Investigation of Energy Transfer in a Blend of electroluminescent Conducting Polymers

With the aim of improving the photonic efficiency of an organic light emitting diode a blend of electroluminescent polymers, poly[9-vinylcarbarzole] (PVK) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) was prepared. The energy transfer in the blend was investigated through the comparison of absorption, photoluminescence (PL) and current-voltage (I-V) characteristics of the blend and standard polymers. The obtained results showed that energy transfer from PVK to MEH-PPV enable to form localized excited-state complexes (e.g. exciplexes) in MEH-PPV. The PL intensity of the blended polymers was enhanced as the relative content of MEH-PPV was increased, and particularly, the highest improved PL was observed for an weight fraction of 15 wt{\%} of MEH-PPV in PVK. Organic light emitting diodes made from these blends would exhibit a large photonic efficiency.

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Cohosts with efficient host-to-emitter energy transfer for stable blue phosphorescent organic light-emitting diodes

Journal of Materials Chemistry C ◽

10.1039/d1tc04680b ◽

2021 ◽

Author(s):

Soo-Ghang Ihn ◽

Eun Suk Kwon ◽

Yongsik Jung ◽

Jong Soo Kim ◽

Sungho Nam ◽

...

Keyword(s):

Energy Transfer ◽

High Performance ◽

Light Emitting Diode ◽

Organic Light Emitting Diodes ◽

Operating Voltage ◽

Light Emitting ◽

Organic Light Emitting Diode ◽

Organic Light ◽

Low Efficiency ◽

Blue Phosphorescent

We present a high-performance blue phosphorescent organic light-emitting diode exhibiting a low operating voltage (4.1 V), high external quantum efficiency (23.4%, at 500 cd m-2) with a low efficiency roll-off...

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Unravelling the electron injection/transport mechanism in organic light-emitting diodes

Nature Communications ◽

10.1038/s41467-021-23067-2 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Tsubasa Sasaki ◽

Munehiro Hasegawa ◽

Kaito Inagaki ◽

Hirokazu Ito ◽

Kazuma Suzuki ◽

...

Keyword(s):

Work Function ◽

Transport Mechanism ◽

Light Emitting Diodes ◽

Light Emitting Diode ◽

Electron Injection ◽

Organic Light Emitting Diodes ◽

Light Emitting ◽

Organic Light Emitting Diode ◽

Organic Light ◽

Materials Used

AbstractAlthough significant progress has been made in the development of light-emitting materials for organic light-emitting diodes along with the elucidation of emission mechanisms, the electron injection/transport mechanism remains unclear, and the materials used for electron injection/transport have been basically unchanged for more than 20 years. Here, we unravelled the electron injection/transport mechanism by tuning the work function near the cathode to about 2.0 eV using a superbase. This extremely low-work function cathode allows direct electron injection into various materials, and it was found that organic materials can transport electrons independently of their molecular structure. On the basis of these findings, we have realised a simply structured blue organic light-emitting diode with an operational lifetime of more than 1,000,000 hours. Unravelling the electron injection/transport mechanism, as reported in this paper, not only greatly increases the choice of materials to be used for devices, but also allows simple device structures.

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Effect of Double Hole-Transporting Structure on Color Purity of Blue Organic Light-Emitting Diodes (BOLED)

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.311.424 ◽

2013 ◽

Vol 311 ◽

pp. 424-429

Author(s):

Kan Lin Chen ◽

Chien Jung Huang ◽

Zong Jin Wu ◽

Chih Chieh Kang ◽

Wen Ray Chen ◽

...

Keyword(s):

Light Emitting Diode ◽

Organic Light Emitting Diodes ◽

Blue Color ◽

Color Purity ◽

Television System ◽

Light Emitting ◽

Organic Light Emitting Diode ◽

Organic Light ◽

Hole Transporting ◽

The Right

A blue organic light-emitting diode (OLED) with a double hole-transporting (DHT) structure has been developed. The blue color purity was improved by modulation the thickness of CBP layer. When the thicknesses of left CBP and right CBP are respectively 8 nm and 2 nm, the more pure blue coordinates are (0.155, 0.079), which are very close to the blue coordinates of the national television system committee (NTSC) standard (0.14, 0.08). Furthermore the current density, brightness and the luminous efficiency of device with the left CBP of 8 nm and the right CBP of 2 nm are respectively 144.7 mA/cm2, 1065 cd/m2 and 0.93 cd/A.

