scholarly journals Edge stabilization in reduced-dimensional perovskites

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Li Na Quan ◽  
Dongxin Ma ◽  
Yongbiao Zhao ◽  
Oleksandr Voznyy ◽  
Haifeng Yuan ◽  
...  
Keyword(s):  
Structural Diversity ◽  
Continuous Illumination ◽  
Quantum Yields ◽  
Color Purity ◽  
Phosphine Oxides ◽  
Maximum Luminance ◽  
Light Emitting ◽  
Tunable Bandgap ◽  
Luminescence Color ◽  
Oxidative Attack

AbstractReduced-dimensional perovskites are attractive light-emitting materials due to their efficient luminescence, color purity, tunable bandgap, and structural diversity. A major limitation in perovskite light-emitting diodes is their limited operational stability. Here we demonstrate that rapid photodegradation arises from edge-initiated photooxidation, wherein oxidative attack is powered by photogenerated and electrically-injected carriers that diffuse to the nanoplatelet edges and produce superoxide. We report an edge-stabilization strategy wherein phosphine oxides passivate unsaturated lead sites during perovskite crystallization. With this approach, we synthesize reduced-dimensional perovskites that exhibit 97 ± 3% photoluminescence quantum yields and stabilities that exceed 300 h upon continuous illumination in an air ambient. We achieve green-emitting devices with a peak external quantum efficiency (EQE) of 14% at 1000 cd m−2; their maximum luminance is 4.5 × 104 cd m−2 (corresponding to an EQE of 5%); and, at 4000 cd m−2, they achieve an operational half-lifetime of 3.5 h.

scholarly journals New Phosphine Oxides as High Performance Near- UV Type I Photoinitiators of Radical Polymerization

Molecules ◽  
2020 ◽  
Vol 25 (7) ◽  
pp. 1671 ◽  
Author(s):  
Céline Dietlin ◽  
Thanh Tam Trinh ◽  
Stéphane Schweizer ◽  
Bernadette Graff ◽  
Fabrice Morlet-Savary ◽  
...  
Keyword(s):  
Light Absorption ◽  
High Performance ◽  
Uv Light ◽  
Quantum Yields ◽  
Type I ◽  
Phosphine Oxides ◽  
Absorption Properties ◽  
Light Emitting ◽  
Uv Visible ◽  
Led Irradiation

Carbazole structures are of high interest in photopolymerization due to their enhanced light absorption properties in the near-UV or even visible ranges. Therefore, type I photoinitiators combining the carbazole chromophore to the well-established phosphine-oxides were proposed and studied in this article. The aim of this article was to propose type I photoinitiators that can be more reactive than benchmark phosphine oxides, which are among the more reactive type I photoinitiators for a UV or near-UV light emitting diodes (LED) irradiation. Two molecules were synthesized and their UV-visible light absorption properties as well as the quantum yields of photolysis and photopolymerization performances were measured. Remarkably, the associated absorption was enhanced in the 350–410 nm range compared to benchmark phosphine oxides, and one compound was found to be more reactive in photopolymerization than the commercial photoinitiator TPO-L for an irradiation at 395 nm.

Interfacial engineering for highly efficient quasi-two dimensional organic–inorganic hybrid perovskite light-emitting diodes

2019 ◽  
Vol 7 (15) ◽  
pp. 4344-4349 ◽  
Author(s):  
Qing-Wei Liu ◽  
Shuai Yuan ◽  
Shuang-Qiao Sun ◽  
Wei Luo ◽  
Yi-Jie Zhang ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Metal Halide ◽  
Color Purity ◽  
Two Dimensional ◽  
Inorganic Hybrid ◽  
Light Emitting ◽  
Interfacial Engineering ◽  
Tunable Bandgap ◽  
Hybrid Perovskite ◽  
High Color Purity

Metal halide-based perovskites are regarded as promising candidates for light-emitting diodes (LEDs) owing to their high color purity, tunable bandgap and solution processability.

