Hydrophobic Organic Skin as a Protective Shield for Moisture-Sensitive Phosphor-Based Optoelectronic Devices

Reconstructing the Surface of K2SiF6:Mn4+ Phosphors toward Enhanced Moisture Resistance for White LED Applications

The K2SiF6:Mn4+ (KSFM) phosphor featuring efficient ultranarrow red emissions is an outstanding candidate for white light-emitting diode (WLED) applications. However, poor moisture resistance seriously affects its application performance. In this study, a two-step surface reconstruction strategy is proposed to dramatically enhance the moisture resistance of commercially available KSFM phosphors, involving treatment with H2NbF7 and subsequent hydrothermal treatment. The modified KSFM phosphor exhibits a high internal quantum efficiency (IQE) of 98.9% after the two-step surface treatment. Meanwhile, nearly 100% of the initial emission intensity is retained for the modified KSFM phosphor even after aging in high temperature (85 °C) and high relative humidity (85% RH) environments for 6 days, in sharp contrast to only 18.6% retention for the original KSFM phosphor. The relative emission intensity of the modified KSFM remains at 98.9% even after being immersed in water for 6 h. Additionally, the phosphor-converted LED fabricated with the modified KSFM phosphor demonstrated excellent long-term stability, retaining up to 97.9% of initial luminous efficacy after aging under 85 °C and 85% RH conditions for 500 h. The moisture-resistance mechanism is elucidated on the basis of spectroscopic analysis as well as structural and compositional characterization of the phosphor surface layer, which can be attributed to the formation of a robust Mn4+-rare shell with high crystalline quality following this two-step surface treatment. The findings contribute to the performance improvements of KSFM phosphors for industrial applications.

Ion exchange-assisted surface passivation toward highly stable red-emitting fluoride phosphors for light-emitting diodes

A facile and environmentally friendly ion exchange-assisted surface passivation (IASP) strategy is presented for synthesizing red emitting Mn4+-activated fluoride phosphors. A substantial, pristine Mn4+-free shell layer, applied as a coating to Mn4+ doped potassium fluorosilicate K2SiF6:Mn4+ (KSFM) phosphors, enhances both water resistance and luminescence efficiency. The stability test of fluoride in water at ambient temperature and boiling water demonstrates that IASP-treated KSFM phosphors are highly water resistant. Furthermore, both the negative thermal temperature (NTQ) fitting results and the photoluminescence (PL) decay confirm that the IASP process effectively passivates surface defects, leading to enhanced luminescence performance. The maximum internal quantum yield (QYi) of the IASP-KSFM phosphor is 94.24%. A white LED realized a high color rendering index (CRI) of 93.09 and luminous efficiency (LE) of 149.48 lm/W. This work presented a novel technique for the development of stable fluoride phosphors and has the potential to increase the use of KSFM phosphors in plant supplementary lighting systems and white light-emitting diodes.

Optical enhancement of highly efficient organic-inorganic oxyfluoride red phosphors via the cation co-doping strategy

Herein, a new organic cationic matrix [N(CH3)4]3MoO3F3 suitable for Mn4+ doping was constructed. Due to the large steric hindrance of N[CH3]4+ (TMA), charge compensation defects can be effectively prevented in the heterovalent Mn4+-doping process, and a high IQE (91.05%) was obtained. Through the cation co-doping strategy, Mg2+/Zn2+/Li+ cations were introduced into the Mo6+ cationic site, which improved the crystallinity of the matrix and reduced energy losses, so as to improve luminescence intensity, QE, thermal stability, water stability and other spectral properties. Meanwhile, [N(CH3)4]2TiF6:Mn4+ phosphors with the same TMA organic cation and equivalent Mn4+ doping were synthesized for comparison, and the effects of the Mg2+ cation co-doping strategy on the spectral properties of phosphors with different matrix types (fluoride/oxyfluoride) and substitution types (equivalent/non-equivalent) were analyzed. These findings provide the basis for the preparation of new luminescent materials. Furthermore, according to the optical properties exhibited by these phosphors, they are packaged into WLED devices with excellent photoelectric properties, which are suitable for indoor lighting and display fields.