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High efficiency above 20% in polymeric thermally activated delayed fluorescent organic light-emitting diodes by a host embedded backbone structure

Polymer Chemistry ◽

10.1039/c9py00701f ◽

2019 ◽

Vol 10 (35) ◽

pp. 4872-4878 ◽

Cited By ~ 2

Author(s):

Yun Hwan Park ◽

Ho Jin Jang ◽

Jun Yeob Lee

Keyword(s):

High Efficiency ◽

Light Emitting Diodes ◽

Light Emitting Diode ◽

Organic Light Emitting Diodes ◽

Light Emitting ◽

Organic Light Emitting Diode ◽

Thermally Activated ◽

Highly Efficient ◽

Organic Light ◽

Backbone Structure

A highly efficient polymeric thermally activated delayed fluorescent (TADF) organic light-emitting diode was developed by synthesizing a copolymer with 9-vinylcarbazole (VCz) and TADF repeating units.

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A life estimation model applied to organic light-emitting diodes

Lighting Research and Technology ◽

10.1177/1477153518796265 ◽

2018 ◽

Vol 51 (5) ◽

pp. 764-773

Author(s):

JP Zhang ◽

Y Zong ◽

Y Meng ◽

WG Pan ◽

JS Tang

Keyword(s):

Light Emitting Diodes ◽

Light Emitting Diode ◽

Organic Light Emitting Diodes ◽

Light Emitting ◽

Decay Data ◽

Light Emitting Devices ◽

Organic Light Emitting Diode ◽

Organic Light ◽

Extrapolation Model ◽

Accelerated Life

For predicting life for light-emitting devices quickly and accurately, a novel life prediction model, namely an extrapolation model of accelerated life and stress, has been proposed. In this model, a Weibull function is employed to fit luminance decay data under multiple groups of accelerated stresses, and the corresponding accelerated life is obtained. By determination coefficients and root mean square errors, a power function is determined as an extrapolated function to describe the relationship between accelerated life and stress and the life of the light-emitting devices. For organic light-emitting diodes, three groups of constant-stress accelerated degradation tests were conducted by increasing current stress. An extrapolation model of accelerated life and stress was applied to process the collected luminance decay data and was evaluated by a careful comparison with organic light-emitting diode life. The results indicate that the self-designed experimental scheme for organic light-emitting diode is feasible and versatile; the predicted life is 17,113 hours, which is close to the service life derived from user feedback, and the relative error is only 2.2%. This shows that the extrapolation model of accelerated life and stress has high precision; the model reveals the expected law of luminance changing with time and intuitively depicts the life characteristics under accelerated stresses without conventional life tests. This will pave the way for a new method to predict and evaluate the life of modern light-emitting devices.

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High-resolution electrohydrodynamic jet printing of small-molecule organic light-emitting diodes

Nanoscale ◽

10.1039/c5nr03034j ◽

2015 ◽

Vol 7 (32) ◽

pp. 13410-13415 ◽

Cited By ~ 71

Author(s):

Kukjoo Kim ◽

Gyeomuk Kim ◽

Bo Ram Lee ◽

Sangyoon Ji ◽

So-Yun Kim ◽

...

Keyword(s):

High Resolution ◽

Small Molecule ◽

Light Emitting Diodes ◽

Light Emitting Diode ◽

Organic Light Emitting Diodes ◽

Light Emitting ◽

Organic Light Emitting Diode ◽

Organic Light ◽

Electrohydrodynamic Jet Printing ◽

Jet Printing

An electrohydrodynamic jet (e-jet) printed high-resolution (pixel width of 5 μm) small-molecule organic light-emitting diode (OLED) is demonstrated.

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Tetraphenylmethane-Based 1,3,4-Oxadiazole as Electron Transporting Materials in Organic Light-Emitting Devices

MRS Proceedings ◽

10.1557/proc-598-bb3.5 ◽

1999 ◽

Vol 598 ◽

Cited By ~ 1

Author(s):

Chin-Ti Chen ◽

Tzu-Yao J. Lin ◽

Hsiu-Chih Yeh ◽

Li-Hsin Jan ◽

Easwaramoorthy Balasubramaniam ◽

...

Keyword(s):

Glass Phase ◽

Molecular Design ◽

Light Emitting Diode ◽

Light Emitting ◽

Light Emitting Devices ◽

Organic Light Emitting Diode ◽

Organic Light ◽

Current Voltage ◽

Electron Transporting Layer ◽

Current Voltage Characteristics

ABSTRACTA series of tetrahedral tetramers of 2,5-diphenyl substituted 1,3,4-oxadiazole compounds were synthesized and characterized for electron-transporting layer (ETL) in organic light-emitting diode (OLED). The multiple-branch design of the oxadiazole tetramers intends to increase the melting temperature and to generate glass phase of the low molar mass derivative such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD). We observed temperatures of the glass phase transition for the oxadiazole tetramer with appropriate peripheral substituents, indicative of amorphous characteristics of the molecule in spite of highly symmetrical molecular framework. The luminescence-current-voltage characteristics of multilayer OLED devices containing the oxadiazole tetramer or PBD as ETL were examined to evaluate the efficiency of our multiple-branch molecular design.

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