Investigation of 4,4′- bis [(N carbazole) styryl] biphenyl (BSB4) for a pure blue fluorescent OLED with enhanced efficiency nearing the theoretical limit

Abstract 4,4′-bis[(N-carbazole) styryl] biphenyl (BSB4 or BSBCz) is one of the widely studied organic fluorescent materials for blue organic electroluminescent devices in the recent times. In this work, BSB4 is used as a guest material to construct the host-guest matrix for the emissive layer (EML) of a pure blue fluorescent organic light-emitting diode (OLED). A pure blue emission suitable for display application with a Commission Internationale de l’Eclairage (CIE) coordinate of (0.147, 0.070) is achieved by the blue-shift of the emission spectrum of the host-guest matrix from that of the pristine guest (BSB4) molecules. The optimization of OLED structures is carried out by considering (i) charge balance in the emissive layer for high exciton density, and (ii) optical interference of generated light in the organic layers for increased light outcoupling. A thorough comparative study on the use of different combinations of widely used hole and electron transport layers to obtain charge balance in the EML of the OLED, thereby enhancing the external quantum efficiency (EQE) is shown. Optical interference effects in the fabricated OLEDs are analyzed by optical simulation of each device structure by transfer matrix method (TMM). With the optimized device structures, we are able to overcome the 2% EQE limit that has been reported so far for blue fluorescent OLEDs with BSB4 as light emitting material and achieve a maximum EQE of 4.08%, which is near to the theoretical limit of EQE for fluorescent OLEDs.

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Color Tunability of Blue Phosphors by Changing Cations for Near-UV InGaN-Based Light-Emitting Diode

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.986-987.156 ◽

2014 ◽

Vol 986-987 ◽

pp. 156-159

Author(s):

Yi Wen Zhu ◽

Fen Fen Hu ◽

Mei Li Zhou ◽

Ping Chen ◽

Zheng Liang Wang

Keyword(s):

Uv Light ◽

Light Emitting Diode ◽

Blue Emission ◽

Emission Spectra ◽

Luminescent Properties ◽

Blue Shift ◽

Ionic Radii ◽

Light Emitting ◽

Triclinic Structure ◽

The Difference

The serials of blue phosphors, CaAl2Si2O8: Eu2+ doped with different content Sr2+ and Mg2+ ions, were prepared by solid-state reaction at high temperature. And their structure and photo-luminescent properties were investigated. In Ca0.96-ySryAl2Si2O8: 0.04Eu2+ (y = 0.10, 0.30, 0.50, 0.70, 0.90) system, for y ≦ 0.03, all the compositions crystallize in triclinic structure of CaAl2Si2O8, and on further increase of y, the system undergoes a compositionally induced phase transition from triclinic to monoclinic structure. For Ca0.96-yMgyAl2Si2O8: 0.04Eu2+ (y = 0.10, 0.30, 0.50, 0.70, 0.90) system, for z ≦ 0.03, all the compositions are of triclinic structure of CaAl2Si2O8. With the further increase of z, other phase appears. The emission spectra of these phosphors show blue shift with the introduction of Sr2+ ions, and red shift with Mg2+ ions. The reason may be due to the difference ionic radii of Mg2+, Ca2+, Sr2+. These phosphors show excellent blue emission and broad excitation band in near-UV (ultraviolet) range. They may be potential phosphors for near-UV light-emitting diodes (LEDs).

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InP-Based Quantum Dot Light-Emitting Diode with a Blended Emissive Layer

ACS Energy Letters ◽

10.1021/acsenergylett.1c00351 ◽

2021 ◽

pp. 1577-1585

Author(s):

Moon Gyu Han ◽

Yeonkyung Lee ◽

Ha-il Kwon ◽

Heejae Lee ◽

Taehyung Kim ◽

...

Keyword(s):

Quantum Dot ◽

Light Emitting Diode ◽

Light Emitting ◽

Emissive Layer

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The Optical Properties of InGaN/GaN Nanorods Fabricated on (-201) β-Ga2O3 Substrate for Vertical Light Emitting Diodes

Photonics ◽

10.3390/photonics8020042 ◽

2021 ◽

Vol 8 (2) ◽

pp. 42

Author(s):

Jie Zhao ◽

Weijiang Li ◽

Lulu Wang ◽

Xuecheng Wei ◽

Junxi Wang ◽

...