Research progress on surface modifications for phosphors used in light-emitting diodes (LEDs)

Stable and efficient phosphors are highly important for light-emitting diodes (LEDs) with respect to their application in solid-state lighting, instead of conventional lamps for general lighting. However, some problems, like low stability, low photoluminescence (PL) efficiency, and serious thermal degradation, are commonly encountered in phosphors, limiting their applications in LEDs. Surface modifications for some phosphors commonly used in LED lighting, including fluoride, sulphide, silicate, oxide, nitride, and oxynitride phosphors, are presented in this review. By forming a protective surface layer, the stabilities against moisture and high temperature of fluoride- and sulphide-based phosphors were strengthened; by coating inorganic and organic materials around the particle surface, the PL efficiencies of silicate- and oxide-based phosphors were improved; by passivation treatment upon the phosphor surface, the thermal degradation of nitride- and oxynitride-based phosphors was reduced. Various technologies for surface modification are described in detail; moreover, the mechanisms of stability strengthening, PL efficiency improvement, and thermal degradation reduction are explained. In addition, embedding of phosphors in inorganic glass matrix, especially for quantum dots, is also introduced as an effective method to improve phosphor stability for LED applications. Finally, future developments of surface modification of phosphors are proposed.

Boosting Red Luminescence of Mn4+ in Tantalum Heptafluoride Based on an Ab Initio-Facilitated Sensitizer and Hydrophobic Surface Modification

A narrow-band red-light component is critical to establish high color rendition and a wide color gamut of phosphor-converted white-light-emitting diodes (pc-WLEDs). In this sense, Mn⁴⁺-doped K₂SiF₆ fluoride is the most successful material that has been commercialized. As with K₂SiF₆:Mn⁴⁺ phosphors, Mn⁴⁺-doped tantalum heptafluoride (K₂TaF₇:Mn⁴⁺) fulfills a similar luminescence behavior and has been brought in a promising narrow-band red phosphor. But the limited brightness and low moisture-resistant performances have inevitably blocked its practical application. Herein, we employed the density functional theory (DFT)-based ab initio estimation approach to quickly identify the proper sensitizer by systematically investigating the electronic-band coupling between the several possible sensitizers (Rb, Hf, Zr, Sn, Nb, and Mo) and the luminescent center (Mn). Combined with experimental results, Mo was demonstrated to be the optimal sensitizer, which resulted in a 60% enhancement of the emission. On the side, the moisture sensitivity has been effectively improved via grafting the hydrophobic octadecyltrimethoxysilane (ODTMS) layer on the phosphor surface. Through employing the K₂TaF₇:Mn⁴⁺,Mo⁶⁺@ODTMS composite as a red component, warm WLEDs with good performance were achieved with a correlated color temperature (CCT) of 4352 K, a luminous efficacy (LE) of 90.1 lm/W, and a color rendering index (Ra) of 83.4. In addition, a wide color gamut reaching up to 102.8% of the NTSC 1953 value could be realized. Aging tests at 85 °C and 85% humidity for 120 h on this device manifested that the ODTMS-modified phosphor had much better moisture stability than that of the unmodified one. These studies provided viable tools for optimizing Mn⁴⁺ luminescence in fluoride hosts.

Recent Research Progress of Mn4+-Doped A2MF6 (A = Li, Na, K, Cs, or Rb; M = Si, Ti, Ge, or Sn) Red Phosphors Based on a Core-Shell Structure

White light emitting diodes (WLEDs) are widely used due to their advantages of high efficiency, low electricity consumption, long service life, quick response time, environmental protection, and so on. The addition of red phosphor is beneficial to further improve the quality of WLEDs. The search for novel red phosphors has focused mainly on Eu²⁺ ion- and Mn⁴⁺ ion-doped compounds. Both of them have emissions in the red region, absorption in blue region, and similar quantum yields. Eu²⁺-doped phosphors possess a rather broad-band emission with a tail in the deep red spectral range, where the sensitivity of the human eye is significantly reduced, resulting in a decrease in luminous efficacy of WLEDs. Mn⁴⁺ ions provide a narrow emission band ~670 nm in oxide hosts, which is still almost unrecognizable to the human eye. Mn⁴⁺-doped fluoride phosphors have become one of the research hotspots in recent years due to their excellent fluorescent properties, thermal stability, and low cost. They possess broad absorption in the blue region, and a series of narrow red emission bands at around 630 nm, which are suitable to serve as red emitting components of WLEDs. However, the problem of easy hydrolysis in humid environments limits their application. Recent studies have shown that constructing a core-shell structure can effectively improve the water resistance of Mn⁴⁺-doped fluorides. This paper outlines the research progress of Mn⁴⁺-doped fluoride A₂MF₆ (A = Li, Na, K, Cs, or Rb; M = Si, Ti, Ge or Sn), which has been based on the core-shell structure in recent years. From the viewpoint of the core-shell structure, this paper mainly emphasizes the shell layer classification, synthesis methods, luminescent mechanism, the effect on luminescent properties, and water resistance, and it also gives some applications in terms of WLEDs. Moreover, it proposes challenges and developments in the future.

