scholarly journals Exploring the Effects of Bay Position Chlorination on the Emissive Properties of Chloro-(Chloro)n-Boron Subnaphthalocyanines for Light Emission.

2020 ◽  
Author(s):  
Saul T.E. Jones ◽  
Andrew J. Pearson ◽  
Jeremy D. Dang ◽  
Neil Greenham ◽  
Timothy Bender ◽  
...  
Keyword(s):  
Light Emission ◽  
Positive Impact ◽  
Synthetic Method ◽  
Nonradiative Recombination ◽  
Effective Energy ◽  
Recombination Rates ◽  
Light Emitting ◽  
Effective Energy Transfer ◽  
Photophysical Processes ◽  
Emission Fraction

<p><b>Abstract:</b> It has been previously found that through an established synthesis of the macrocycle boron subnaphthalocyanine (BsubNc) that random bay-position chlorination occurs and results in a mixed alloyed composition that cannot be separated; called chloro-(chloro<sub>n</sub>)-boron subnaphthalocyanines (Cl-Cl<sub>n</sub>BsubNcs). Through modifications of the synthetic method, amounts of the average bay-position chlorination can be varied. Cl-Cl<sub>n</sub>BsubNcs are fluorescent and therefore here we explore the effect of the amount of bay-position chlorination on the photoluminescent and electroluminescent properties of Cl-Cl<sub>n</sub>BsubNcs. Distinct from previous reports detailing the positive impact of higher average bay-position chlorination, we find that the photophysical processes important to OLEDs improve with lower average bay-position chlorination. A higher degree of bay-position chlorine shows higher nonradiative recombination rates, lower photoluminescence quantum efficiencies and a basic OLEDs exhibits a greater host emission fraction, implying less effective energy transfer. These results advance the consideration of subnaphthalocyanines for light-emitting and optoelectronic applications.</p>

scholarly journals Exploring the Effects of Bay Position Chlorination on the Emissive Properties of Chloro-(Chloro)n-Boron Subnaphthalocyanines for Light Emission.

2020 ◽  
Author(s):  
Saul T.E. Jones ◽  
Andrew J. Pearson ◽  
Jeremy D. Dang ◽  
Neil Greenham ◽  
Timothy Bender ◽  
...  
Keyword(s):  
Light Emission ◽  
Positive Impact ◽  
Synthetic Method ◽  
Nonradiative Recombination ◽  
Effective Energy ◽  
Recombination Rates ◽  
Light Emitting ◽  
Effective Energy Transfer ◽  
Photophysical Processes ◽  
Emission Fraction

<p><b>Abstract:</b> It has been previously found that through an established synthesis of the macrocycle boron subnaphthalocyanine (BsubNc) that random bay-position chlorination occurs and results in a mixed alloyed composition that cannot be separated; called chloro-(chloro<sub>n</sub>)-boron subnaphthalocyanines (Cl-Cl<sub>n</sub>BsubNcs). Through modifications of the synthetic method, amounts of the average bay-position chlorination can be varied. Cl-Cl<sub>n</sub>BsubNcs are fluorescent and therefore here we explore the effect of the amount of bay-position chlorination on the photoluminescent and electroluminescent properties of Cl-Cl<sub>n</sub>BsubNcs. Distinct from previous reports detailing the positive impact of higher average bay-position chlorination, we find that the photophysical processes important to OLEDs improve with lower average bay-position chlorination. A higher degree of bay-position chlorine shows higher nonradiative recombination rates, lower photoluminescence quantum efficiencies and a basic OLEDs exhibits a greater host emission fraction, implying less effective energy transfer. These results advance the consideration of subnaphthalocyanines for light-emitting and optoelectronic applications.</p>

