ◽  
Large Size ◽  
Seed Mediated ◽  
High Color Purity

Blue ZnSe/ZnS/ZnS quantum dots were prepared using a seed-mediated and double shell strategy, and the quantum dot-based light-emitting diode with electroluminescence spectrum peaked at 446 nm and full widths at half-maximum of 16 nm was fabricated.

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.

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