Solution-Processed High-Efficiency Organic Phosphorescent Devices Utilizing a Blue Ir(III) Complex

2008 ◽  
Vol 8 (6) ◽  
pp. 2990-2995
Author(s):  
Eunsil Han ◽  
Yi-Yeol Lyu ◽  
Tae-Woo Lee ◽  
Younghun Byun ◽  
Ohyun Kwon ◽  
...  
Keyword(s):  
High Efficiency ◽  
Solution Process ◽  
Pmma Film ◽  
Device Performance ◽  
Light Emitting ◽  
Color Coordinates ◽  
Light Emitting Devices ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

We report high-efficiency blue phosphorescence organic light-emitting devices by solution process utilizing a blue Ir(III) complex [(F2ppy)2Ir(ph-imz)CN] (F2ppy = 2′,6′ -difluoro-2-phenyl pyridine and ph-imz = N-phenyl imidazole) blended with the host mCP (N, N′-dicarbazolyl-3,5-benzene), and the inert polymers polystyrene (PS) and polymethylmethacrylate (PMMA). The effects of the dopant confinement in the PS and PMMA matrix on the device performance are studied by field emission transmission electron microscopy (FE-TEM) and atomic force microscopy (AFM). The complex shows photoluminescence peaked at 458 nm with CIE color coordinates (0.14, 0.21) in solution and (0.14, 0.18) in doped PMMA film. The PS based device showed better device performance than the PMMA based device with a maximum luminous efficiency of (ηL) 5.11 cd/A with CIE color coordinates (0.17, 0.29) (at 10 mA/cm2) and a maximum luminance of 9765 cd/m2.

High Power 330 nm AlInGaN UV LEDs in the High Injection Regime

2003 ◽  
Vol 798 ◽  
Author(s):  
M. Gherasimova ◽  
J. Su ◽  
G. Cui ◽  
J. Han ◽  
H. Peng ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Threading Dislocation ◽  
Light Emitting ◽  
Force Microscopy ◽  
Sapphire Substrates ◽  
Atomic Force ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Dimensional Growth ◽  
Uv Leds

ABSTRACTWe report on the growth and testing of the light emitting diode structures incorporating quaternary AlInGaN active region with an emission wavelength of 330 nm. Small area circular devices were fabricated, yielding the output power of 110 μW measured with a bare-chip configuration in a high current injection regime (8 kA/cm2 for a 20 μm diameter device). Structural properties of the constituent epitaxial layers were evaluated by atomic force microscopy and transmission electron microscopy, resulting in the observation of two-dimensional growth morphologies of AlN and AlGaN, and the estimate of threading dislocation densities in the low 109 cm-2 range in the structures grown on sapphire substrates.

Organic light-emitting devices based on solution-processable small molecular emissive layers doped with interface-engineering additives

RSC Advances ◽  
2016 ◽  
Vol 6 (39) ◽  
pp. 33063-33071 ◽  
Author(s):  
Tae-Won Ha ◽  
Young-Baek Kim ◽  
Gi-Seok Heo ◽  
Inchan Hwang ◽  
Hong Goo Jeon ◽  
...  
Keyword(s):  
Solution Process ◽  
Simple Solution ◽  
Device Performance ◽  
Interface Engineering ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Organic Light ◽  
Solution Processable ◽  
Organic Light Emitting Devices

A simple solution-process to fabricate full-colour small molecular OLEDs is proposed. The incidence of nano-pinhole defects decreases sharply following the introduction of an interface-engineering additive, resulting in good device performance.

scholarly journals Thiocyanate-Treated Perovskite-Nanocrystal-Based Light-Emitting Diodes with Insight in Efficiency Roll-Off

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 367 ◽  
Author(s):  
Fang Chen ◽  
Karunakara Moorthy Boopathi ◽  
Muhammad Imran ◽  
Simone Lauciello ◽  
Marco Salerno
Keyword(s):  
High Stability ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Ammonium Thiocyanate ◽  
Conductive Atomic Force Microscopy ◽  
Light Emitting ◽  
Force Microscopy ◽  
Atomic Force ◽  
Thiocyanate Solution ◽  
Green Led

Light emitting diodes (LED) based on halide perovskite nanocrystals (NC) have received widespread attention in recent years. In particular, LEDs based on CsPbBr3 NCs were the object of special interest. Here, we report for the first time green LED based on CsPbBr3 NCs treated with ammonium thiocyanate solution before purification with polar solvent. The champion device fabricated based on the treated CsPbBr3 NCs showed high efficiency and high stability during operation as well as during storage. A study on morphology and current distribution of NC films under applied voltages was carried out by conductive atomic force microscopy, giving a hint on efficiency roll-off. The current work provides a facile way to treat sensitive perovskite NCs and to fabricate perovskite NC-based LED with high stability. Moreover, the results shed new light on the relation between film morphology and device performance and on the possible mechanism of efficiency roll-off in NC LED.