Nanocrystalline Iron Pyrophosphate-Regulated Amorphous Phosphate Overlayer for Enhancing Solar Water Oxidation

A rational regulation of the solar water splitting reaction pathway by adjusting the surface composition and phase structure of catalysts is a substantial approach to ameliorate the sluggish reaction kinetics and improve the energy conversion efficiency. In this study, we demonstrate a nanocrystalline iron pyrophosphate (Fe4(P2O7)3, FePy)-regulated hybrid overlayer with amorphous iron phosphate (FePO4, FePi) on the surface of metal oxide nanostructure with boosted photoelectrochemical (PEC) water oxidation. By manipulating the facile electrochemical surface treatment followed by the phosphating process, nanocrystalline FePy is localized in the FePi amorphous overlayer to form a heterogeneous hybrid structure. The FePy-regulated hybrid overlayer (FePy@FePi) results in significantly enhanced PEC performance with long-term durability. Compared with the homogeneous FePi amorphous overlayer, FePy@FePi can improve the charge transfer efficiency more significantly, from 60% of FePi to 79% of FePy@FePi. Our density-functional theory calculations reveal that the coexistence of FePi and FePy phases on the surface of metal oxide results in much better oxygen evolution reaction kinetics, where the FePi was found to have a typical down-hill reaction for the conversion from OH* to O2, while FePy has a low free energy for the formation of OH*.

Effect of multifunctional laser photoelectricity platform combined with hydroxychloroquine treatment sensitive facial skin

OBJECTIVE

To observe the clinical efficacy of a multifunctional laser photoelectric platform combined with hydroxychloroquine in the treatment of l sensitive facia skin.

METHODS

A total of 226 patients with sensitive facial skin treated from March 2019 to November 2021 were randomly divided into two groups.Both groups were given an external moisturizer (shumin moisturizer) once in the morning and once in the evening as basic skin care treatment for the disease. The control group received hydroxychloroquine sulfate tablets (0.2 g), twice a day; The observation group was treated with multifunctional laser photoelectric platform combined with hydroxychloroquine orally, and the clinical effects of the two groups were compared.

RESULTS

The effective rates of the observation group were 48.67%, 73.45% and 93.80% at the first, second and fourth weekend of treatment respectively, which were significantly higher than those of the control group (15.93%, 30.97% and 38.93%, respectively), with statistical significance (P<0.05).

CONCLUSION

On the basis of skin care with an external moisturizer, using a multifunctional laser photoelectric platform combined with hydroxychloroquine can significantly improve the clinical efficacy of facial sensitive skin, superior to hydroxychloroquine alone, with high safety and worthy of clinical application. This article is protected by copyright. All rights reserved.

Moisture-resistant Nb-based fluoride K2NbF7:Mn4+ and oxyfluoride phosphor K3(NbOF5)(HF2):Mn4+: synthesis, improved luminescence performance and application in warm white LEDs

Herein, high-efficiency Nb-based oxyfluoride K₃(NbOF₅)(HF₂):Mn⁴⁺ and fluoride K₂NbF₇:Mn⁴⁺ phosphors were successfully synthesized using different amounts of HF acid solutions by a simple co-precipitation method. XRD, SEM and EDS were used to characterize the crystal structure, morphology and elemental composition of the phosphors. The emission spectra, excitation spectra and luminescence decay curves were used to study the luminescence characteristics of the samples. The thermal stability of the phosphors was tested and the mechanism of temperature quenching was discussed. Meanwhile, the moisture resistance and application of the phosphors were investigated in detail. The results show that the K₃(NbOF₅)(HF₂):Mn⁴⁺ phosphor has stronger luminous intensity, lower color temperature, and better moisture resistance compared with the K₂NbF₇:Mn⁴⁺ phosphor. The correlated color temperature (CCT) and color rendering index (CRI) of warm white LEDs can be significantly improved by using the K₃(NbOF₅)(HF₂):Mn⁴⁺ (CCT = 3430 K, CRI = 87.3) phosphor as a red light component. So the K₃(NbOF₅)(HF₂):Mn⁴⁺ phosphor has broader application prospect in the field of warm white LEDs.

