| 11. |
- Sharma, Suchinder, 1982, et al.
(författare)
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Green persistent luminescence excitable by multiple wavelengths in the CaSc2O4:Ce3+ phosphor co-doped with Mg2
- 2018
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 196, s. 437-441
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Tidskriftsartikel (refereegranskat)abstract
- Calcium scandate (CaSc 2 O 4 ), when substituted with a small amount of the activator ion Ce 3+ to replace Ca 2+ , is a recently discovered green-emitting phosphor promising for solid-state lighting applications. The co-doping with aliovalent ions to compensate for the net positive charge, as induced by the Ce 3+ dopants, is a common approach to change the defect structure and tune the performance of the phosphor, but the underlying mechanisms are unclear. Here we investigate the effect of co-doping with charge-compensating Mg 2+ to substitute for Sc 3+ , using photoluminescence and thermoluminescence techniques. In comparison to the defect structure in Ce 3+ doped CaSc 2 O 4 , the co-doping with charge-compensating Mg 2+ leads to the formation of new traps. These traps are featured by activation energies in the range 0.58–0.64 eV, can be emptied at room temperature and show green long-lasting phosphorescence after excitation at 454, 340, and 254 nm, respectively. Analysis of the spectroscopic results in terms of a vacuum referred binding energy diagram allows us to reach at a plausible luminescence mechanism in {Ce 3+ /Ce 3+ Mg 2+ }-doped CaSc 2 O 4 .
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| 12. |
- Trave, Enrico, et al.
(författare)
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Control of silver clustering for broadband Er3+ luminescence sensitization in Er and Ag co-implanted silica
- 2018
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Ingår i: Journal of Luminescence. - : Elsevier. - 0022-2313 .- 1872-7883. ; 197, s. 104-111
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the optical properties of Er and Ag co-implanted silica slabs were investigated in order to shed light on the observed improvement of the rare-earth emission properties through a sensitization process activated by Ag implantation. A full ion implantation approach was adopted since it represents an effective way to create a thin doped layer, where luminescent Er ions can interact with Ag-related sensitizing species. The results evidenced that the sensitization process is effectively promoted in presence of Ag ultra-small structures, like few-atom aggregates or multimers, which can be already formed at the early stages of the metal clustering process. On the other hand, the precipitation of large, plasmonic clusters, occurring at high temperature post-Ag implantation annealing, produces a decrease of the fluorescence enhancement effect. Furthermore, it is suggested that the overall sensitization mechanism originates from an Ag-Er energy transfer that determines the possibility of a broadband photostimulation of the rare-earth ions, even by pumping in non-resonant excitation condition. Thanks to these features, the investigated Er and Ag co-implanted system can be considered for the realization of high-performing optical amplifiers in waveguide.
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| 13. |
- Visniakova, Sigita, et al.
(författare)
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Luminescent benzo- and naphthoquinolines : Synthesis and investigation of photophysical properties
- 2015
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Ingår i: Journal of Luminescence. - : Elsevier. - 0022-2313 .- 1872-7883. ; 167, s. 261-267
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to synthesise new luminescent small molecular weight benzo- and naphthoquinoline derivatives (based on already known synthons) with different substituents (chlorine, tetrazole, iminophosphorane and amine), to characterize them by ultraviolet photoelectron spectroscopy in air (UPS), luminescence and absorption photospectrometry and to investigate the changes in these properties resulted by differences of molecular structure. Measured values of the HOMO, the LUMO energy levels and optical band gap (E-g_opt) were in range E-HOMO = [ - 5, 9; - 5, 5] eV, E-LUMO = [ 3, 6; - 3] eV, E-g_opt = [2; 2, 8] eV. Most of the examined materials showed high intensity fluorescence reaching quantum yields of 49%. Fluorescence peaks of thermally evaporated layers distributed in range of lambda(Layer)=[477; 596] nm - from blue to orange colour while in chloroform solution remained in blue-green interval lambda(Solution)=[471;537] nm. Primary study results of electroluminescence indicate that the materials have a potential to be used in organic optoelectronics.
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| 14. |
- Yang, Liu, et al.
(författare)
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Enhanced luminous efficacy of transparent Ce3+ : YAG ceramics with “light-scattering centres” prepared by uniform Ce:Y2O3 submicron spheres for WLEDs
- 2019
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 216
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Tidskriftsartikel (refereegranskat)abstract
- Transparent Ce3+:YAG ceramics have great potentials in WLEDs due to their ultra-high thermal endurance property and thermal stability of luminescence. However, it is still a challenging issue to enhance their light extraction ability. In the study, the transparent Ce3+:YAG ceramics were fabricated using the uniform Ce:Y2O3 submicron spheres by a solid-state reactive sintering method under vacuum without any sintering additives. The content of the residual pores and grain boundaries, which acted as the "light-scattering centres" to improve the absorption of blue light, were adjusted by changing sintering temperature. The luminous efficacy of the WLED with the sample sintered at 1700 degrees C was as high as 104.6 lm/W, due to the appropriate quantity of the "light-scattering centres". The microstructures, transmittance, excitation and emission spectra, luminous characteristics of the samples were studied. The results showed that the preparation progress could significantly enhance the luminous efficacy in the WLED with transparent ceramics.
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