Luminescence Studies on Dy3+ Doped Calcium Aluminum Borosilicate (CABS) Glasses for White Light Emission and Applications in w-LEDs.

Dy3+ doped calcium aluminum borosilicate (CABS) glasses have been synthesized via quick melt quench technique. CABS: xDy3+ glasses (x = 0.1, 0.5, 1, 1.5 and 2 mol%) were subjected to various morphological and photoluminescence studies. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were conducted to study the structural and bonding nature of the undoped glass. The excitation spectra of Dy3+ doped CABS glasses under 574 nm emission show many sharp peaks amongst which the transition from 6H15/2 → 6P7/2 (351 nm) had the highest intensity. Under 351 nm excitation, glasses exhibit sharp peaks in the blue, yellow and red regions corresponding to the transitions 4F9/2 → 6H15/2, 6H13/2, 6H11/2 and 6H9/2 respectively. The dipole-dipole nature of the interaction between the Dy3+ ions is confirmed via Dexter theory and Inokuti-Hirayama (I-H) model. CIE coordinates estimated from the emission profiles of these glasses under 351 nm excitation fall in the white region. Considering that these glasses exhibit sharp visible emission under UV excitation, have stable yellow to blue (Y/B) ratios and fast decays with intense energy transfers, we propose to utilise these glasses for white light generation and other white light LED (w-LED) and solid-state lighting (SSL) applications.

Photoluminescence enhancement and excellent thermal stability of Ca2ZnSi2O7:Pr3+ red-emitting phosphors through charge compensator A+ (Li+, Na+ and K+) co-doping for w-LED applications.

The red-emitting Ca2ZnSi2O7:Pr3+ phosphor was synthesized via a solid-state method and alkali metal ions A+ (Li+, Na+, K+) were introduced to improve the photoluminescence performance of Pr3+. XRD results confirmed that the sample structure did not change markedly with appropriate Pr3+/A+ co-doping. Under the blue light excitation of 447 nm, the as-prepared Ca2ZnSi2O7:Pr3+ efficiently emitted a characteristic red luminescence peak at 601 nm. The luminescence intensity of Pr3+ was obviously enhanced with A+ co-doping due to the charge compensation effect and the emission intensity of Ca2ZnSi2O7:0.005Pr3+, 0.005Na+ reached 142.1% compared to Ca2ZnSi2O7:0.005Pr3+. Furthermore, at 210 °C the luminescence intensity of the Ca2ZnSi2O7:0.005Pr3+, 0.005Na+ phosphor remained at âˆ¼93% compared to at 30 °C, showing high thermal stability. The w-LED device packaged with Ca2ZnSi2O7:0.005Pr3+, 0.005Na+ produced a bright white emission. All these results indicated the potential application prospects of red-emitting Ca2ZnSi2O7:Pr3+, A+ phosphors in the field of white light-emitting diodes.

Structural, optical, and luminescence properties of Dy3+ -activated potassium calcium silicate phosphor for white light-emitting diodes.

A dysprosium (Dy3+ )-activated potassium calcium silicate (K4 CaSi3 O9 ) phosphor was prepared using a solid-state synthesis route. The phosphor had a cubic structure with the space group Pa 3 ¯ as confirmed using X-ray diffraction (XRD) measurements. Details of surface morphology and elemental composition of the as-synthesized undoped KCS phosphor was obtained using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy. The chemical structure as well as the vibrational modes present in the as-prepared KCS phosphor was analyzed using Fourier transform infrared (FT-IR) spectroscopy. Diffuse reflectance spectra (DRS) were used to determine the optical bandgap of the phosphors and were found to be in the optical range 3.52-3.71 eV. Photoluminescence (PL) spectra showed intense yellow emission corresponding to the 4 F9/2 →6 H13/2 transition under 350 nm excitation. Commission International de l'Eclairage colour chromaticity coordinates were evaluated using the PL spectral data lie within the white region. Dexter theory and the Inokuti-Hirayama (I-H) model were applied to study the nature of the energy transfer mechanism in the as-prepared phosphors. The relatively high activation energy of the phosphors was evaluated using temperature-dependent PL (TDPL) data and confirmed the high thermal stability of the titled phosphor. The abovementioned results indicated that the as-prepared KCS:Dy3+ phosphor was a promising candidate for n-UV-based white light-emitting diodes.

Synthesis and novel emission properties of Bi3+ -doped Ca2 BO3 Cl phosphor for plant cultivation.

