Removal and passivation of surface defects in perforated GaN-based light-emitting diodes

2009 ◽  
Author(s):  
Y. Yang ◽  
X. A. Cao
Keyword(s):  
Light Emitting Diodes ◽  
Surface Defects ◽  
Light Emitting

scholarly journals Phenylalkylammonium passivation enables perovskite light emitting diodes with record high-radiance operational lifetime: the chain length matters

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yuwei Guo ◽  
Sofia Apergi ◽  
Nan Li ◽  
Mengyu Chen ◽  
Chunyang Yin ◽  
...  
Keyword(s):  
Chain Length ◽  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Light Emitting Diodes ◽  
Surface Defects ◽  
Theoretical Modelling ◽  
Ion Migration ◽  
Light Emitting ◽  
Operational Lifetime ◽  
Chain Lengths

AbstractPerovskite light emitting diodes suffer from poor operational stability, exhibiting a rapid decay of external quantum efficiency within minutes to hours after turn-on. To address this issue, we explore surface treatment of perovskite films with phenylalkylammonium iodide molecules of varying alkyl chain lengths. Combining experimental characterization and theoretical modelling, we show that these molecules stabilize the perovskite through suppression of iodide ion migration. The stabilization effect is enhanced with increasing chain length due to the stronger binding of the molecules with the perovskite surface, as well as the increased steric hindrance to reconfiguration for accommodating ion migration. The passivation also reduces the surface defects, resulting in a high radiance and delayed roll-off of external quantum efficiency. Using the optimized passivation molecule, phenylpropylammonium iodide, we achieve devices with an efficiency of 17.5%, a radiance of 1282.8 W sr−1 m−2 and a record T50 half-lifetime of 130 h under 100 mA cm−2.

Efficiency degradation induced by surface defects-assisted tunneling recombination in GaN/InGaN micro-light-emitting diodes

2021 ◽  
Vol 118 (2) ◽  
pp. 021105
Author(s):  
Jian Yin ◽  
Ehsanollah Fathi ◽  
Hossein Zamani Siboni ◽  
Chao Xu ◽  
Dayan Ban
Keyword(s):  
Light Emitting Diodes ◽  
Surface Defects ◽  
Light Emitting ◽  
Tunneling Recombination ◽  
Assisted Tunneling

Self-Activated Green-Yellow Emitting Gd2CaZnO5 Phosphor for Efficient Ultra-Violet Light-Emitting Diodes

2020 ◽  
Vol 20 (6) ◽  
pp. 3754-3761 ◽  
Author(s):  
Naina Lohia ◽  
Savvi Mishra ◽  
Swati Bishnoi ◽  
G. Swati ◽  
Vishnu V. Jaiswal ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Surface Defects ◽  
Broad Band ◽  
Ultra Violet ◽  
Yellow Emission ◽  
Electromagnetic Spectrum ◽  
Light Emitting ◽  
Ultra Violet Light ◽  
Violet Light ◽  
High Temperature Xrd

A new self-activated green-yellow emitting Gd2CaZnO5 (GCZO) phosphor was synthesized using solid-state reaction method at high-temperature. XRD analysis confirmed the orthorhombic structure of the sample with the Pbnm space group. SEM micrographs reveal the irregular morphology with micron sized particles. Detailed photoluminescence (PL) analysis revealed that the excitation of the phosphor lies in the UV range (˜377 nm) with the related broad green-yellow emission centered at 530 nm. The broad band emission ranging from ˜450 nm to 650 nm can be attributed to the surface defects and oxygen vacancies. The calculated luminescence decay lifetime for the optimized phosphor was found to be 2.925 μs. Furthermore, the color-coordinate (x, y) were calculated and found to be (0.44, 0.45), which lies in the green-yellow (˜540 nm) region of the electromagnetic spectrum. The values of color coordinates and Color correlated temperature of 3289 K support the synthesized phosphor for the emission of warm white-light. These results perfectly established the suitability of this green-yellow emitting GCZO phosphor for Ultra-Violet Light-Emitting Diodes (LEDs) excited white-LED applications.

Inkjet printed organic light-emitting diodes employing organometal-halide perovskite as hole transport layer

2021 ◽  
Author(s):  
Lei Liu ◽  
Dongyu Zhang ◽  
Tao Chu ◽  
Yihua Jian ◽  
fan yu ◽  
...  
Keyword(s):  
Inkjet Printing ◽  
Power Efficiency ◽  
Light Emitting Diodes ◽  
Surface Defects ◽  
Hole Transport ◽  
Transport Layer ◽  
Hole Injection ◽  
Hole Transport Layer ◽  
Light Emitting ◽  
Perovskite Materials

Abstract Due to their narrow spectrum and high photoluminescence quantum yield, organic-inorganic hybrid perovskite materials have become an important emitter for light-emitting diodes (LED). In addition to the perovskite emitters, other perovskite materials such as methyl lead ammonium chloride (MAPbCl3) with high charge mobility can potentially be used as excellent charge transport materials. In this work, phosphorescence LED devices in which MAPbCl3 was employed as hole transport layer (HTL) was designed and fabricated by inkjet printing process. Ethanolamine was added to the PEDOT:PSS hole injection layer (HIL) to control the crystallization process and to suppress the surface defects of MAPbCl3. In addition, polyethylene oxide was doped into MAPbCl3 to improve the printability and the quality of film formation. The "blurred interface" concept was successively applied to enable for the first time the inkjet printing of three layers (HIL, HTL and emitter layers) in the LEDs. The fabricated multilayer LEDs achieved the maximum external quantum efficiency of 8.9 %, maximum current efficiency of 30.8 cd/A, and maximum power efficiency of 10.7 lm/W. A 40*40 mm2 OLED light emitting device was successfully fabricated by inkjet printing technology.

