Synthesis, crystal structure and photoluminescence properties of novel far-red-emitting SrLaZnSbO6:Mn4+ double-perovskite phosphors for plant cultivation LEDs

Theoretical calculations and photoluminescence properties of Sr4Al14O25:Mn4+ red phosphors doped with Li. Dalton Trans 2023;52:13983-13990. [PMID: 37740293 DOI: 10.1039/d3dt02281a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The absence of high-efficiency oxide red phosphors restricts the development of high-performance solid-state lighting. In this work, a series of Li+ doped Sr4Al14O25:Mn4+ (SAO-Li+) red phosphors were prepared. Theoretical calculation results indicate that Li+ is inclined to occupy the gap 2 position. The low concentration Li+ gap doping has almost no influence on the Sr4Al14O25 structure, and a 0.4 mol Li+-doped sample exhibits a pure phase with regular morphology. With increasing Li+ doping content, the luminescence intensities of phosphors increase first and then decrease. 0.4 mol is found to be the optimal concentration. The fluorescence lifetime continues to decrease with the increase in the Li+ doping content and a mutation occurs at 0.5 mol Li+. Phosphor doping with Li+ can improve the thermal quenching resistance. The WLED device encapsulated with SAO-0.4Li and YAG:Ce3+ phosphors prepared showed a correlated color temperature of 4667 K, a color rendering index of 82, and a light efficiency of 137.34 lm W-1 at a driving current of 20 mA. The above results indicate that the use of a SAO-0.4Li+ phosphor is expected for application in warm WLEDs.

Enhanced luminescence performances of BaLaMgTaO6:Mn4+ red phosphor by Bi3+, Ca2+ doping for indoor plant lighting supplementary LED

A new perovskite BaLaMgTaO₆:Mn⁴⁺ (BLMTO:Mn⁴⁺) red phosphor was synthesized for the first time via the high-temperature solid-state method. The emission band of the phosphor ranges from 650 to 750 nm, which matches well with the absorption band of P_FR and P_R. By doping of Bi³⁺ and Ca²⁺ ions in the BLMTO:Mn⁴⁺ phosphor, a 4.76-fold enhancement in the luminescence emission intensity was achieved. The optimized BLMTO:0.5%Mn⁴⁺, 1.5%Bi³⁺, 2%Ca²⁺ phosphor exhibited a high quantum efficiency of 65% and a high color purity of 98.1% with the chromaticity coordinate (CIE) at (0.733, 0.267). Finally, a LED device was fabricated with the BLMTO:0.5%Mn⁴⁺, 1.5%Bi³⁺, 2%Ca²⁺ phosphor for further agricultural lighting, which emits warm white light with a low color temperature of 3549 K. The result indicates that the BLMTO:Mn⁴⁺, Bi³⁺, Ca²⁺ phosphors have a potential for applications in agricultural cultivations.

An organic-inorganic hybrid K2TiF6 : Mn4+ red-emitting phosphor with remarkable improvement of emission and luminescent thermal stability

A new type of monoethanolamine (MEA) and Mn4+ co-doped KTF : MEAH+, Mn4+ (K2TiF6 : 0.1MEAH+, 0.06Mn4+) red emitting phosphor was synthesized by an ion exchange method. The prepared Mn4+ co-doped organic-inorganic hybrid red phosphor exhibits sharp red emission at 632 nm and the emission intensity at room temperature is 1.43 times that of a non-hybrid control sample KTF : Mn4+ (K2TiF6 : 0.06Mn4+). It exhibits good luminescent thermal stability at high temperatures, and the maximum integrated PL intensity at 150 °C is 2.34 times that of the initial value at 30 °C. By coating a mixture of KTF : MEAH+, Mn4+, a yellow phosphor (YAG : Ce3+) and epoxy resin on a blue InGaN chip, a prototype WLED (white light-emitting diode) with CCT = 3740 K and R a = 90.7 is assembled. The good performance of the WLED shows that KTF : MEAH+, Mn4+ can provide a new choice for the synthesis of new Mn4+ doped fluoride phosphors.

Sunlight-Activated Orange Persistent Luminescence from Bi-Doped SrBaZn2Ga2O7 for Warm-Color Optical Applications

A warm persistent luminescence (PersL) material SrBaZn₂Ga₂O₇:Bi³⁺ was prepared using the conventional high-temperature solid-phase reaction method. We first investigated the PersL properties of SrBaZn₂Ga₂O₇:Bi³⁺ in detail via PersL spectra, PersL excitation spectrum, PersL decay curves, and thermoluminescence (TL) spectra. The highlight of this study is that in addition to the 254 nm light source, the low-energy light source of 365 nm and sunlight can effectively excite electrons and charge traps, resulting in preferable orange PersL performance. The PersL decay time of the representative sample can last for 960 s after excitation by a 365 nm light source and 900 s after excitation by simulated sunlight. Meanwhile, the PersL color can be regulated by changing the excitation wavelength. In order to explain the infrequent PersL phenomena after different light source excitations, we recorded a series of TL spectra as a function of different light sources, different charging times, and different decay times to reveal the distribution of traps in the material and the influence of trap distribution on trapping and detrapping processes. This novel sunlight-activated orange PersL material is expected to promote the development of sunlight-activated PersL materials and expand potential applications in solar energy utilization and anticounterfeit marking.