Keyword(s):

Stark Effect ◽

Light Emitting Diodes ◽

Light Emitting Diode ◽

Strain Relaxation ◽

Blue Shift ◽

Peak Position ◽

Excitation Power ◽

Light Extraction Efficiency ◽

Excitation Power Density ◽

Light Emitting

We fabricated InGaN/GaN nanorod light emitting diode (LED) on (-201) β-Ga2O3 substrate via the SiO2 nanosphere lithography and dry-etching techniques. The InGaN/GaN nanorod LED grown on β-Ga2O3 can effectively suppress quantum confined Stark effect (QCSE) compared to planar LED on account of the strain relaxation. With the enhancement of excitation power density, the photoluminescence (PL) peak shows a large blue-shift for the planar LED, while for the nanorod LED, the peak position shift is small. Furthermore, the simulations also show that the light extraction efficiency (LEE) of the nanorod LED is approximately seven times as high as that of the planar LED. Obviously, the InGaN/GaN/β-Ga2O3 nanorod LED is conducive to improving the optical performance relative to planar LED, and the present work may lay the groundwork for future development of the GaN-based vertical light emitting diodes (VLEDs) on β-Ga2O3 substrate.

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Substantial efficiency enhancement in solution processed phosphorescent light emitting diode with polymer host: Efficient optimization of charge balance and processing conditions

Journal of Physics and Chemistry of Solids ◽

10.1016/j.jpcs.2022.110577 ◽

2022 ◽

pp. 110577

Author(s):

Dipjyoti Das ◽

Peddaboodi Gopikrishna ◽

Debasish Barman ◽

Ramesh Babu Yathirajula ◽

Parameswar Krishnan Iyer

Keyword(s):

Light Emitting Diode ◽

Processing Conditions ◽

Efficiency Enhancement ◽

Charge Balance ◽

Solution Processed ◽

Light Emitting ◽

Polymer Host

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Silicon Quantum Dot Light Emitting Diode at 620 nm

Micromachines ◽

10.3390/mi10050318 ◽

2019 ◽

Vol 10 (5) ◽

pp. 318 ◽

Cited By ~ 8

Author(s):

Hiroyuki Yamada ◽

Naoto Shirahata

Keyword(s):

Quantum Dot ◽

High Performance ◽

Light Emitting Diode ◽

Optically Active ◽

Driving Voltage ◽

Device Structure ◽

Light Emitting ◽

Naked Eye ◽

Turn On ◽

Silicon Quantum Dot

Here we report a quantum dot light emitting diode (QLED), in which a layer of colloidal silicon quantum dots (SiQDs) works as the optically active component, exhibiting a strong electroluminescence (EL) spectrum peaking at 620 nm. We could not see any fluctuation of the EL spectral peak, even in air, when the operation voltage varied in the range from 4 to 5 V because of the possible advantage of the inverted device structure. The pale-orange EL spectrum was as narrow as 95 nm. Interestingly, the EL spectrum was narrower than the corresponding photoluminescence (PL) spectrum. The EL emission was strong enough to be seen by the naked eye. The currently obtained brightness (∼4200 cd/m2), the 0.033% external quantum efficiency (EQE), and a turn-on voltage as low as 2.8 V show a sufficiently high performance when compared to other orange-light-emitting Si-QLEDs in the literature. We also observed a parasitic emission from the neighboring compositional layer (i.e., the zinc oxide layer), and its intensity increased with the driving voltage of the device.

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Efficient deep-blue non-doped organic light-emitting diode with improved roll-off of efficiency based on hybrid local and charge-transfer excited state

RSC Advances ◽

10.1039/c6ra15079a ◽

2016 ◽

Vol 6 (74) ◽

pp. 70085-70090 ◽

Cited By ~ 26

Author(s):

Haichao Liu ◽

Qing Bai ◽

Weijun Li ◽

Yachen Guo ◽

Liang Yao ◽

...

Keyword(s):

Excited State ◽

High Efficiency ◽

Light Emitting Diode ◽

Blue Emission ◽

Light Emitting ◽

Organic Light Emitting Diode ◽

Deep Blue ◽

Organic Light ◽

Slow Roll ◽

Donor Acceptor

Acceptor–donor–acceptor triphenylamine–phenanthroimidazole derivate (TPA–2PPI) servers as an emitter, whose device exhibits deep-blue emission, high efficiency and slow roll-off of efficiency.