Dependence of the performance of light-emitting diodes on the molecular weight of the electroluminescent polymer PFO-MEH-PPV

2020 ◽  
Vol 98 (9) ◽  
pp. 575-581 ◽  
Author(s):  
Pierre-Louis M. Brunner ◽  
Dominic Laliberté ◽  
Minh Trung Dang ◽  
Guillaume Wantz ◽  
James D. Wuest
Keyword(s):  
Molecular Weight ◽  
Light Emitting Diodes ◽  
Gel Permeation Chromatography ◽  
Quantum Yields ◽  
Light Emitting ◽  
Force Microscopy ◽  
Active Layers ◽  
Atomic Force ◽  
Transmission Electron ◽  
Relative Quantum

Controlled synthesis of the electroluminescent polymer PFO-MEH-PPV (poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-co-(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene)]) provided samples of varying molecular weight (Mw) in the range 20–360 kDa, as determined by gel-permeation chromatography and light scattering. The samples were used as the active layers in organic light-emitting diodes (OLEDs), and the performance of the devices was examined as a function of Mw. Turn-on voltages fell in the range 1.92–2.78 V, luminances varied from 231 to 5826 cd/m2, and luminous efficacies ranged from 0.06 to 0.90 lm/W. The emitted colour was found to vary from green to yellow as Mw increases. Optimal performance was attained by using PFO-MEH-PPV with Mw = 100 kDa. To help reveal how Mw determines the performance of OLEDs, relative quantum yields of photoluminescence in solutions and films were measured, and films were characterized by atomic force microscopy and transmission electron microscopy.

Adhesion and Degradation of Organic and Hybrid Organic-Inorganic Light-Emitting Devices

2015 ◽  
Vol 1132 ◽  
pp. 185-203
Author(s):  
D.Y. Momodu ◽  
T. Tong ◽  
M.G. Zebaze Kana ◽  
W.O. Soboyejo
Keyword(s):  
Fracture Mechanics ◽  
Active Regions ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Force Microscopy ◽  
Future Design ◽  
Atomic Force ◽  
Interfacial Fracture Mechanics ◽  
Organic Light ◽  
Modeling And Experiments

This paper presents the results of a combined analytical, computational and experimental study of adhesion and degradation of Organic Light Emitting Devices (OLEDs). The adhesion between layers that are relevant to OLEDs is studied using force microscopy during Atomic Force Microscopy. The interfacial failure mechanisms associated with blister formation in OLEDs and the addition of TiO2nanoparticles (into active regions) are then elucidated using a combination of fracture mechanics/finite element modeling and experiments. The blisters observed in the models are shown to be consistent with the results from adhesion and interfacial fracture mechanics models. The implications of the work are discussed for the future design of OLED structures with improved lifetimes and robustness.

Hexagonal Pyramids Shaped GaN Light Emitting Diodes Array by N-polar Wet Etching

2013 ◽  
Vol 1538 ◽  
pp. 353-359
Author(s):  
Jun Ma ◽  
Liancheng Wang ◽  
Zhiqiang Liu ◽  
Guodong Yuan ◽  
Xiaoli Ji ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Active Regions ◽  
Wet Etching ◽  
Conductive Atomic Force Microscopy ◽  
Light Emitting ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Vertical Injection ◽  
Reduced Density

ABSTRACTIn this work, we investigated the influence of N-polar wet etching on the properties of nitride-based hexagonal pyramids array (HPA) vertical-injection light emitting diodes (V-LEDs). The cathodeluminescence images showed the randomly distribution of hexagonal pyramids with isolated active regions. The transmission electron microscopy images demonstrated the reduced density of threading dislocations. The IQE was estimated by temperature dependence of photoluminescence, which showed 30% increase for HPA V-LEDs compared with broad area (BA) V-LEDs. The improved extraction efficiency was verified by finite difference time domain simulation, which was 20% higher than that of roughened BA V-LEDs. The electrical properties of HPA V-LEDs were measured by conductive atomic force microscopy (CAFM) measurements. HPA V-LEDs exhibited much lower leakage current due to the improved crystal quality.

Temperature-dependent nanomorphology–performance relations in binary iridium complex blend films for organic light emitting diodes

2015 ◽  
Vol 17 (33) ◽  
pp. 21555-21563 ◽  
Author(s):  
Young-Tae Kim ◽  
Young-Hoon Kim ◽  
Jae-Bok Seol ◽  
Tae-Woo Lee ◽  
Chan-Gyung Park
Keyword(s):  
Morphological Evolution ◽  
Organic Light Emitting Diodes ◽  
Iridium Complex ◽  
Temperature Dependent ◽  
Binary Blend ◽  
Light Emitting ◽  
Blend Films ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

We described the morphological evolution occurring in PVK:Ir(ppy)3 binary blend films, with respect to thermal annealing up to 300 °C, by coupling atomic force microscopy and transmission electron microscopy.

Scanning tunneling microscopy and atomic force microscopy: New tools for biology

1989 ◽  
Vol 47 ◽  
pp. 778-779
Author(s):  
CE Bracker ◽  
P. K. Hansma
Keyword(s):  
Physical Property ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Small Scale ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
New Family ◽  
Small Probe ◽  
Atomic Force ◽  
Transmission Electron

A new family of scanning probe microscopes has emerged that is opening new horizons for investigating the fine structure of matter. The earliest and best known of these instruments is the scanning tunneling microscope (STM). First published in 1982, the STM earned the 1986 Nobel Prize in Physics for two of its inventors, G. Binnig and H. Rohrer. They shared the prize with E. Ruska for his work that had led to the development of the transmission electron microscope half a century earlier. It seems appropriate that the award embodied this particular blend of the old and the new because it demonstrated to the world a long overdue respect for the enormous contributions electron microscopy has made to the understanding of matter, and at the same time it signalled the dawn of a new age in microscopy. What we are seeing is a revolution in microscopy and a redefinition of the concept of a microscope.Several kinds of scanning probe microscopes now exist, and the number is increasing. What they share in common is a small probe that is scanned over the surface of a specimen and measures a physical property on a very small scale, at or near the surface. Scanning probes can measure temperature, magnetic fields, tunneling currents, voltage, force, and ion currents, among others.

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