Excellent luminescent thermal stability of Dy3+/Sm3+ co-activated multifunctional titanate single-phase phosphors

Nowadays, the development of phosphors with excellent luminescent thermal stability for various applications has become a research hotspot. Therefore, the Dy3+/Sm3+ co-activated multifunctional NaYTiO4 phosphors with excellent comprehensive performance in the field of non-contact optical measurement and white LED solid-state lighting were reported in this paper, and their crystal structure, elemental composition, optical bandgap and photoluminescence properties were systematically studied. Remarkably, the reason why NaYTiO4:Dy3+,Sm3+ phosphors achieved color-controlled emission from yellow to orange-red and even to white at the excitation wavelength of 363 nm was not based on the energy transfer process from Dy3+ to Sm3+ but on co-excitation. When the temperature reached 475 K, the luminescence intensity of the phosphor still maintained 96.75% of the initial intensity, demonstrating excellent thermal quenching property. Furthermore, the temperature sensing performance was evaluated by FIR technique according to the differential decreasing trend of Dy3+ and Sm3+ emission intensity with increasing temperature. Finally, we also certified the applicability of NaYTiO4:Dy3+,Sm3+ phosphors in white LEDs for indoor health lighting. These results indicate that NaYTiO4:Dy3+,Sm3+ multifunctional phosphors are promising dual functional luminescent platforms that can be used for non-contact optical thermometers and white LED device applications.

Electronic structure, colour-tunable emission and energy transfer in Li3Ba2Y3(WO4)8:Bi3+,Eu3+ phosphors for white light-emitting diodes

Solid-state phosphor-converted white light-emitting diodes (pc-WLEDs) are the leading trend of the lighting industry in the 21st century. To pursue high quality WLED lighting, the development of highly efficient phosphors with tunable luminescence has become a hot research topic. Herein, we reported for the first time on Bi3+/Eu3+-doped Li3Ba2Y3(WO4)8 phosphors that exhibited tunable emission and high energy transfer efficiency of 89.90% from Bi3+ to Eu3+. The phase purity, microstructure, electronic structure and photoluminescence properties of these phosphors were studied in detail. Bi3+ and Eu3+ were effectively doped in Li3Ba2Y3(WO4)8 with an optical bandgap of 3.81 eV. The band structure and density of states were quantitatively evaluated by density functional theory simulation. At an excitation wavelength of 342 nm, the Bi3+-doped phosphor achieved yellow-green emission. By alloying Eu3+ into Li3Ba2Y3(WO4)8:Bi3+, the luminescence gradually turned red due to the energy transfer from Bi3+ to Eu3+. Moreover, the activation energy of the prepared phosphor was 0.1897 eV, demonstrating excellent thermal stability. Eventually, by combining Li3Ba2Y3(WO4)8:4%Bi3+,4%Eu3+ and a blue-emitting BAM:Eu2+ phosphor with a 365 nm ultraviolet chip, a WLED device with a high colour rendering index (Ra) of 78.7, chromaticity coordinates of (0.3401, 0.3131) and correlated colour temperature of 5080 K was successfully achieved. This work provided new insights into the design and development of color-tunable phosphors for white LEDs.

Bright white light emission from lanthanide oxide LaGdO3 for LED lighting by Bi3+ to Eu3+ energy transfer

Phosphors with intrinsic white light emission are of great potential in constructing high-quality white LEDs (WLEDs). In this work, we propose the use of energy transfer from Bi3+ to Eu3+ ions for white light emission. A unique Bi3+-activated phosphor LaGdO3 (LGO):Bi3+ was generated using the conventional high-temperature solid-state process. An energy transfer was established by introducing Eu3+ into the phosphor composition. The emission colour of LGO:Bi3+,Eu3+ phosphors changes from cyan to white to orange-red depending on the Bi3+/Eu3+ doping proportion. The energy transfer between the Bi3+ and Eu3+ ions results from the dipole-dipole interaction. The LGO:Bi3+,Eu3+ phosphors were combined with a near-ultraviolet chip to successfully create a single-component WLED device with a colour-rendering index of 92.4. Our work demonstrates the energy transfer as a route for single-component white light emission and makes LGO:Bi3+,Eu3+ phosphors one of the candidate materials for near-ultraviolet lighting.

A novel red-emitting phosphor with an unusual concentration quenching effect for near-UV-based WLEDs

An unusual concentration quenching effect is caused by the anisotropic distribution of quenching centers in GdGaTi2O7:Eu3+.