HIGHLY EFFICIENT BLUE ELECTROLUMINESCENCE BASED ON AGGREGATION INDUCED EMISSION MATERIAL AS THE HOST

2013 ◽  
Vol 01 (03) ◽  
pp. 1340012
Author(s):  
XIAO YANG ◽  
SHAOQING ZHUANG ◽  
LEI WANG ◽  
JING HUANG ◽  
ZHEN LI
Keyword(s):  
Energy Transfer ◽  
High Efficiency ◽  
Effective Energy ◽  
Maximum Luminance ◽  
Device Structure ◽  
Light Emitting ◽  
Aggregation Induced Emission ◽  
Light Emitting Devices ◽  
Organic Light ◽  
Effective Energy Transfer

High-efficiency blue organic light-emitting devices (OLEDs) have been fabricated using tetraphenylethene (TPE)-based conjugated molecule TPE-2Cz, which exhibited aggregation induced emission (AIE) properties, as blue host material and BUBD-1 as dopant emitter. With an optimized device structure, the effective energy transfer from the AIE host to BUBD-1 was achieved. The optimized device exhibits the peak EL efficiencies of 10.3 cd/A, 5.4% and 9.8 lm/W, with Commission Internationale de l'Eclairage coordinates of (0.15, 0.31) and a maximum luminance of 14550 cd/m2.

Excitation and Recombination Processes in rare Earth Doped II–VI Semiconductors

1996 ◽  
Vol 422 ◽  
Author(s):  
M. Godlewski
Keyword(s):  
Energy Transfer ◽  
Rare Earth ◽  
Light Emission ◽  
Wide Band ◽  
Impact Excitation ◽  
Nonradiative Recombination ◽  
Wide Band Gap ◽  
Light Emitting ◽  
Transfer Processes ◽  
Recombination Processes

AbstractRare Earth (RE) doped II–VI semiconductors are currently used for production of thin film light emitting electroluminescence devices. The excitation and recombination processes in RE activated wide band gap II–VI semiconductors (ZnS, ZnSe, SrS and CaS) are reviewed. Mechanisms relevant for obtaining bright photoluminescence (energy transfer processes, RE ionisation and exciton binding), electroluminescence (impact excitation and impact ionisation) and cathodoluminescence are described based on the recent experimental results. Efficiency of the light emission from RE doped II–VI materials is limited by several processes of nonradiative recombination. The Auger-type energy transfer processes and electric field- or thermally-activated processes responsible for 4f-4f nonradiative recombination of RE ions are discussed.

Theoretical investigation of dihydroacridine and diphenylsulphone derivatives as thermally activated delayed fluorescence emitters for organic light-emitting diodes

RSC Advances ◽  
2015 ◽  
Vol 5 (64) ◽  
pp. 51586-51591 ◽  
Author(s):  
Xiaguang Zhang ◽  
Wei Shen ◽  
Dongmei Zhang ◽  
Yongzhen Zheng ◽  
Rongxing He ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Theoretical Investigation ◽  
Delayed Fluorescence ◽  
Organic Light Emitting Diodes ◽  
Effective Energy ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Organic Light ◽  
Effective Energy Transfer

Effective energy transfer between host and emitter, which includes singlet–singlet, singlet–triplet and triplet–triplet transfer, would occur.

Low-Temperature Operation of Green, Blue and UV InGaN/GaN Multiple-Quantum-Well Light-Emitting Diodes

2003 ◽  
Vol 764 ◽  
Author(s):  
X. A. Cao ◽  
S. F. LeBoeuf ◽  
J. L. Garrett ◽  
A. Ebong ◽  
L. B. Rowland ◽  
...  
Keyword(s):  
Quantum Well ◽  
Light Emitting Diodes ◽  
Multiple Quantum Well ◽  
Light Output ◽  
Localized States ◽  
Multiple Quantum ◽  
Nonradiative Recombination ◽  
Light Emitting ◽  
Temperature Range ◽  
Green Leds