In the present work, a series of Bi3+ -activated Ca2 BO3 Cl phosphors was synthesized using the conventional high-temperature solid-state reaction method. The crystal structure of the prepared sample was determined to be monoclinic with space group P21/c. Scanning electron microscopy (SEM) analysis demonstrated the surface morphology with aggregated particles and sizes in the nano range. The presence of vibrational features and their luminescence characteristics were studied using Fourier transform infrared spectroscopy and photoluminescence (PL) techniques, respectively. At the 486 nm excitation wavelength, the PL spectrum revealed a sharp emission centred at 732 nm that was attributed to the 3 P1 →1 S0 transition of Bi3+ . The emission spectra exhibited the highest emission intensity at 0.5 mol% Bi3+ ion concentration, beyond this the emission intensity decreased due to the concentration quenching phenomenon attributed to multipolar interaction. The Commission Internationale de l'éclairage coordinates located at (0.7347, 0.2653) confirmed emission in the deep-red region with a colour purity of 99.98%. The obtained outcomes suggested that the reported material may be a promising candidate as a red-emitting phosphor for w-LEDs and plant growth applications.

Double Perovskite Mn4+-Doped La2CaSnO6/La2MgSnO6 Phosphor for Near-Ultraviolet Light Excited W-LEDs and Plant Growth.

Non-rare earth doped oxide phosphors with far-red emission have become one of the hot spots of current research due to their low price and excellent physicochemical stability as the red component in white light-emitting diodes (W-LEDs) and plant growth. Herein, we report novel Mn4+-doped La2CaSnO6 and La2MgSnO6 phosphors by high-temperature solid-phase synthesis and analyzed their crystal structures by XRD and Rietveld refinement. Their excitation spectra consist of two distinct excitation bands with the dominant excitation range from 250 to 450 nm, indicating that they possess strong absorption of near-ultraviolet light. Their emission is located around 693 and 708 nm, respectively, and can be absorbed by the photosensitive pigments Pr and Pfr, proving their great potential for plant growth. Finally, the prepared samples were coated with 365 nm UV chips to fabricate far-red LEDs and W-LEDs with low correlation color temperature (CCT = 4958 K/5275 K) and high color rendering index (Ra = 96.4/96.6). Our results indicate that La2CaSnO6:Mn4+ and La2MgSnO6:Mn4+ red phosphors could be used as candidate materials for W-LED lighting and plant growth.

Structure and luminescence investigation of Gd3+-sensitized perovskite CaLa4Ti4O15:Eu3+: A novel red-emitting phosphor for high-performance white light-emitting diodes and plants lighting.

A novel perovskite CaLa4Ti4O15:Eu3+ red-emitting phosphor was synthesized via a sol-combustion method, and Gd3+ was further co-doped into structure to improve the luminescence performance. The effects of Eu3+ doping and Gd3+ co-doping concentrations on the microstructure and luminescence properties were investigated. The red emission peaks of as-prepared phosphors originate from the 5D0→7Fj electron transitions of Eu3+ ions. Under 273 nm excitation, the luminescence intensity of Eu3+ was significantly enhanced through the energy transfer between Gd3+ and Eu3+ in CaLa4Ti4O15, and the luminescence intensity was also improved even under the excitation of 394 nm. By combining red-emitting CaLa4Ti4O15:Eu3+, Gd3+ phosphor with commercial blue and green phosphors on n-UV chip (λ = 395 nm), an eye-friendly w-LEDs with appropriate correlated color temperature (4761 K) and high color rendering index (Ra = 93.1) has been realized. The electroluminescence spectrum of the packaged red LED have an excellent match with the PR absorption of plants. In addition, when introducing CaLa4Ti4O15:Eu3+, Gd3+ phosphor into a commercial w-LED with YAG:Ce3+, the adjustable chromaticity parameters like CCT and CRI values can be obtained. These results demonstrated that the as-prepared CaLa4Ti4O15:Eu3+, Gd3+ phosphor is an outstanding candidate as the red component for the application of w-LEDs and plants lighting.

Strategies for Designing Antithermal-Quenching Red Phosphors.