scholarly journals High-performance quasi-2D perovskite light-emitting diodes: from materials to devices

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Li Zhang ◽  
Changjiu Sun ◽  
Tingwei He ◽  
Yuanzhi Jiang ◽  
Junli Wei ◽  
...  
Keyword(s):  
Energy Transfer ◽  
High Performance ◽  
Light Emitting Diodes ◽  
Structural Characteristics ◽  
Quantum Yields ◽  
Research Directions ◽  
Light Emitting ◽  
Perovskite Materials ◽  
Quantum Confinement Effects ◽  
Semiconducting Properties

AbstractQuasi-two-dimensional (quasi-2D) perovskites have attracted extraordinary attention due to their superior semiconducting properties and have emerged as one of the most promising materials for next-generation light-emitting diodes (LEDs). The outstanding optical properties originate from their structural characteristics. In particular, the inherent quantum-well structure endows them with a large exciton binding energy due to the strong dielectric- and quantum-confinement effects; the corresponding energy transfer among different n-value species thus results in high photoluminescence quantum yields (PLQYs), particularly at low excitation intensities. The review herein presents an overview of the inherent properties of quasi-2D perovskite materials, the corresponding energy transfer and spectral tunability methodologies for thin films, as well as their application in high-performance LEDs. We then summarize the challenges and potential research directions towards developing high-performance and stable quasi-2D PeLEDs. The review thus provides a systematic and timely summary for the community to deepen the understanding of quasi-2D perovskite materials and resulting LED devices.

scholarly journals Solution-Processed OLEDs Based on Thermally Activated Delayed Fluorescence Copper(I) Complexes with Intraligand Charge-Transfer Excited State

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1125
Author(s):  
Teng Teng ◽  
Jinfan Xiong ◽  
Gang Cheng ◽  
Changjiang Zhou ◽  
Xialei Lv ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Density Functional ◽  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Functional Theory ◽  
Solution Processed ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Wide Range

A new series of tetrahedral heteroleptic copper(I) complexes exhibiting efficient thermally-activated delayed fluorescence (TADF) in green to orange electromagnetic spectral regions has been developed by using D-A type N^N ligand and P^P ligands. Their structures, electrochemical, photophysical, and electroluminescence properties have been characterized. The complexes exhibit high photoluminescence quantum yields (PLQYs) of up to 0.71 at room temperature in doped film and the lifetimes are in a wide range of 4.3–24.1 μs. Density functional theory (DFT) calculations on the complexes reveal the lowest-lying intraligand charge-transfer excited states that are localized on the N^N ligands. Solution-processed organic light emitting diodes (OLEDs) based on one of the new emitters show a maximum external quantum efficiency (EQE) of 7.96%.

High performance red phosphorescent organic electroluminescent devices with characteristic mechanisms by utilizing terbium or gadolinium complexes as sensitizers

2017 ◽  
Vol 5 (8) ◽  
pp. 2066-2073 ◽  
Author(s):  
Rongzhen Cui ◽  
Weiqiang Liu ◽  
Liang Zhou ◽  
Xuesen Zhao ◽  
Yunlong Jiang ◽  
...  
Keyword(s):  
High Performance ◽  
Light Emitting Diodes ◽  
Organic Light Emitting Diodes ◽  
Color Purity ◽  
Electroluminescent Devices ◽  
Light Emitting ◽  
Organic Light ◽  
Gadolinium Complexes ◽  
Organic Electroluminescent ◽  
High Color Purity

High performance sensitized organic light-emitting diodes with high color purity were obtained by utilizing terbium or gadolinium complexes as sensitizers.