Enhancing Structural Rigidity via a Strategy Involving Protons for Creating Water-Resistant Mn4+-Doped Fluoride Phosphors

The poor water resistance property of a commercial Mn⁴⁺-activated narrow-band red-emitting fluoride phosphor restricts its promising applications in high-performance white LEDs and wide-gamut displays. Herein, we develop a structural rigidity-enhancing strategy using a novel KHF₂:Mn⁴⁺ precursor as a Mn source to construct a proton-containing water-resistant phosphor K₂(H)TiF₆:Mn⁴⁺ (KHTFM). The parasitic [HMnF₆]^- complexes in the interstitial site from the fall off the KHF₂:Mn⁴⁺ are also transferred to the K₂TiF₆ host by ion exchange to form KHTFM with rigid bonding networks, improving the water resistance and thermostability of the sample. The KHTFM sample retains at least 92% of the original emission value after 180 min of water immersion, while the non-water-resistant K₂TiF₆:Mn⁴⁺(KTFM) phosphor maintains only 23%. Therefore, these findings not only illustrate the effect of protons on fluoride but also provide a novel insight into commercial water-resistant fluoride phosphors.

Green thin film for stable electrical switching in a low-cost washable memory device: proof of concept

Low-cost and washable resistive switching (RS) memory devices with stable retention and low operational voltage are important for higher speed and denser non-volatile memories. In the case of green electronics, pectin has emerged as a suitable alternative to toxic metal oxides for resistive switching applications. Herein, a pectin-based thin film was fabricated on a fluorine-doped tin oxide glass substrate for RS mechanism. The presence of sp3-C groups with low binding energy corresponds to tunable charged defects and the oxygen vacancies confirmed by the O 1s spectra that plays a decisive role in the resistive switching mechanism, as revealed by X-ray photoemission spectroscopy (XPS). The surface morphology of the pectin film shows homogeneous growth and negligible surface roughness (38.98 ± 9.09). The pectin film can dissolve in DI water (10 minutes) owing to its ionization of carboxylic groups, that meet the trends of transient electronics. The developed Ag/pectin/FTO-based memory cell exhibits stable and reproducible bipolar resistive switching behavior along with an excellent ON/OFF ratio (104) and negligible electrical degradation was observed over 30 repeated cycles. Hence, it appears to be a valuable application for green electronics. Indeed, biocompatible storage devices derived from natural pectin are promising for high-density safe applications for information storage systems, flexible electronics, and green electronics.

A Reverse Strategy to Restore the Moisture-deteriorated Luminescence Properties and Improve the Humidity Resistance of Mn4+ -doped Fluoride Phosphors

Fluoride phosphors as red components for warm white LEDs have attracted a tremendous amount of research attention. But these phosphors are extremely sensitive to moisture, which seriously limits their practical industrial applications. To tackle this problem, unlike all the straightforward preventive strategies, a reverse strategy "Good comes from bad" was successfully developed to treat the degraded K₂ SiF₆  : Mn⁴⁺ (D-KSFM) phosphor in the present study, which not only completely restores the luminescence properties, but also significantly enhances the moisture resistance at the same time. After treatment with an oxalic acid solution as restoration modifier, the emission intensity of the D-KSFM phosphor can be restored to 103.7% of the original K₂ SiF₆  : Mn⁴⁺ red phosphor (O-KSFM), and the moisture resistance is remarkably improved. The restored K₂ SiF₆  : Mn⁴⁺ (R-KSFM) maintains approximately 62.3% of its initial relative emission intensity after immersing in deionized water for 300 min, while the reference commercial K₂ SiF₆  : Mn⁴⁺ with a protective coating (C-KSFM) is only 33.2%. As a proof of general applicability, this strategy was also conducted to K₂ TiF₆  : Mn⁴⁺ phosphor, which is less moisture-stable than K₂ SiF₆  : Mn⁴⁺ . The luminescence intensity of the degraded K₂ TiF₆  : Mn⁴⁺ (D-KTFM) phosphor can be restored to 162.6% of original level of the K₂ TiF₆  : Mn⁴⁺ synthesized through a cation exchange approach without any treatment (O-KTFM). The emission intensity of the restored K₂ TiF₆  : Mn⁴⁺ (R-KTFM) phosphor retains 62.8% of its initial emission intensity after soaking in deionized water for 300 min. Finally, the R-KSFM phosphors were packaged into white light-emitting diodes with blue InGaN chips and Y₃ Al₅ O₁₂  : Ce³⁺ yellow phosphors. The WLEDs display excellent color rendition with higher color rendering index, lower color temperature (WLED-II: R_a =83.6, R₉ =57.3, 3743 K, η_l =199.68 lm/W; WLED-III: R_a =90.4, R₉ =94.2, 2892 K, η_l =183.3 1 m/W). The above results show that the reverse strategy can be applied in those phosphor materials with poor moisture resistance to restore luminescence properties and improve moisture resistance without excessively care about the deterioration during the production, storage and transportation.