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Numerical study on ITO surface modification technique to improve single emissive layer based organic light emitting diode performance

2016 9th International Conference on Electrical and Computer Engineering (ICECE) ◽

10.1109/icece.2016.7853896 ◽

2016 ◽

Cited By ~ 1

Author(s):

Riku Chowdhury ◽

Md. Rashedul Haq ◽

Md. Sarwar Uddin Chowdhury ◽

Sharmin Afrose ◽

Sukanta Paul

Keyword(s):

Surface Modification ◽

Numerical Study ◽

Light Emitting Diode ◽

Light Emitting ◽

Emissive Layer ◽

Organic Light Emitting Diode ◽

Organic Light ◽

Modification Technique

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Side-Emitting LED Lens Design for Generating Planar Lighting Source

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.364-366.152 ◽

2007 ◽

Vol 364-366 ◽

pp. 152-155

Author(s):

Yi Ting Sun ◽

Yu Nan Pao ◽

T.H. Lin

Keyword(s):

Horizontal Plane ◽

Light Emitting Diode ◽

Design Procedure ◽

Normal Direction ◽

Optical Simulation ◽

Lens Design ◽

Simulation Tool ◽

Light Emitting ◽

Led Light ◽

Simulation Results

Side-emitting LED (Light emitting diode) modulation lens is proposed here for generating planar lighting source that can be applied in many fields like LCD backlight or general lighting. The light emitted form the LED light source will be modulated by the proposed lens by the mechanism of multi-refraction. The optical simulation tool ASAP was used during the design procedure. Optimal lens dimension was designed to module 70 percent of the emitting energy to the angle range from 70 degree to 110 degree, the angle was calculated from the normal direction of the LED horizontal plane to the direction of the emitting light. The lens prototype was also fabricated and the optical performance was measured to verify the simulation results. Finally, the comparison between the optical simulation and the experiment performances is also disclosed.

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The Photoluminescence Behaviors of a Novel Reddish Orange Emitting Phosphor CaIn2O4:Sm3+Codoped with Zn2+or Al3+Ions

Journal of Nanomaterials ◽

10.1155/2015/969724 ◽

2015 ◽

Vol 2015 ◽

pp. 1-5 ◽

Cited By ~ 1

Author(s):

Jing Gou ◽

Dongyang Zhang ◽

Binxun Yu ◽

Jing Wang ◽

Shengzhong Liu

Keyword(s):

Light Emitting Diode ◽

Luminescence Properties ◽

Charge Balance ◽

Transfer Energy ◽

Light Emitting ◽

Ultraviolet Excitation ◽

Near Ultraviolet ◽

Chromaticity Coordinates ◽

Charge Transfer Absorption Band ◽

Reddish Orange

A novel reddish orange phosphor CaIn2O4:Sm3+codoped with Zn2+or Al3+ions was prepared by solid state reaction and their luminescence properties were investigated under near ultraviolet excitation. The strategy of Zn2+or Al3+ions codoping was used with the aim to improve the luminescence properties of CaIn2O4:Sm3+, but the concrete effects of the two ions is different. The introduction of Zn2+ions can produceZnIn'defects that favor charge balance in CaIn2O4:Sm3+to facilitate its photoluminescence. The effect of Al3+ions codoping can effectively transfer energy from charge-transfer absorption band to characteristic transition of Sm3+ions, utilizing more energy from host absorption for the photoluminescence of Sm3+ions. Based on these mechanisms, the luminescence intensity of CaIn2O4:0.6%Sm3+was enhanced to 1.59 times and 1.51 times when codoping amount of Zn2+and Al3+ions reached 0.6%. However, the chromaticity coordinates of CaIn2O4:0.6%Sm3+almost did not have any changes after Zn2+ions or Al3+ions codoping; those are still located at reddish orange region. The excellent luminescence properties of CaIn2O4:0.6%Sm3+,0.6%Zn2+and CaIn2O4:0.6%Sm3+,0.6%Al3+demonstrate that they both have potential application value as new-style reddish orange phosphors on light-emitting diode.

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