Nowadays, red phosphor plays a key role in improving the lighting quality and color rendering index of phosphor-converted white light emitting diodes (w-LEDs). However, the development of thermally stable and highly efficient red phosphor is still a pivotal challenge. Herein, a new strategy to design antithermal-quenching red emission in Eu3+, Mn4+-codoped phosphors is proposed. The photoluminescence intensity of Mg3Y2(1- y )Ge3O12:yEu3+, Mn4+ (0 ≤ y ≤ 1) phosphors continuously enhances with rising temperature from 298 to 523 K based on Eu3+ → Mn4+ energy transfer. For Mg3Eu2Ge3O12:Mn4+ sample, the integrated intensity at 523 K remarkably reaches 120% of that at 298 K. Interestingly, through codoping Eu3+ and Mn4+ in Mg3Y2Ge3O12, the photoluminescence color is controllably tuned from orangish-red (610 nm) to deep-red (660 nm) light by changing Eu3+ concentration. The fabricated w-LEDs exhibit superior warm white light with low corrected color temperature (CCT = 4848 K) and high color rendering index (R a = 96.2), indicating the promising red component for w-LED applications. Based on the abnormal increase in antistokes peaks of Mn4+ with temperatures, Mg3Eu2Ge3O12:Mn4+ phosphor also presents a potential application in optical thermometry sensors. This work initiates a new insight to construct thermally stable and spectra-tunable red phosphors for various optical applications.

Synthesis and Luminescence Properties of a Novel Green-Yellow-Emitting Phosphor BiOCl:Pr3+ for Blue-Light-Based w-LEDs.

The development of white-light-emitting diodes (w-LEDs) makes it meaningful to develop novel high-performance phosphors excited by blue light. Herein, BiOCl:Pr3+ green-yellow phosphors were prepared via a high-temperature solid-state reaction method. The crystal structure, luminescent properties, lifetime, thermal quenching behavior, and quantum yield were studied in detail. The BiOCl:Pr3+ phosphors presented several emission peaks located in green and red regions, under excitation at 453 nm. The CIE coordinates could be tuned along with the changed doping concentration with fair luminescence efficiency. The results also indicated that the optimized doping concentration of Pr3+ ions was at x = 0.0075 because of the concentration quenching behavior resulting from an intense exchange effect. When the temperature reached 150 °C, the intensity of the emission peak at 495 nm could remain at 78% of that at room temperature. The activation energy of 0.20 eV also confirmed that the BiOCl:Pr3+ phosphor exhibited good thermal stability. All these results indicate that the prepared products have potential to be used as a high-performance green-yellow-light-emitting phosphor for blue-light-based w-LEDs.

Tb3+, Eu3+ Co-doped CsPbBr3 QDs Glass with Highly Stable and Luminous Adjustable for White LEDs.

Herein, we have introduced rare-earth cations Tb3+ and Eu3+ into CsPbBr3 QDs glass by conventional melt-quenching. Rare-earth cations like Tb3+ emit green light, causing the main peak of bromide lead cesium to exhibit some redshift, owing to the energy transfer between CsPbBr3 and Tb3+. To achieve adjustable light, Eu3+ emits red light, which was doped in this glass with different proportions to solve the problem of red deficiency. More importantly, Tb3+ and Eu3+ co-doped CsPbBr3 QDs glass shows a series of desirable characteristics due to the energy transfer between Tb3+ and Eu3+. Interestingly, the blue light radiated by blue chip can excite Tb3+, Eu3+, and CsPbBr3 perovskite effectively. We acquired high-performance white light-emitting diodes with color-rendering index, color coordinate transformation, and luminous efficiency of 85.7, 4945 K, and 63.21 lm/W under the current of 20 mA. This acquired Tb3+, Eu3+ co-doped CsPbBr3 QDs glass proved the significant feasibility of luminescent materials in solid warm light source.

Synthesis and luminescence characterization of a new yellowish-orange phosphor: Ba2 B10 O17 :Sm3.

A new yellowish-orange emitting phosphor, Ba2 B10 O17 :Sm3+ for use as a white light-emitting diode (W-LED) was synthesized by a solid-state reaction method. The X-ray diffraction results indicated that a pure Ba2 B10 O17 material was obtained. As a potential yellowish-orange luminescent material for W-LEDs, the Ba2 B10 O17 :Sm3+ phosphor could be excited effectively by near-ultraviolet (n-UV) light and exhibited yellowish-orange emission centered at 560 nm corresponding to the 4 G5/2  â†’ 6 H5/2 transition of Sm3+ ions. The optimum concentration of Sm3+ ions in Ba2 B10 O17 , critical transfer distance (Ra) and concentration quenching mechanism of the presented phosphor were investigated. Moreover, CIE chromaticity coordinates and color purity performance of the Ba2 B10 O17 :Sm3+ phosphor were also discussed. The present work suggests that the Ba2 B10 O17 :Sm3+ phosphor has potential as a type of yellowish-orange emitting phosphor. Copyright © 2016 John Wiley & Sons, Ltd.