Optimization Of Dopant Concentration Research Articles

Spectroscopic investigation of upconversion and downshifting properties LaF3:Tb3+,Yb3+: A dual mode green emitter nanophosphor

The optimization of dopant concentration in upconverting nanophosphor is a real problem because of distinct limits defined by surface quenching, energy transfer and cross relaxation phenomenon. In this work, LaF3 based nanophosphors with different doping concentration of Yb3+ and Tb3+ ions were prepared by coprecipitation route. Particles are formed in spherical shape with narrow size distribution i.e. in ∼50–80 nm range. The volume of LaF3 unit cell shrinks with the doping of Tb3+ and Yb3+, whereas no variation in its phase were observed. The nanophosphors exhibit characteristics of dual mode spectral emitter. Thus, irrespective of excitation source (i.e. either UV or NIR), the intense green emission at 541 nm was observed. The material LaF3 with optimized molar doping concentration of 5%Tb3+ and 10%Yb3+ shows intense green emission on excitation with either UV or IR light. The time resolve luminescence emission were studied to explore the probability of involved energy transfer process between two dopant ions.

Correction: 3T1R model and tuning of thermoluminescence intensity by optimization of dopant concentration in monoclinic Gd2O3:Er3+;Yb3+ co-doped phosphor.

Correction for '3T1R model and tuning of thermoluminescence intensity by optimization of dopant concentration in monoclinic Gd2O3:Er3+;Yb3+ co-doped phosphor' by Raunak Kumar Tamrakar et al., Phys. Chem. Chem. Phys., 2017, 19, 14680-14694.

Photonic crystal assisted up-converter based on Tb3+ / Yb3+ - Doped aluminosilicate glass

Great efforts have been made in the last few years to increase the energy efficiency of solar cells. Among several factors which influence their performance, the light harvesting efficiency is the most relevant factor. In order to reduce the transparency losses of sub-bandgap solar photons, especially for wide gap solar cell materials, the development of up-conversion (UC) coatings to transform near infrared (NIR) light into short-wavelength visible photons is clearly a suitable approach. In spite of recent advances, the development of UC materials involves techniques which are generally not cost effective. This work will primarily focus on the evaluation of UC luminescence in aluminosilicate glass phosphors co-doped with the Tb3+/Yb3+ ion pair and synthesized by sol-gel (SG), a technique which is especially adequate to the deposition of films. The optimization of dopant concentrations has also been investigated, together with the structural, morphological and UC emission study of the coatings obtained. Lastly, a potential demonstrator has been developed in the form of a 1-D photonic crystal (PC) microcavity, in order to integrate the spectral conversion function into a more complex but more efficient structure.

3T1R model and tuning of thermoluminescence intensity by optimization of dopant concentration in monoclinic Gd2O3:Er3+;Yb3+ co-doped phosphor.

Thermoluminescence property of a phosphor is an important parameter that helps to determine the use of a phosphor in various dosimetric applications. In this study, the thermoluminescence behaviour of a monoclinic Gd2O3:Er3+;Yb3+ nanophosphor was studied. Gd2O3:Er3+;Yb3+ nanophosphor was prepared using a combustion synthesis method. Structural characterization was carried out via X-ray diffraction and electron microscopy methods. Herein, thermoluminescence (TL) study and kinetic analysis of the UV- and gamma-irradiated phosphor was also carried out. The prepared phosphor exhibits two TL glow curves around 122 and 263 °C for UV excitation and 157 and 295 °C for gamma exposure. The effect of different parameters on the TL glow curve was investigated. The glow curve deconvolution function was applied on the tuned glow peak curve. The trapping parameters were determined for tuned glow curve peaks as well as for the deconvoluted peaks. Moreover, reproducibility of the sample was determined via 7 replicate TL measurements. The prepared sample shows good reproducibility for both UV and gamma exposure. A theoretical three trap and one recombination centre (3T1R) model was proposed to explain the concentration quenching effect on the thermoluminescence behaviour of the prepared sample.

Optimization of dopant concentration in Ho:KLu(WO4)2 laser achieving ∼70% slope efficiency

We report on optimization of the dopant concentration in Ho:KLu(WO4)2 lasers based on continuous-wave laser operation under resonant pumping by a home-made diode-pumped Tm:KLu(WO4)2 laser. The highest laser efficiency amounted to 67.6% and corresponded to a dopant level of 5 at.% Ho in KLu(WO4)2. The maximum output power reached 507 mW at a wavelength of 2080 nm.

Laser-silicon interaction for selective emitter formation in photovoltaics. II. Model applications

Laser doping is an attractive way to manufacture a selective emitter in high efficiency solar cells, but the underlying phenomena, which determine performance, are not well understood. The mathematical model developed in Part I solves the equations of conservation of mass, momentum, and energy and is used here to investigate the effects of processing parameters on molten zone geometry, average phosphorus dopant concentration, dopant profile shape, and sheet resistance. The empirically calculated sheet resistance values are in good agreement with independently measured sheet resistance values reported in the literature. Process maps for output power and travel speed show that molten zone geometry and sheet resistance are more sensitive to output power than travel speed. The highest molten zone depth-to-width aspect ratios and lowest sheet resistances for 532 nm laser beams are obtained at higher laser powers (>13 W) and lower travel speeds (<2 m/s). Once the power level is set, the travel speed can be varied for further optimization of dopant concentration and geometry.

Modeling of Tm,Ho:YAG and Tm,Ho:YLF 2-μm lasers and calculation of extractable energies

The development of a model for 2-mum laser operation in Tm, Ho:YAG and YLF crystals pumped in the near infrared is reported. This model, based on a simplified spectroscopic scheme, is fitted to a set of characterization experiments by means of three adjustable parameters. Results show that the excited-state populations are predicted with a relative accuracy of approximately 10% for a large range of pump levels. Using this model, we calculate the extractable energy on short-laser-pulse interactions for the two materials under different operation conditions. We study the sensitivity to pump duration and the optimization of dopant concentrations. We investigate the improvement of the extractable-energy efficiency with multiple-pulse operation. For double-pulse operation the improvement is approximately a factor of 1.5 and leads to overall extractable-energy efficiencies of 16% in YAG and 15% in YLF for an absorbed pump energy of 10 J cm(-3).