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.

Temperature Dependent Structural Evolution of Graphene Layers on 4H-SiC(0001)

2011 ◽  
Vol 679-680 ◽  
pp. 797-800 ◽  
Author(s):  
Sushant Sonde ◽  
Carmelo Vecchio ◽  
Filippo Giannazzo ◽  
Corrado Bongiorno ◽  
Salvatore di Franco ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Structural Evolution ◽  
Morphological Transformation ◽  
Temperature Dependent ◽  
Microscopy Imaging ◽  
Graphene Layers ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Mode Atomic Force Microscopy

In this study we examined the structural evolution of graphene grown on 8° off-axis 4H-SiC(0001) substrates at temperatures from 1600°C to 1700°C in Ar ambient. Morphological transformation of SiC substrate after annealing was examined by Tapping Mode Atomic Force Microscopy. Moreover, by etching-out graphene layers from graphitized SiC substrates in selective trenches we determined the number of graphene layers. Numbers of graphene layers were then independently confirmed by Transmission Electron Microscopy imaging.

REAL-TIME VISUALIZATION OF MORPHOLOGICAL EVOLUTION OF N, N'-di(naphthalene-1-yl)-N, N'-diphthalbenzidine THIN FILMS: VARIABLE TEMPERATURE ATOMIC FORCE MICROSCOPY STUDY

2002 ◽  
Vol 01 (05n06) ◽  
pp. 725-730 ◽  
Author(s):  
M. S. XU ◽  
J. B. XU ◽  
J. AN
Keyword(s):  
Thin Film ◽  
Atomic Force Microscopy ◽  
Morphological Evolution ◽  
Variable Temperature ◽  
Glassy State ◽  
Microscopy Study ◽  
Light Emitting ◽  
Force Microscopy ◽  
Atomic Force ◽  
Real Time Visualization

Variable temperature tapping mode atomic force microscopy is exploited to in situ visualize the morphological evolution of N, N'-di(naphthalene-1-yl)-N, N'-diphthalbenzidine (NPB) thin film. The apparent glass transition of the NPB thin film initially occurred at 60°C, proceeded until 95°C, and crystallization from the glassy state quickly appeared at 135°C. The NPB thin film gradually melted and disappeared when the temperature was above 175°C, revealing the underlying layer. These observations are technically helpful and significant to gauge the temperature dependent lifetime and luminance of organic light-emitting diodes.

Interface structure and formation between gold and trimethylcyclohexane polycarbonate

1999 ◽  
Vol 14 (9) ◽  
pp. 3538-3543 ◽  
Author(s):  
C. v. Bechtolsheim ◽  
V. Zaporojtchenko ◽  
F. Faupel
Keyword(s):  
Photoelectron Spectroscopy ◽  
Elevated Temperatures ◽  
Cluster Formation ◽  
Systematic Investigation ◽  
Temperature Dependent ◽  
Cross Sectional ◽  
Force Microscopy ◽  
Metal Diffusion ◽  
Atomic Force ◽  
Transmission Electron

This paper presents the results of a systematic investigation of structure and formation of the interface between gold and trimethylcyclohexane polycarbonate, particularly concerning interface evolvement during gold evaporation and the influence of evaporation rate, substrate temperature, and subsequent annealing. The means of investigation were cross-sectional transmission electron microscopy, atomic force microscopy, and x-ray photoelectron spectroscopy. Extensive metal diffusion into the polymer and cluster formation near the interface were observed at deposition rates of the order of one monolayer per minute and below. The penetration depth is strongly temperature dependent. At high evaporation rates metal aggregation at the surface prevents cluster formation inside the polymer. No diffusion into the polymer was observed from metal films deposited at room temperature after extensive annealing at elevated temperatures.

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.

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.

scholarly journals Slot-Die Coating of Double Polymer Layers for the Fabrication of Organic Light Emitting Diodes

Micromachines ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 53 ◽  
Author(s):  
Amruth C ◽  
Marco Colella ◽  
Jonathan Griffin ◽  
James Kingsley ◽  
Nicholas Scarratt ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Processing Parameters ◽  
Organic Light Emitting Diodes ◽  
Hole Injection ◽  
Light Emitting ◽  
Force Microscopy ◽  
Slot Die Coating ◽  
Atomic Force ◽  
Organic Light ◽  
Slot Die

This study presents the slot-die coating process of two layers of organic materials for the fabrication of organic light emitting diodes (OLEDs). Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), which is commonly used in OLEDs and in organic photovoltaic devices as the hole injection layer (HIL), has been deposited via slot-die coating. Uniform films of PEDOT:PSS were obtained after optimizing the slot-die processing parameters: substrate temperature, coating speed, and ink flow rate. The film quality was examined using optical microscopy, profilometry, and atomic force microscopy. Further, poly(9,9-dioctylfluorene) (F8) and poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT), a well know polymer blend F8:F8BT, which is used as an emissive layer in OLEDs, has been slot-die coated. The optoelectronic properties of the slot-die coated F8:F8BT films were examined by means of photoluminescence (PL) and electroluminescence (EL) studies. The fabricated OLEDs, consisting of slot-die coated PEDOT:PSS and F8:F8BT films, were characterized to record the brightness and current efficiency.

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.

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