Absract:Temperature-dependent electroluminescence (EL) of InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with peak emission energies ranging from 2.3 eV (green) to 3.3 eV (UV) has been studied over a wide temperature range (5-300 K). As the temperature is decreased from 300 K to 150 K, the EL intensity increases in all devices due to reduced nonradiative recombination and improved carrier confinement. However, LED operation at lower temperatures (150-5 K) is a strong function of In ratio in the active layer. For the green LEDs, emission intensity increases monotonically in the whole temperature range, while for the blue and UV LEDs, a remarkable decrease of the light output was observed, accompanied by a large redshift of the peak energy. The discrepancy can be attributed to various amounts of localization states caused by In composition fluctuation in the QW active regions. Based on a rate equation analysis, we find that the densities of the localized states in the green LEDs are more than two orders of magnitude higher than that in the UV LED. The large number of localized states in the green LEDs are crucial to maintain high-efficiency carrier capture at low temperatures.

scholarly journals Effect of Laser Irradiation on Emissivity of Flame-Generated Nanooxides

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2303
Author(s):  
Silvana De Iuliis ◽  
Roberto Dondè ◽  
Igor Altman
Keyword(s):  
Laser Irradiation ◽  
Light Emission ◽  
Energy Gap ◽  
Particle Temperature ◽  
Electron Excitation ◽  
Flame Spray ◽  
Energy Bands ◽  
Light Emitting ◽  
Spectral Behavior ◽  
The Difference

The application of pyrometry to retrieve particle temperature in particulate-generating flames strictly requires the knowledge of the spectral behavior of emissivity of light-emitting particles. Normally, this spectral behavior is considered time-independent. The current paper challenges this assumption and explains why the emissivity of oxide nanoparticles formed in flame can change with time. The suggested phenomenon is related to transitions of electrons between the valence and conduction energy bands in oxides that are wide-gap dielectrics. The emissivity change is particularly crucial for the interpretation of fast processes occurring during laser-induced experiments. In the present work, we compare the response of titania particles produced by a flame spray to the laser irradiation at two different excitation wavelengths. The difference in the temporal behavior of the corresponding light emission intensities is attributed to the different mechanisms of electron excitation during the laser pulse. Interband transitions that are possible only in the case of the laser photon energy exceeding the titania energy gap led to the increase of the electron density in the conduction band. Relaxation of those electrons back to the valence band is the origin of the observed emissivity drop after the UV laser irradiation.

scholarly journals Recent advancements and perspectives on light management and high performance in perovskite light-emitting diodes

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Shaoni Kar ◽  
Nur Fadilah Jamaludin ◽  
Natalia Yantara ◽  
Subodh G. Mhaisalkar ◽  
Wei Lin Leong
Keyword(s):  
High Performance ◽  
Light Propagation ◽  
Light Emission ◽  
Review Article ◽  
Rapid Progress ◽  
Light Emitting ◽  
Materials Engineering ◽  
Perovskite Materials ◽  
Light Management ◽  
Photon Recycling

Abstract Perovskite semiconductors have experienced meteoric rise in a variety of optoelectronic applications. With a strong foothold on photovoltaics, much focus now lies on their light emission applications. Rapid progress in materials engineering have led to the demonstration of external quantum efficiencies that surpass the previously established theoretical limits. However, there remains much scope to further optimize the light propagation inside the device stack through careful tailoring of the optical processes that take place at the bulk and interface levels. Photon recycling in the emitter material followed by efficient outcoupling can result in boosting external efficiencies up to 100%. In addition, the poor ambient and operational stability of these materials and devices restrict further commercialization efforts. With best operational lifetimes of only a few hours reported, there is a long way to go before perovskite LEDs can be perceived as reliable alternatives to more established technologies like organic or quantum dot-based LED devices. This review article starts with the discussions of the mechanism of luminescence in these perovskite materials and factors impacting it. It then looks at the possible routes to achieve efficient outcoupling through nanostructuring of the emitter and the substrate. Next, we analyse the instability issues of perovskite-based LEDs from a photophysical standpoint, taking into consideration the underlying phenomena pertaining to defects, and summarize recent advances in mitigating the same. Finally, we provide an outlook on the possible routes forward for the field and propose new avenues to maximally exploit the excellent light-emitting capabilities of this family of semiconductors.

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