scholarly journals Hard and soft Lewis-base behavior for efficient and stable CsPbBr3 perovskite light-emitting diodes

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Changjiu Sun ◽  
Junli Wei ◽  
Jian Zhao ◽  
Yuanzhi Jiang ◽  
Yilong Wang ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Surface Defects ◽  
Lewis Base ◽  
Defect States ◽  
Light Emitting ◽  
Lewis Bases ◽  
Molecule Design ◽  
Electron Withdrawing Group ◽  
Powerful Electron

Abstract All-inorganic CsPbBr3 perovskite is an attractive emission material for high-stability perovskite light-emitting diodes (PeLEDs), due to the high thermal and chemical stability. However, the external quantum efficiencies (EQEs) of CsPbBr3 based PeLEDs are still far behind their organic–inorganic congeners. Massive defect states on the surface of CsPbBr3 perovskite grains should be the main reason. Lewis base additives have been widely used to passivate surface defects. However, systematic investigations which relate to improving the passivation effect via rational molecule design are still lacking. Here, we demonstrate that the CsPbBr3 film’s optical and electrical properties can be significantly boosted by tailoring the hardness–softness of the Lewis base additives. Three carboxylate Lewis bases with different tail groups are selected to in-situ passivate CsPbBr3 perovskite films. Our research indicates that 4-(trifluoromethyl) benzoate acid anion (TBA−) with the powerful electron-withdrawing group trifluoromethyl and benzene ring possesses the softest COO− bonding head. TBA− thus acts as a soft Lewis base and possesses a robust combination with unsaturated lead atoms caused by halogen vacancies. Based on this, the all-inorganic CsPbBr3 PeLEDs with a maximum EQE up to 16.75% and a half-lifetime over 129 h at an initial brightness of 100 cd m−2 is thus delivered.

Injecting Inter-Layers and the Built-in Potential of Blue Polymer Light-Emitting Diodes

2000 ◽  
Vol 660 ◽  
Author(s):  
Thomas M. Brown ◽  
Ian S. Millard ◽  
David J. Lacey ◽  
Jeremy H. Burroughes ◽  
Richard H. Friend ◽  
...  
Keyword(s):  
Indium Tin Oxide ◽  
Light Emitting Diodes ◽  
Basic Structure ◽  
Thin Layers ◽  
Carrier Injection ◽  
Semiconducting Polymer ◽  
Light Emitting ◽  
Physical Mechanisms ◽  
Organic Solid ◽  
Polymer Light Emitting Diodes

ABSTRACTThe semiconducting-polymer/injecting-electrode heterojunction plays a crucial part in the operation of organic solid state devices. In polymer light-emitting diodes (LEDs), a common fundamental structure employed is Indium-Tin-Oxide/Polymer/Al. However, in order to fabricate efficient devices, alterations to this basic structure have to be carried out. The insertion of thin layers, between the electrodes and the emitting polymer, has been shown to greatly enhance LED performance, although the physical mechanisms underlying this effect remain unclear. Here, we use electro-absorption measurements of the built-in potential to monitor shifts in the barrier height at the electrode/polymer interface. We demonstrate that the main advantage brought about by inter-layers, such as poly(ethylenedioxythiophene)/poly(styrene sulphonic acid) (PEDOT:PSS) at the anode and Ca, LiF and CsF at the cathode, is a marked reduction of the barrier to carrier injection. The electro- absorption results also correlate with the electroluminescent characteristics of the LEDs.

Low-Temperature Operation of Green, Blue and UV InGaN/GaN Multiple-Quantum-Well Light-Emitting Diodes

2003 ◽  
Vol 764 ◽  
Author(s):  
X. A. Cao ◽  
S. F. LeBoeuf ◽  
J. L. Garrett ◽  
A. Ebong ◽  
L. B. Rowland ◽  
...  
Keyword(s):  
Quantum Well ◽  
Light Emitting Diodes ◽  
Multiple Quantum Well ◽  
Light Output ◽  
Localized States ◽  
Multiple Quantum ◽  
Nonradiative Recombination ◽  
Light Emitting ◽  
Temperature Range ◽  
Green Leds

Absract:Temperature-dependent electroluminescence (EL) of InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with peak emission energies ranging from 2.3 eV (green) to 3.3 eV (UV) has been studied over a wide temperature range (5-300 K). As the temperature is decreased from 300 K to 150 K, the EL intensity increases in all devices due to reduced nonradiative recombination and improved carrier confinement. However, LED operation at lower temperatures (150-5 K) is a strong function of In ratio in the active layer. For the green LEDs, emission intensity increases monotonically in the whole temperature range, while for the blue and UV LEDs, a remarkable decrease of the light output was observed, accompanied by a large redshift of the peak energy. The discrepancy can be attributed to various amounts of localization states caused by In composition fluctuation in the QW active regions. Based on a rate equation analysis, we find that the densities of the localized states in the green LEDs are more than two orders of magnitude higher than that in the UV LED. The large number of localized states in the green LEDs are crucial to maintain high-efficiency carrier capture at low temperatures.

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