Warm White Light-emitting Diodes Research Articles

A Novel Broadband Green Phosphor La2W2O9: Bi3+, and Its Application in High Color-Rendering Index pc-WLED

Broadband green phosphors have important applications in overcoming the blue-green (cyan) 470–510[Formula: see text]nm gap of phosphor-converted white LED (pc-WLED) and achieving high color rendering index (CRI) white lighting. In this work, a broadband green phosphor La2W2O9: [Formula: see text]Bi[Formula: see text] was synthesized by solid-state method. The phase, morphology and luminescence properties of the series of phosphors were systematically studied. The results showed the La2W2O9: [Formula: see text]Bi[Formula: see text] green phosphor exhibits a wide emission band in the range of 400–800[Formula: see text]nm with full width at half-maximum (FWHM) of 164[Formula: see text]nm, filling the cyan gap and reaching its peak at 550[Formula: see text]nm. The phosphor exhibits broadband excitation, and the excitation range covers the wavelength region of 200–500[Formula: see text]nm, and matches well with commercial ultraviolet LED. With the obtained broadband green phosphor, commercial CaAlSiN3:Eu[Formula: see text] red phosphor, commercial BaMgAl[Formula: see text]O17:Eu[Formula: see text] blue phosphor, and a 365[Formula: see text]nm commercial chip, a warm white pc-WLED device with a high color-rendering index (Ra[Formula: see text]97.4, R1–R15[Formula: see text]90) and low correlated color temperature (CCT[Formula: see text]3610[Formula: see text]K) was fabricated. The results demonstrate the wide range of applications for La2W2O9:Bi[Formula: see text] phosphor in the field of premium warm white LED lighting.

Red-shift of the photoluminescent emission and enhancement of the internal quantum efficiency by co-doping Gd3+ in Tb3Al5O12: Ce3+ phosphors for warm WLEDs

White Light Emitting Diodes (WLEDs) are widely used in our lives as the fourth generation of solid-state lighting sources. However, the phosphors in the WLEDs device lack a red component, resulting in a cool white light, which affects the quality of lighting while damaging the user's eyesight. In this work, the Tb3Al5O12: Ce3+ (TAG: Ce3+) and Tb3Al5O12: Ce3+, Gd3+ (TAG: Ce3+, Gd3+) phosphors were synthesized by sol-gel method. Powder X-ray diffraction analysis confirmed the successful substitution of Ce3+ and Gd3+ in the system, as evidenced by the quantifiable expansion of the unit cell volume when Tb3+ was replaced with Ce3+ and Gd3+. As the increasing of Gd3+ doping concentration in the TAG: 0.025Ce3+, yGd3+ phosphors, the emission peak of Ce3+ (arises from the 5d→4f transition) shifted from 565 nm to 580 nm. The photoluminescence emission intensity of TAG: 0.025Ce3+, 0.6Gd3+ phosphor can be increased by about 192% compared to TAG: 0.025Ce3+ phosphor (y = 0). The Gd3+-to-Ce3+ energy transfer is robustly supported by the prolonged lifetime of Ce3+ with an increase in Gd3+ content in TAG: 0.025Ce3+, yGd3+. Notably, the energy transfer process from Gd3+ to Ce3+ effectively enhanced the internal quantum efficiency (IQE) of the TAG: 0.025Ce3+, yGd3+ phosphors, up to 70.14%. Variable-temperature emission spectra indicates that TAG: Ce3+, Gd3+ phosphors prepared by the sol-gel method have excellent luminescent thermal stability. Ultimately, the WLEDs devices assembled with TAG: Ce3+, Gd3+ phosphors can produce warm white light, which indicates that TAG: Ce3+, Gd3+ phosphors are a potential material for warm WLEDs.

Designing a high-efficiency broadband cyan phosphor for low-blue full-spectrum LED lighting

Efficient cyan-emitting phosphor plays an important role in the development of solid-state lighting, which is indispensable to filling the cyan gap for full-spectrum warm-white light-emitting diodes (WLEDs) with high color rendering index (CRI). Herein, a novel highly efficient broadband cyan phosphor Ce3+-doped Ca3HfAl2Si2O12 (CHASO: Ce3+) garnet compound was developed by the substitution of Lu3+-Al3+ with Ca2+-Hf4+/Si4+ in Lu3Al5O12. The crystal structure and photoluminescence (PL) properties of CHASO: Ce3+ were investigated in detail. Notably, CHASO: Ce3+ phosphor can be effectively excited by violet light (390 – 430 nm) and exhibited bright cyan emissions around 490 nm with high PL internal quantum yields of 89.2 %. Moreover, the integrated PL intensity of the phosphor at 423 K was 66.3 % of that at room temperature. Finally, by incorporating CHASO: 11 %Ce3+ with commercial blue/yellow/red phosphor onto a violet LED chip (400 nm), the prototype full-spectrum WLEDs device exhibits warm white light with high color rendering index (CRI, Ra and R9 > 90) and low correlated color temperature 3301 K. These results suggest the highly efficient phosphor CHASO: Ce3+ is promising for low-blue full-spectrum healthy lighting.

