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.

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.

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.

Exciplex-Forming Cohost for High Efficiency and High Stability Phosphorescent Organic Light-Emitting Diodes

2018 ◽  
Vol 10 (2) ◽  
pp. 2151-2157 ◽  
Author(s):  
Chun-Jen Shih ◽  
Chih-Chien Lee ◽  
Ying-Hao Chen ◽  
Sajal Biring ◽  
Gautham Kumar ◽  
...  
Keyword(s):  
High Stability ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Organic Light Emitting Diodes ◽  
Light Emitting ◽  
Organic Light

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.

Fault Isolation of MOL and FEOL Buried Defects Using Conductive Atomic Force Microscopy as a Complement to Passive Voltage Contrast Imaging

2017 ◽  
Author(s):  
Lucile C. Teague Sheridan ◽  
Linda Conohan ◽  
Chong Khiam Oh
Keyword(s):  
Atomic Force Microscopy ◽  
Cmos Technology ◽  
Fault Isolation ◽  
Contrast Imaging ◽  
Conductive Atomic Force Microscopy ◽  
Isolation Technique ◽  
Conductive Afm ◽  
Force Microscopy ◽  
Atomic Force ◽  
Voltage Contrast

Abstract Atomic force microscopy (AFM) methods have provided a wealth of knowledge into the topographic, electrical, mechanical, magnetic, and electrochemical properties of surfaces and materials at the micro- and nanoscale over the last several decades. More specifically, the application of conductive AFM (CAFM) techniques for failure analysis can provide a simultaneous view of the conductivity and topographic properties of the patterned features. As CMOS technology progresses to smaller and smaller devices, the benefits of CAFM techniques have become apparent [1-3]. Herein, we review several cases in which CAFM has been utilized as a fault-isolation technique to detect middle of line (MOL) and front end of line (FEOL) buried defects in 20nm technologies and beyond.

Fault Localization in Contact Level by Using Conductive Atomic Force Microscopy

2003 ◽  
Author(s):  
Jon C. Lee ◽  
J. H. Chuang
Keyword(s):  
Atomic Force Microscopy ◽  
Integrated Circuits ◽  
Fault Localization ◽  
Electrical Characterization ◽  
Conductive Atomic Force Microscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Optical Electron ◽  
Defect Isolation ◽  
Voltage Contrast

Abstract As integrated circuits (IC) have become more complicated with device features shrinking into the deep sub-micron range, so the challenge of defect isolation has become more difficult. Many failure analysis (FA) techniques using optical/electron beam and scanning probe microscopy (SPM) have been developed to improve the capability of defect isolation. SPM provides topographic imaging coupled with a variety of material characterization information such as thermal, magnetic, electric, capacitance, resistance and current with nano-meter scale resolution. Conductive atomic force microscopy (C-AFM) has been widely used for electrical characterization of dielectric film and gate oxide integrity (GOI). In this work, C-AFM has been successfully employed to isolate defects in the contact level and to discriminate various contact types. The current mapping of C-AFM has the potential to identify micro-leaky contacts better than voltage contrast (VC) imaging in SEM. It also provides I/V information that is helpful to diagnose the failure mechanism by comparing I/V curves of different contact types. C-AFM is able to localize faulty contacts with pico-amp current range and to characterize failure with nano-meter scale lateral resolution. C-AFM should become an important technique for IC fault localization. FA examples of this technique will be discussed in the article.

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