- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Bandgap trimming and optical properties of Si <sub/>3</sub> N <sub/>4</sub> :Al microbelt phosphors for warm white light-emitting diodes
摘要： Si3N4:Al microbelts with tunable bandgap energy and resultant yellow-orange phosphors are prepared through a facile direct nitridation method. The bandgap energy of Si3N4:Al microbelts has been gradually trimmed from 2.58 eV to 2.67, 2.74 and 2.85 eV by regulating the Si/Al molar ratio from 1000 : 1 to 50 : 1. Si3N4:Al:Eu phosphors display a wide emission ranging from 500 to 800 nm when excited by a 450 nm blue LED light source. The crystal structure of Si3N4:Al microbelts is of the α-Si3N4 phase as characterized by X-ray diffraction, high-resolution TEM and crystal models. Si3N4:Al microbelts grow along the (012) stacking direction in a low doping concentration case and grow along the (011) stacking direction in a high doping concentration case. Theoretical calculation results show that Al prefers to occupy the low energy interstitial sites in the (012) plane. There are more substitutional sites in the (011) plane occupied by Al in the high doping concentration case with increasing the bandgap energy of Si3N4:Al. Warm white light emission has been achieved by precoating Si3N4:Al:Eu phosphors onto a blue LED chip, whose correlated color temperature (CCT) can be tailored from 3000 K to 6500 K by altering the phosphor amount, indicating a promising potential application of Si3N4:Al:Eu phosphors in warm white LEDs.
关键词： direct nitridation method,Si3N4:Al microbelts,tunable bandgap energy,yellow-orange phosphors,warm white LEDs
更新于2025-09-12 10:27:22
-
Facile synthesis of the desired red phosphor Li <sub/>2</sub> Ca <sub/>2</sub> Mg <sub/>2</sub> Si <sub/>2</sub> N <sub/>6</sub> :Eu <sup>2+</sup> for high CRI white LEDs and plant growth LED device
摘要： The red emission with suitable peak wavelength and narrow band is acutely required for high color rendering index (CRI) white LEDs without at the cost of the luminous efficacy. Herein, the Li2Ca2Mg2Si2N6:Eu2+ red phosphor was prepared with facile solid-state method using Ca3N2, Mg3N2, Si3N4, Li3N, and Eu2O3 as the safety raw materials under atmospheric pressure for the first time, which shows red emission peaking at 638 nm with full width at half maximum (FWHM) of 62 nm under blue light irradiation and becomes the desired red phosphor to realize the balance between luminous efficacy and high CRI in white LEDs. The morphology, structure, luminescence properties, thermal quenching behavior, and chromaticity stability of the Li2Ca2Mg2Si2N6:Eu2+ phosphor are investigated in detail. Concentration quenching occurs when the Eu2+ content exceeds 1.0 mol%, whereas high temperature photoluminescent measurements show a 32% drop from the room temperature efficiency at 423 K. In view of the excellent luminescence performances of Li2Ca2Mg2Si2N6:Eu2+ phosphor, a white LEDs with CRI of 91 as a proof-of-concept experiment was fabricated by coating the title phosphor with Y3Al5O12:Ce3+ on a blue LED chip. In addition, the potential application of the title phosphor in plant growth LED device was also demonstrated. All the results indicate that Li2Ca2Mg2Si2N6:Eu2+ is a promising red-emitting phosphor for blue-LED-based high CRI white LEDs and plant growth lighting sources.