Sm3+ activated Ba3LaNa(PO4)3F fluorophosphate phosphor: Synthesis, characterization and their photoluminescence investigation for warm WLEDs

In this present research report, the series of Ba3LaNa(PO4)3Fphosphor doped with Sm3+ was successfully synthesized by using a high-temperature solid-state reaction method. The phase purity was examined using X-ray diffraction (XRD), which confirmed a pure phase of prepared material after sintering the sample at 700 °C. Fourier transform infrared (FT-IR) spectra showed absorption bands corresponding to the stretching and vibrational modes of PO4 in phosphate. Scanning electron microscopy (SEM) images displayed the morphology of sample and agglomerated structure of micron-sized particles. Photoluminescence excitation (PLE) and emission spectra of the Ba3LaNa(PO4)3F: Sm3+ phosphors were studied. When excited with near-UV light, the phosphor showed three prominent peaks at 567, 604, and 643 nm. The emission spectra for different concentrations of Sm3+ ions were also measured to find the optimal dopant concentration. The highest intensity was observed at a 2.0 mol% concentration of Sm3+ ions at 604 nmwith concentration quenching occurring beyond this point. The CIE chromaticity coordinates for the different concentration phosphor were located in the orange-red region, indicating its characteristic light emission. So therefore, these results suggested that the synthesized reddish-orange light-emitting Ba3LaNa(PO4)3F: Sm3+prepared phosphor is promising for applications in white light-emitting diodes (WLEDs).

A samarium (Ⅲ)-activated tantalum-based double perovskite phosphor with high thermostability

Inorganic double perovskite phosphor materials have received much attention in solid-state lighting domain due to efficient and versatile luminescence colors. This study employs a high-temperature solid-phase method to synthesize a series of Sm3+-activated Sr2YTaO6 (SYTO):Sm3+ phosphors with double perovskite structure. The structure, morphology, and content/temperature-dependent orange-red emissions are thoroughly elucidated. For SYTO:3 mol%Sm3+, the luminescence intensity at 423 K remains 95 % of that at 298 K, verifying high thermostability. Meanwhile, the phosphor exhibits good resistance to color shifting. A high Sm3+ content induces luminescence quenching due to dipole–dipole interaction. Finally, the synthesized material is utilized to fabricate a satisfactory and warm white light-emitting diode.

Rational Synthesis of Single-Component White-Light-Emitting Carbon Nanodots for Warm White LEDs with a High Color Rendering Index of 95.4

Rational Synthesis of Single-Component White-Light-Emitting Carbon Nanodots for Warm White LEDs with a High Color Rendering Index of 95.4

High-efficiency RbASiF6:Mn4+ (A = K, Cs) phosphors obtained by one-step green synthesis method

Red-emitting Mn4+-doped fluoride phosphors are recognized as promising materials for high-performance warm white light-emitting diodes (WLEDs). However, the extensive use of toxic hydrofluoric acid in traditional synthesis methods hinders their development and commercialization. Furthermore, the traditional solid-phase method often has cumbersome sintering steps, high temperature, long holding time, and certain safety hazards, so it is very necessary to develop a green synthesis method with simple steps and low energy consumption. In this study, a low-temperature solid-state method is proposed to synthesize RbASiF6:Mn4+ (A = K, Cs) phosphors by one step. Optimal emission intensities were observed at Mn4+ concentrations of 1.2 % in RbKSiF6 and 2.1 % in RbCsSiF6. These phosphors demonstrated high thermal stability. At 423 K, the photoluminescence intensities of RbKSiF6:1.2 %Mn4+ and RbCsSiF6:2.1 %Mn4+ reached 114 % and 87 % of their respective values at room temperature. Meanwhile, the chromaticity shifts were almost negligible, and high color purity was achieved for both phosphors. The electro-optical performance of WLED devices utilizing these phosphors, in combination with YAG:Ce3+ and GaN chips, showed high color rendering indices (CRI) and low correlated color temperatures (CCT) across varying currents. Specifically, under a driving current of 20 mA, the device incorporating RbKSiF6:1.2 %Mn4+ exhibited a CRI of 94 and a CCT of 3732 K, with a luminous efficacy of 61 lm/W. These findings highlight the potential of green-synthesized RASFM phosphors in advancing the application of warm WLEDs.

