Ultrapure single-band red upconversion luminescence in Er3+ doped sensitizer-rich ytterbium oxide transparent ceramics for solid-state lighting and temperature sensing

Sr4Al14O25:Li+,Mn4+ phosphor-in-glass film: erosion behavior and luminescence property

At present, phosphor-in-glass is regarded as a superior encapsulation material substituting for organic materials to resolve the poor thermal stability of WLEDs. However, the serious erosion reaction between commercial red phosphor and the glass matrix restricts the development and application of red phosphor-in-glass. In this work, a novel Sr4Al14O25:Li+,Mn4+ (SAO) red phosphor-in-glass film (PiGF) with precursor glass xB2O3-(85 - x)Bi2O3-5Al2O3-10CaO was prepared using a low-temperature sintering technique. Crystallization was observed in the precursor glass with 40% and 45% B2O3 content at 570 °C for 30 min, with the crystalline phase mainly being Bi4B2O9. The glass transition temperature gradually increases from 420 to 496 °C with an increase in B2O3 content from 40 to 60%. The DSC simulation and experimental results show that the degree of erosion of SAO phosphors decreases with an increase in B2O3 content from 50 to 60% and with an increase in the co-sintering temperature from 570 to 590 °C, while the glass surface smoothness of the PiGFs decreases with increasing B2O3 content. 55% B2O3 and 570 °C are the optimal parameters. The PL and PLE of the PiGFs show that the luminous intensity increases and then decreases with increasing B2O3 content, with 55% B2O3 also being the optimal value. The PiGF shows a quantum efficiency of 46.62%, and the luminous intensity maintains 85.1% of its initial intensity at 348 K.

Blue-excitable orange-red-emitting M3Y(PO4)3:Pr3+ (M = Ba, Sr, Ca) phosphors for multifunctional applications

Research on multifunctional luminescent materials has become an emerging trend for new applications of optical sensing, monitoring, anticounterfeiting, lighting, etc. Herein, a library of Pr3+-doped M3Y(PO4)3 (M = Ba, Sr, Ca) phosphors was prepared for careful spectroscopic studies in potential lighting and optical temperature sensing applications. With the help of density functional theory calculation, diffuse reflectance spectra, and steady/dynamic photoluminescence spectra, the effects of alkaline earth metals on the fluorescence properties of M3Y(PO4)3:Pr3+ were studied systematically. Under the excitation of blue ∼ 445 nm, orangish-red fluorescence of approximately 602 nm was efficiently detected due to Pr3+ 1D2 → 3H4 transition, which becomes stronger by regulating alkaline-earth elements from Ba to Sr and to Ca. An optimized Ca3Y(PO4)3:0.7%Pr3+ sample was validated with excellent thermal stability 89%@423 K and further applied to fabricate a white light emitting diode by combining with commercial YAG:Ce3+ phosphors on a 445 nm blue chip. Specifically, CIE chromaticity coordinates (0.3510, 0.3650) and correlated color temperature (∼ 4838 K) were obtained for an obvious improvement. Moreover, optical thermometry properties of Ca3Y(PO4)3:0.7%Pr3+ were explored on basis of Pr3+ 3P0-3P1 thermally coupled energy levels. Their fluorescence intensity ratios following the Boltzmann equation could be operated over 298-598 K with superior relative sensitivity ∼ 0.87% K-1 at 298 K. These interesting results for multifunctional luminescence will greatly promote the development of novel Pr3+-doped luminescent materials as well as the related photoelectric devices.

Mn2+/Mg2+ co-doped AlON ceramic with ultra-narrowband green emission combining high transparency toward a wide gamut backlight application

Narrowband green-emission, combined with superior physicochemical stability and thermal performance, is regarded as a common pursuit in backlight display applications. However, mainstream phosphor-converted materials composed of resin or silicone resin easily encounter the dilemma of thermal decomposition and chemical corrosion for practical use. To overcome this problem, in this work, Mn2+/Mg2+ co-doped AlON ceramic is successfully realized with ultra-narrowband green-emission and high transparency. The luminescent property of AlON: Mn2+-Mg2+ ceramic exhibits narrowband green emission centered at 509 nm with a full width at half maximum of 36 nm, which is smaller than the corresponding powder counterpart (44 nm). Moreover, AlON: Mn2+-Mg2+ ceramic presents a wide color gamut (103.6%) and high color purity (74%). Concurrently, high transmittance of this ceramic, at 82%, unveils a potential innovation in the display technology field. This work may facilitate the development of narrowband green light-emitting converters based on AlON: Mn2+-Mg2+ transparent ceramics in large color gamut backlight display applications.

Decolorization, spectral broadening, and luminescence enhancement in Tb:Y2O3 transparent ceramics through vacuum thermal reduction

Tb3+ is extensively employed in magneto-optical devices and luminescent materials owing to its distinctive physical properties. However, under certain conditions, trivalent Tb3+ readily undergoes oxidation to tetravalent Tb4+, significantly reducing the performance of devices containing Tb3+. In this Letter, we report a technique called dual-annealing (DA) post-treatment, which effectively solves Tb oxidation issues by utilizing the reducibility of the vacuum environment. High-quality Tb:Y2O3 transparent ceramics were prepared with in-line transmittance of ∼80% at 800 nm. Subsequently, the prepared ceramics were subjected to DA treatment. The optical, photoluminescence, radioluminescence, and x-ray imaging properties of DA samples were comprehensively compared with those of conventionally single-annealed (SA) samples. The coloration of Tb:Y2O3 transparent ceramics due to Tb4+ absorption was eliminated by DA. Notably, the DA sample showed a 3.28-fold increase in photoluminescence intensity and a 2.73-fold increase in radioluminescence intensity compared with the traditional SA sample. DA post-treatment enables Tb: Y2O3 transparent ceramics to achieve x-ray imaging capabilities. This Letter presents a simple, efficient, and universally applicable post-treatment technique expected to replace conventional hydrogen annealing in numerous scenarios.