Electroluminescence in Chalcogenide Nanocrystals and Nanocomposites

2014 ◽  
Vol 357 ◽  
pp. 127-169 ◽  
Author(s):  
Meera Ramrakhiani ◽  
Nitendra Kumar Gautam ◽  
Kamal Kushwaha ◽  
Sakshi Sahare ◽  
Pranav Singh
Keyword(s):  
Threshold Voltage ◽  
Light Emission ◽  
Emission Spectra ◽  
Nanocrystalline Powder ◽  
Research Groups ◽  
Size Quantization ◽  
Chemical Route ◽  
Quantization Effect ◽  
Powder Samples ◽  
Znse Nanocrystals

Several research groups have reported that nanocrystalline II-VI semiconductors show enhanced luminescence, increased oscillator strength and shorter response time. Nanocrystalline powder samples of CdS, CdSe, ZnS and ZnSe nanocrystals and their composites with PVA and PVK have been prepared by chemical route. SEM. TEM and AFM images indicate agglomeration of particles. XRD reveal the crystal structure and size in nanometer range and absorption spectra show increased band gap due to quantum confinement.The EL studies on nanocrystalline powder samples and nanocrystal/polymer composites have shown that the light emission starts at certain threshold voltage, different for different specimens and then increases with increasing voltage. It is found that smaller nanocrystals have lower threshold voltage and higher EL brightness. It is observed that nanocomposite give much higher electroluminescence starting at lower voltage and increasing very fast with the voltage as compared to nanocrystalline powder. The emission spectra are found to depend on the material, crystalline size and doping. Electroluminescence in undoped and doped chalcogenide nanocrystals and nanocomposites is reviewed in this paper. In nanosize regime, electroluminescence (EL) is governed by the size quantization effect. Contents of Paper

scholarly journals Effect of nanocrystals concentration on optical and luminescent properties of PVK:ZnSe nanocomposites

2018 ◽  
Vol 36 (3) ◽  
pp. 494-500 ◽  
Author(s):  
Kanupriya Sharma ◽  
Praveen Kumar ◽  
Gaurav Verma
Keyword(s):  
Low Cost ◽  
Emission Spectra ◽  
Spherical Shape ◽  
Luminescent Properties ◽  
Nanocomposite Films ◽  
Present System ◽  
Structure Property ◽  
Chemical Route ◽  
Znse Nanocrystals ◽  
Optical And Luminescent Properties

AbstractThis work presents a systematic study of the effect of ZnSe nanocrystals (NCs) concentration on the optical and luminescent properties of poly N-vinylcarbazole (PVK) polymer nanocomposites. The ZnSe nanocrystals were synthesized by a simple coprecipitation chemical route, while PVK:ZnSe nanocomposite films were fabricated using the spin coating technique. The samples were characterized by XRD, TEM, SEM, UV-Vis and fluorescence techniques. The X-ray diffraction and TEM studies confirmed the particle size, microstructure and spherical shape of the synthesized nanocrystals. The ZnSe nanocrystals in PVK caused a decrease in optical gap with increasing concentration of nanocrystals. The emission spectra exhibited augmentation in intensity up to 70 wt.% of nanoparticles while further addition resulted in a decrease in luminescence. The structure-property relationships obtained for the present system are important for developing low cost illumination devices.

Size quantization effect in water-dispersible LEEH capped ZnSe nanocrystals

2021 ◽  
Author(s):  
Ansuman Nayak ◽  
Sukanta Kumar Triapthy ◽  
Nilesh Dalai ◽  
Swagat Kumar Nayak ◽  
Duryodhan Sahu
Keyword(s):  
Size Quantization ◽  
Water Dispersible ◽  
Quantization Effect ◽  
Znse Nanocrystals ◽  
Size Quantization Effect

scholarly journals Light Emission by Nanoporous GaN Produced by a Top-Down, Nonlithographical Nanopatterning

2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
E. Kheirandish ◽  
N. A. Kouklin ◽  
J. Liang
Keyword(s):  
Light Emission ◽  
Electronic Devices ◽  
Emission Spectra ◽  
Temperature Dependent ◽  
Physical Mechanisms ◽  
Spectral Shifts ◽  
Nanopore Arrays ◽  
Bulk Gan ◽  
Pl Emission ◽  
Temperature Dependent Photoluminescence

Temperature-dependent photoluminescence (PL) spectroscopy is carried out to probe radiative recombination and related light emission processes in two-dimensional periodic close-packed nanopore arrays in gallium nitride (np-GaN). The arrays were produced by nonlithographic nanopatterning of wurtzite GaN followed by a dry etching. The results of Raman spectroscopy point to a small relaxation of the compressive stress of ~0.24 GPa in nanoporous vs. bulk GaN. At ~300 K, the PL emission is induced by excitons and not free-carrier interband radiative recombinations. An evolution of the emission spectra with T is confirmed to be mainly a result of a decay of nonexcitonic PL emission and less of spectral shifts of the underlying PL bands. A switching of excitonic PL regime observed experimentally was analyzed within the exciton recombination-generation framework. The study provides new insights into the behaviors and physical mechanisms regulating light emission processes in np-GaN, critical to the development of nano-opto-electronic devices based on mesoscopic GaN.