关键词： Li2Ca2Mg2Si2N6:Eu2+,high CRI white LEDs,plant growth LED device,phosphor
更新于2025-09-11 14:15:04
-
Eu3+-doped fluoro-telluroborate glasses as red-emitting components for W-LEDs application
摘要： From 0.1 up to 2.5 mol% Eu3t-doped fluro-telluroborate glasses as red light-emitting components for white-light-emitting diodes (WLEDs) were investigated. Non-periodicity in the atomic arrangements was studied through the XRD pattern. The photoluminescence (PL) spectra were recorded under blue light (464 nm) excitation and analyzed. All the PL spectra exhibit an intense peak at 612 nm for 5D0 → 7F2 transition, revealing their red photoemission. Optimal PL emissions were achieved for 1.0 mol% Eu3t-doped sample. The CIE chromaticity coordinates for all the glasses (x ? ~0.69, y ? ~0.30) fall within the red color region. The J?O parameters (Ω2, Ω4) were calculated following the emission spectra of Eu3t-doped samples and the intensity parameters (Ω2>Ω4), as well as the high asymmetry ratio (R/O), indicate the low ionicity in all the studied glasses. Using the J-O parameters, several radiative features like total emission transition probability (AT), branching ratios (radiative (βR) & experimental (βexp)), stimulated emission cross-section (σEP), gain bandwidth (σEP × λeff), and optical gain (σEP × τrad) were evaluated. All the luminescence decay curves fit well to non-exponential function and decay times were decreased at Eu3t concentration >0.5 mol%. The evaluated σEP = 19.684 × 10?21 cm2, βexp = 0.759, τexp = 1.325 ms, minimum non-radiative relaxation, WNR = 296/s, and 60.78% of quantum efficiency (η) for 1.0 mol% Eu3t-doped glass for 5D0 → 7F2 transition indicates its promising features for red light-emitting optical devices and also as a red component in WLEDs.
关键词： Luminescence features,Decay lifetimes,Eu3t,White LEDs,Radiative properties,CIE chromaticity coordinates
更新于2025-09-11 14:15:04
-
Screening Approach for the Discovery of New Hybrid Perovskites with Efficient Photoemission
摘要： Owing to quantum confinement, low-dimensional hybrid perovskite materials have recently shown a great potential for applications in optoelectronics. Such compounds can exhibit broad- or narrow-band light emission, low-temperature solution processability, high thermal stability, and relatively high photoluminescence quantum yields (PLQY). However, the search for efficient phosphors with a specific set of characteristics remains difficult because the family of hybrid perovskites consists in an extremely large chemical system (i.e., different halides, metals, and organic molecules), and optical properties are not predictable prior to material synthesis and characterization. Here, is proposed a simple approach to screen a significant amount of new hybrid lead halide perovskites. The synthetic method by fast crystallization at low temperature enables the rapid identification of the materials exhibiting the targeted photoluminescence properties. This approach is tested for the discovery of hybrid lead halide perovskites with efficient white-light emission. Among 100 newly synthesized compounds, 5 exhibit intense white emission, and the in-depth characterization of a selected candidate shows high color rendering index (CRI) = 78 and a PLQY of 9%, which is equivalent to the record reported for hybrid perovskites. This compound exhibits a new structure type for warm white-light emitting hybrid perovskites with chains of corner-sharing PbX6.
关键词： screening,photoluminescence,hybrid perovskite,white LEDs
更新于2025-09-10 09:29:36
-
Structural and luminescence properties of Eu3+ doped LaAlO3 nanophosphors by hydrothermal method
摘要： A series of La1?xAlO3: xEu3+ (x = 0, 2, 4, 6 and 8 mol%) nanophosphors have been synthesized by a hydrothermal technique and were investigated by an X-ray powder diffractometer, field emission scanning electron microscopy, high-resolution transmission electron microscopy and fourier transform infrared spectroscopy. Further, photoluminescent studies have also been orderly explored under the near-ultraviolet light excitation. When excited with 395 nm, the Eu3+: LaAlO3 nanophosphors emission peaks observed at 579, 591, 620, 649 and 700 nm due to the 5D0→7Fj (J = 0–4) transitions of Eu3+ ions. The prominent emission peak was perceived at 620 nm, which associated to the 5D0→7F2 hypersensitive transition of Eu3+ ion. The optimum doping concentration of Eu3+ in LaAlO3 host is around 6 mol% and the concentration quenching effect is through the dipole–dipole interaction. The Commission International de I’Eclairage (CIE) color co-ordinates were determined from emission spectra and the values (x, y) were closer to National Television Standard Committee typical value of red emission. As an outcome, the prepared nanophosphors are highly suitable for red component of white light emitting devices.
关键词： white LEDs,nanophosphors,hydrothermal method,photoluminescence,LaAlO3:Eu3+
更新于2025-09-04 15:30:14