Search results for "luminescence."
showing 10 items of 1568 documents
Optical Properties of Irradiated Topaz Crystals
2015
The results of an investigation of UV-Visible absorption and photoluminescence spectra of colorless topaz before and after neutron irradiation, natural blue topaz from Ukraine, and yellow topaz are presented. We assume that the absorption band ~ 620 nm and broad emission band 300-700 nm in topaz crystals are associated with exchange interaction between a radiation defect (anion vacancies, which capture one or two electrons) and impurity ions Cr 3+ , Fe 3+ and Mn 2+ .
Emission of Rhodamine B in PMMA opals for luminescent solar concentrators
2012
In conventional luminescent solar concentrators (LSC) incident light is absorbed by luminophores and emitted isotropically. Most of the emitted light is trapped inside the LSC by total internal reflection and guided to solar cells at the edges. Light emitted towards the surfaces, however, is lost in the escape cone. Furthermore, when the luminophore emits light in its absorption range, light is lost due to reabsorption. To overcome these losses, we embed the luminescent material in photonic structures to influence the emission characteristics. Directional and spectral redistribution of emission is supposed to enhance the light guiding in LSCs and reduce reabsorption losses. For this purpose…
Photoluminescence Enhancement by Band Alignment Engineering in MoS 2 /FePS 3 van der Waals Heterostructures
2022
Single-layer semiconducting transition metal dichalcogenides (2H-TMDs) display robust excitonic photoluminescence emission, which can be improved by controlled changes to the environment and the chemical potential of the material. However, a drastic emission quench has been generally observed when TMDs are stacked in van der Waals heterostructures, which often favor the nonradiative recombination of photocarriers. Herein, we achieve an enhancement of the photoluminescence of single-layer MoS2 on top of van der Waals FePS3. The optimal energy band alignment of this heterostructure preserves light emission of MoS2 against nonradiative interlayer recombination processes and favors the charge t…
ChemInform Abstract: Luminescent Ionic Transition Metal Complexes for Light-Emitting Electrochemical Cells
2012
Higher efficiency in the end-use of energy requires substantial progress in lighting concepts. All the technologies under development are based on solid-state electroluminescent materials and belong to the general area of solid-state lighting (SSL). The two main technologies being developed in SSL are light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs), but in recent years, light-emitting electrochemical cells (LECs) have emerged as an alternative option. The luminescent materials in LECs are either luminescent polymers together with ionic salts or ionic species, such as ionic transition-metal complexes (iTMCs). Cyclometalated complexes of IrIII are by far the most utiliz…
Synthesis and luminescent properties of Mn-doped alpha-tricalcium phosphate
2021
This project has received funding from European Social Fund (project No 09.3.3-LMT-K-712-19-0069) under grant agreement with the Research Council of Lithuania (LMTLT). Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART². The World Federation of Scientists is highly acknowledged for the National Scholarship to AZ. © 2021. This work is licensed under a CC BY-NC-ND 4.0 license.
Push‐Pull Design of Bis(tridentate) Ruthenium(II) Polypyridine Chromophores as Deep Red Light Emitters in Light‐Emitting Electrochemical Cells
2013
Light-emitting electrochemical cells (LECs) with a simple device structure were prepared by using heteroleptic bis(tridentate) ruthenium(II) complexes [1](PF6)(2)-[3](PF6)(2) as emitters. The push-pull substitution shifts the emission energy to low energy, into the NIR region. The devices emit deep red light up to a maximum emission wavelength of 755 nm [CIE (International Commission on Illumination) coordinates: x = 0.731, y = 0.269 for [3](PF6)(2)], which, to the best of our knowledge, is the lowest emission energy for LECs containing bis(tridentate) ruthenium(II) complexes. A device structure of ITO/PEDOT:PSS/ruthenium(II) complex/Ag was used, and the thickness of the emitting layer was …
Exciton emission and defect formation in yttrium trifluoride
2005
Two intrinsic emission bands at 220 and 280 nm have been detected in nominally pure YF3 powders at 10 K. Excitation spectra for both emissions have a sharp peak at 12 eV near the edge of interband transition. Observed emissions are assigned to the radiative decay of self-trapped excitons in YF3. The strong thermal quenching of intrinsic luminescence was observed at temperature above 120 K. It was supposed that non-radiative decay of self-trapped exciton at high temperatures lead to defect formation in YF3. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Combination of single-molecule magnet behaviour and luminescence properties in a new series of lanthanide complexes with tris(pyrazolyl)borate and ol…
2020
A series of tris(pyrazolyl)borate mono-, di- and trinuclear complexes, [Tp2Ln]nX (Ln = Eu, Tb, Gd, Dy, Xn− = various mono-, bis- and tris(β-diketonates) has been prepared. The Tb3+ and Dy3+ complexes are luminescent single molecular magnets (SMM) and exhibit luminescence quantum efficiencies up to 73% for the Tb3+ and 4.4% for the Dy3+ compounds. Similar Eu3+ complexes display bright emission only at lower temperatures. The Dy3+ and Tb3+ complexes possess SMM behavior in a non-zero dc field at low temperatures, while the polynuclear Dy3+ complexes also show slow magnetic relaxation even in zero dc field up to 8 K. Ueff-values determined from dynamic magnetic measurements were up to 31 and 6…
Stable Green Electroluminescence from an Iridium Tris-Heteroleptic Ionic Complex
2012
An ionic tris-heteroleptic iridium complex gives green light-emitting electrochemical cells (LECs) with unprecedented performances for this part of the visible spectrum. The devices are very bright (>1000 cd m–2), efficient (∼3%), and stable (>55 h). The novel complex is prepared using a new and efficient synthetic procedure. We show that there is a mixed orbital formation originating from the two different orthometalating ligands resulting in photophysical properties that lie between those of its two bis-heteroleptic analogs. Therefore, tris-heteroleptic complexes provide new avenues for fine-tunning the emission properties and to bridge gaps between a series of bis-heteroleptic complexes.
UV light induced processes in pure and doped AlN ceramics
2021
The present research has been sponsored by the Latvian Council of Science , Grant No. lzp-2018/1-0361 “Research of luminescence mechanisms and dosimeter properties in prospective nitrides and oxides using TL and OSL methods “; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 73950 , project CAMART 2