Modifications of Light Emission Spectra and Atomic Structure of Europium Molibdate Bulk Crystals Caused by High Pressure and Heat Treatment

2008 ◽  
Vol 55 (3) ◽  
pp. 1128-1132 ◽  
Author(s):  
S. Z. Shmurak ◽  
A. P. Kiselev ◽  
N. V. Klassen ◽  
V. V. Sinitsyn ◽  
I. M. Shmyt'ko ◽  
...  
Keyword(s):  
Heat Treatment ◽  
High Pressure ◽  
Atomic Structure ◽  
Light Emission ◽  
Emission Spectra ◽  
Bulk Crystals

scholarly journals Bioluminescent Properties of Semi-Synthetic Obelin and Aequorin Activated by Coelenterazine Analogues with Modifications of C-2, C-6, and C-8 Substituents

2020 ◽  
Vol 21 (15) ◽  
pp. 5446
Author(s):  
Elena V. Eremeeva ◽  
Tianyu Jiang ◽  
Natalia P. Malikova ◽  
Minyong Li ◽  
Eugene S. Vysotski
Keyword(s):  
Light Emission ◽  
Emission Spectra ◽  
Calcium Sensitivity ◽  
Kinetic Properties ◽  
Hydrogen Bond Network ◽  
Single Chain ◽  
Acid Environment ◽  
Bond Network ◽  
Low Efficiency ◽  
Protein Active Site

Ca2+-regulated photoproteins responsible for bioluminescence of a variety of marine organisms are single-chain globular proteins within the inner cavity of which the oxygenated coelenterazine, 2-hydroperoxycoelenterazine, is tightly bound. Alongside with native coelenterazine, photoproteins can also use its synthetic analogues as substrates to produce flash-type bioluminescence. However, information on the effect of modifications of various groups of coelenterazine and amino acid environment of the protein active site on the bioluminescent properties of the corresponding semi-synthetic photoproteins is fragmentary and often controversial. In this paper, we investigated the specific bioluminescence activity, light emission spectra, stopped-flow kinetics and sensitivity to calcium of the semi-synthetic aequorins and obelins activated by novel coelenterazine analogues and the recently reported coelenterazine derivatives. Several semi-synthetic photoproteins activated by the studied coelenterazine analogues displayed sufficient bioluminescence activities accompanied by various changes in the spectral and kinetic properties as well as in calcium sensitivity. The poor activity of certain semi-synthetic photoproteins might be attributed to instability of some coelenterazine analogues in solution and low efficiency of 2-hydroperoxy adduct formation. In most cases, semi-synthetic obelins and aequorins displayed different properties upon being activated by the same coelenterazine analogue. The results indicated that the OH-group at the C-6 phenyl ring of coelenterazine is important for the photoprotein bioluminescence and that the hydrogen-bond network around the substituent in position 6 of the imidazopyrazinone core could be the reason of different bioluminescence activities of aequorin and obelin with certain coelenterazine analogues.

Electrostatic Discharge Characteristics of InGaN/GaN Light-Emitting Diodes with Si-Doped Graded Superlattice

2015 ◽  
Vol 15 (10) ◽  
pp. 7733-7737 ◽  
Author(s):  
Kwanjae Lee ◽  
Cheul-Ro Lee ◽  
Jin Soo Kim ◽  
Jin Hong Lee ◽  
Kee Young Lim ◽  
...  
Keyword(s):  
Light Emission ◽  
Electrostatic Discharge ◽  
Light Emitting Diode ◽  
Emission Spectra ◽  
Small Variation ◽  
Injection Current ◽  
Light Emitting ◽  
Current Voltage ◽  
Gan Led ◽  
Si Doped

We report the influences of a Si-doped graded superlattice (SiGSL) on the electrostatic discharge (ESD) characteristics of an InGaN/GaN light-emitting diode (LED). For comparison, a conventional InGaN/GaN LED (C-LED) was also investigated. The luminous efficacy for the SiGSL-LED was 2.68 times stronger than that for the C-LED at the injection current of 20 mA. The resistances estimated from current–voltage (I–V) characteristic curves were 16.5 and 8.8 Ω for the C-LED and SiGSL-LED, respectively. After the ESD treatment at the voltages of 4000 and 6000 V, there was no significant change in the I–V curves for the SiGSL-LED. Also, there was small variation in the I–V characteristics for the SiGSL-LED at the ESD voltage of 8000 V. However, the I–V curves for the C-LED were drastically degraded with increasing ESD voltage. While the light emission was not observed at the injection current of 20 mA from the C-LED sample after the ESD treatment, the emission spectra for the SiGSL-LED sample were clearly measured with the output powers of 10.47, 9.66, and 7.27 mW for the ESD voltages of 4000, 6000, and 8000 V respectively.

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