Dual-Shelled RbLi(Li3 SiO4 )2 :Eu2+ @Al2 O3 @ODTMS Phosphor as a Stable Green Emitter for High-Power LED Backlights

The stability of luminescent materials is a key factor for the practical application in white light-emitting diodes (LEDs). Poor chemical stability of narrow-band green-emitting RbLi(Li₃ SiO₄ )₂ :Eu²⁺ (RLSO:Eu²⁺ ) phosphor hinders their further commercialization even if they have excellent stability against thermal quenching. Herein, we propose an efficient protection scheme by combining the surface coating of amorphous Al₂ O₃ and hydrophobic modification by octadecyltrimethoxysilane (ODTMS) to construct the moisture-resistant dual-shelled RLSO:Eu²⁺ @Al₂ O₃ @ODTMS composite. The growth mechanisms of both the Al₂ O₃ inorganic layer and the silane organic layer on the phosphor surface are investigated. The results remarkably improve the water-stability of this narrow-band green emitter. The evaluation of the white LED by employing this composite as the green component demonstrates that RLSO:Eu²⁺ @Al₂ O₃ @ODTMS is a promising candidate for the high-performance display backlights, and this dual-shelled strategy provides an alternative method to improve the moisture-resistant property of humidity-sensitive phosphors.

Bifunctional Passivation Strategy to Achieve Stable CsPbBr3 Nanocrystals with Drastically Reduced Thermal-Quenching

The thermal quenching behavior (temperature-dependent luminescence) has severely hindered the practical applications of CsPbX₃ nanocrystals. Here, we find that a simple surface treatment using ammonium hexafluorosilicate (AHFS, (NH₄)₂SiF₆) can drastically reduce the thermal quenching of CsPbBr₃ nanocrystals (CPB-NCs) while enhancing their photostability. The AHFS-treated sample sustains 90% of its original emission intensity as the temperature rises to 353 K, which is much better than that (17%) of the pristine sample. Meanwhile, the thermally stable AHFS-treated sample could maintain 93% of its initial PL emission after a 450 nm LED illumination of 53 h. Structural and surface characterizations indicate that the hydrolyzable AHFS absorbed on the surface could lead to a bifunctional passivation for CPB-NCs, through fluoride ions and its hydrolyzed product of silica, which can reduce the thermal quenching by limiting thermally activated carriers trapping into vacancies and block the attack from external environmental factors.

Local structure modulation of Mn4+-doped Na2Si1−yGeyF6 red phosphors for enhancement of emission intensity, moisture resistance, thermal stability and application in warm pc-WLEDs

Mn⁴⁺-doped Na₂Si_1−yGe_yF₆ red phosphors with efficient water and thermal stabilities were synthesized for high-performance warm pc-WLEDs.

Optimizing and adjusting the photoluminescence of Mn4+-doped fluoride phosphors via forming composite particles

Nowadays, Mn⁴⁺-doped red phosphors are widely used in white LEDs to improve the color rendering index and decrease the correlated color temperature.

Integrated Surface Modification to Enhance the Luminescence Properties of K2TiF6:Mn4+ Phosphor and Its Application in White-Light-Emitting Diodes

Narrow-band Mn⁴⁺-doped fluoride phosphors have become a research hotspot worldwide. In this study, we propose integrated surface modification processes to enhance the performance and stability of the luminescence properties of K₂TiF₆:Mn⁴⁺ (KTF) phosphor. These integrated process are applied in the initial synthesis step, coating of the as-synthesized powder post-treatment process, and during the application of the phosphor in the white-light-emitting diode (WLED) device. Surface etching is conducted to remove impurities and small particles in KTF. Double-shell coating forms a stable protective layer outside the KTF. Atomic layer deposition is employed for the surface of the WLED device.