65‐3: Quantum Dot Light‐emitting Diodes with High Color Purity RGB Cadmium‐Free Quantum Dots

2021 ◽  
Vol 52 (1) ◽  
pp. 953-956
Author(s):  
Tatsuya Ryowa ◽  
Yusuke Sakakibara ◽  
Tadashi Kobashi ◽  
Keisuke Kitano ◽  
Masaya Ueda ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Light Emitting Diodes ◽  
Color Purity ◽  
Light Emitting ◽  
High Color Purity

scholarly journals Device Modeling of Quantum Dot–Organic Light Emitting Diodes for High Green Color Purity

2021 ◽  
Vol 11 (6) ◽  
pp. 2828
Author(s):  
Byoung-Seong Jeong
Keyword(s):  
Quantum Dot ◽  
Emission Spectrum ◽  
Blue Light ◽  
Light Emitting Diodes ◽  
Organic Light Emitting Diodes ◽  
Color Purity ◽  
Wavelength Band ◽  
Light Emitting ◽  
Green Color ◽  
Organic Light

In this study, the optimal structure for obtaining high green color purity was investigated by modeling quantum dot (QD)–organic light-emitting diodes (OLED). It was found that even if the green quantum dot (G-QD) density in the G-QD layer was 30%, the full width at half maximum (FWHM) in the green wavelength band could be minimized to achieve a sharp emission spectrum, but it was difficult to completely block the blue light leakage with the G-QD layer alone. This blue light leakage problem was solved by stacking a green color filter (G-CF) layer on top of the G-QD layer. When G-CF thickness 5 μm was stacked, blue light leakage was blocked completely, and the FWHM of the emission spectrum in the green wavelength band was minimized, resulting in high green color purity. It is expected that the overall color gamut of QD-OLED can be improved by optimizing the device that shows such excellent green color purity.

scholarly journals Simple Synthesis of Red Iridium(III) Complexes with Sulfur-Contained Four-Membered Ancillary Ligands for OLEDs

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2599
Author(s):  
Meng-Xi Mao ◽  
Fang-Ling Li ◽  
Yan Shen ◽  
Qi-Ming Liu ◽  
Shuai Xing ◽  
...  
Keyword(s):  
Indium Tin Oxide ◽  
Quantum Yields ◽  
Rapid Preparation ◽  
Maximum Brightness ◽  
Ancillary Ligands ◽  
Light Emitting ◽  
Maximum Current ◽  
Electron Donating Groups ◽  
Sulfur Containing ◽  
Main Ligand

Phosphorescent iridium(III) complexes have been widely researched for the fabrication of efficient organic light-emitting diodes (OLEDs). In this work, three red Ir(III) complexes named Ir-1, Ir-2, and Ir-3, with Ir-S-C-S four-membered framework rings, were synthesized efficiently at room temperature within 5 min using sulfur-containing ancillary ligands with electron-donating groups of 9,10-dihydro-9,9-dimethylacridine, phenoxazine, and phenothiazine, respectively. Due to the same main ligand of 4-(4-(trifluoromethyl)phenyl)quinazoline, all Ir(III) complexes showed similar photoluminescence emissions at 622, 619, and 622 nm with phosphorescence quantum yields of 35.4%, 50.4%, and 52.8%, respectively. OLEDs employing these complexes as emitters with the structure of ITO (indium tin oxide)/HAT-CN (dipyra-zino[2,3-f,2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile, 5 nm)/TAPC (4,4′-cyclohexylidenebis[N,N-bis-(4-methylphenyl)aniline], 40 nm)/TCTA (4,4″,4″-tris(carbazol-9-yl)triphenylamine, 10 nm)/Ir(III) complex (10 wt%): 2,6DCzPPy (2,6-bis-(3-(carbazol-9-yl)phenyl)pyridine, 10 nm)/TmPyPB (1,3,5-tri(mpyrid-3-yl-phenyl)benzene, 50 nm)/LiF (1 nm)/Al (100 nm) achieved good performance. In particular, the device based on complex Ir-3 with the phenothiazine unit showed the best performance with a maximum brightness of 22,480 cd m−2, a maximum current efficiency of 23.71 cd A−1, and a maximum external quantum efficiency of 18.1%. The research results suggest the Ir(III) complexes with a four-membered ring Ir-S-C-S backbone provide ideas for the rapid preparation of Ir(III) complexes for OLEDs.

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