Highly Stable K2SiF6:Mn4+@K2SiF6 Composite Phosphor with Narrow Red Emission for White LEDs

Poor water resistance and nongreen synthesis remain great challenges for commercial narrow red-emitting phosphor A₂MF₆:Mn⁴⁺ (A = alkali metal ion; M = Si, Ge, Ti) for solid-state lighting and display. We develop here a simple and green growth route to synthesize homogeneous red-emitting composite phosphor K₂SiF₆:Mn⁴⁺@K₂SiF₆ (KSFM@KSF) with excellent water resistance and high efficiency without the usage of toxic and volatile hydrogen fluoride solution. After immersing into water for 6 h, the as-obtained water-resistant products maintain 76% of the original emission intensity, whereas the emission intensity of non-water-resistant ones steeply drops down to 11%. A remarkable result is that after having kept at 85% humidity and at 85 °C for 504 h (21 days), the emission intensity of the as-obtained water-resistant products is at 80-90%, from its initial value, which is 2-3 times higher than 30-40% for the non-water-resistant products. The surface deactivation-enabled growth mechanism for these phosphors was proposed and investigated in detail. We found that nontoxic H₃PO₄/H₂O₂ aqueous solution promotes the releasing and decomposition of the surface [MnF₆]^2- ions and the transformation of the KSFM surface to KSF, which finally contributes to the homogeneous KSFM@KSF composite structure. This composite structure strategy was also successfully used to treat KSFM phosphor prepared by other methods. We believe that the results obtained in the present paper will open the pathway for the large-scale environmentally friendly synthesis of the excellent antimoisture narrow red-emitting A₂MF₆:Mn⁴⁺ phosphor to be used for white light-emitting diode applications.

Waterproof Narrow-Band Fluoride Red Phosphor K2TiF6:Mn4+ via Facile Superhydrophobic Surface Modification

With unique and efficient narrow-band red emission and broadband blue light absorption characteristics, Mn⁴⁺-activated fluoride red phosphors have gained increasing attention in warm white LEDs (WLEDs) and liquid crystal display (LCD) backlighting applications, whereas the intrinsic hygroscopic nature of these phosphors have inevitably limited their practical applications. Herein, a waterproof narrow-band fluoride phosphor K₂TiF₆:Mn⁴⁺ (KTF) has been demonstrated via a facile superhydrophobic surface-modification strategy. With the use of superhydrophobic surface modification with octadecyltrimethoxysilane (ODTMS) on KTF surfaces, the moisture-resistance performance and thermal stability of the phosphor KTF can be significantly improved. Meanwhile, the absorption, and quantum efficiency did not show obvious changes. The surface-modification processes and mechanism, as well as moisture-resistance performances and luminescence properties, of the phosphors have been carefully investigated. It was found that the luminous efficiency (LE) of the modified KTF was maintained at 83.9% or 84.3% after being dispersed in water for 2 h or aged at high temperature (85 °C) and high humidity (85%) atmosphere (HTHH) for 240 h, respectively. The WLEDs fabricated with modified KTF phosphor showed excellent color rendition with lower color temperature (2736 K), higher color rendering index (CRI, Ra = 87.3, R9 = 80.6), and high luminous efficiency (LE = 100.6 lm/W) at 300 mA. These results indicate that hydrophobic silane coupling agent (SCA) surface modification was a promising strategy for enhancing moisture resistance of humidity-sensitive phosphors, exhibiting great potential for practical applications.

A new reductive dl-mandelic acid loading approach for moisture-stable Mn4+ doped fluorides

Different from traditional coating procedures, a novel reducing reagent loading approach for moisture-stable Mn⁴⁺ doped fluorides is introduced.

Luminescence properties and warm white LED application of a ternary-alkaline fluoride red phosphor K2NaAlF6:Mn4+

Electroluminescence spectra and a photograph of a LED device featuring K₂NaAlF₆:Mn⁴⁺under 20 mA drive current as well as a CIE chromaticity diagram for the WLED.