Er3+ activated BaLaGaO4 multifunctional green phosphors for optical thermometers and WLEDs

Er3+-doped BaLaGaO4 green phosphors was synthesized through a high-temperature solid-state reaction technique. The phase structure and morphology test results of the phosphor indicate that the BaLaGaO4 material was successfully synthesized and Er3+ ions were successfully doped into the main lattice. This doping does change the basic structure of the crystal. BaLaGaO4:Er3+ phosphor exhibits bright green emission centered at 545 nm when excited by 381 nm ultraviolet light or 980 nm near-infrared light. The optimal doping concentration is found to be x = 0.04. To quantify the temperature sensitivity of the phosphor, the fluorescence intensity ratio method was used. Within the temperature range of 298–473 K, the maximum relative sensitivities are 1.35%/K (298 K, 381 nm) and 1.45%/K (298 K, 980 nm), respectively. The maximum absolute sensitivities are 0.67%/K (473 K, 381 nm) and 0.69%/K (473 K, 980 nm), respectively. Finally, white light-emitting diodes (WLEDs) with a high colour index of Ra = 82 and a relatively low correlated colour temperature of CCT = 5064 K are obtained by integrating the synthesized BaLaGaO4:0.04Er3+ green phosphor into warm WLEDs devices. These results suggest that Er3+-activated BaLaGaO4 multifunctional phosphors hold considerable promise in the areas of optical temperature sensing and WLEDs phosphor conversion.

A new zero-dimensional hybrid antimony halide of (C25H46N)2SbCl5 with dual-emission and high quantum-efficiency for light-emitting application

Zero-dimensional (0D) organic-inorganic hybrid metal halides (OIHMHs) have received extensive attention due to their excellent photoelectric properties. Herein, a new 0D OIHMH single crystal, (C25H46N)2SbCl5, has been synthesized by slow antisolvent diffusion. In this crystal structure, C25H46N+ (C25H46N+ = Cetyldimethylbenzylammonium cations) cations separated SbCl52− to form a 0D square pyramid structure. (C25H46N)2SbCl5 single crystals (SCs) manifest bright orange-yellow dual-emission bands at 472 and 616 nm, while having a high photoluminescent quantum yield of 97.5 %. The lifetime of high energy (HE) emission and low energy (LE) emission at room temperature is 9.73 ns and 4.61 μs, respectively. Based on lifetime differences and temperature-dependent spectra, the HE emission band is ascribed to singlet self-trapped excitons (STEs), while the LE emission band with a broad full width at half maxima of 136 nm can be attributed to triplet STEs. (C25H46N)2SbCl5 appeared anti-thermal quenching behavior. In accordance with the luminescence characteristics of (C25H46N)2SbCl5, a warm white light-emitting diode device was fabricated with the correlated color temperature of 3410 K, the relevant color coordinate of (0.41, 0.39) and the color rendering index of 95.1, demonstrating (C25H46N)2SbCl5 a promising phosphor for solid-state light-emitting application.

Preparation and Luminescence Properties of Broadband Orange-Emitting Persistent ScBaZn3GaO7:Bi3+ Phosphor.

This article describes a new kind of afterglow material, ScBaZn3GaO7:Bi3+, which was synthesized through a high-temperature solid-phase method. Its crystal structure, photoluminescent characteristics, and afterglow characteristics were studied and analyzed. Upon excitation at 344 nm, ScBaZn3GaO7:Bi3+ exhibits broadband emission with a central wavelength located at 571 nm (fwhm = 172.98 nm). The sample exhibits an internal quantum efficiency of 65.1%. The bright yellow persistent luminescence of the ScBaZn3GaO7:Bi3+ sample was observed after 365 nm irradiation. Thermoluminescence spectroscopy revealed four primary traps within ScBaZn3GaO7:Bi3+, with depths of 0.676, 0.794, 0.882, and 0.972 eV. The traps located at energy levels of 0.676 and 0.794 eV were identified as the key contributors to the sample's afterglow. Finally, the ScBaZn3GaO7:Bi3+ sample was combined with a UV-LED chip to fabricate a high-power warm white-light-emitting diode (WLED) device, indicating the potential application prospect of ScBaZn3GaO7:Bi3+ phosphor in single-phase warm WLEDs.

A phosphor-in-glass film prepared with a novel orange Lu2GdMg2AlSi2O12:Ce3+ phosphor and a cyan BaSi2O2N2:Eu2+ phosphor

The preparation of phosphor-in-glass (PiG) films containing orange and cyan phosphors is one of the possible ways to improve the color rendering index (CRI) and correlated color temperature (CCT) of white LEDs packaged with PiG films. Recently, by matrix ion substitution, we have synthesized a novel orange Lu2GdMg2AlSi2O12:Ce3+ phosphor. Then, we used a “coating and low-temperature sintering” method to prepare PiG films containing this novel orange phosphor and the commercial cyan BaSi2O2N2:Eu2+ phosphor on sapphire substrates. Combining these PiG films with blue LED chips, warm white LEDs with CRI above 90 and CCT below 4000 K can be obtained. This suggests that the PiG films containing cyan and orange phosphors are promising to improve the CCT and CRI of white LEDs packaged with PiG films.

The preferential orientation controlling for efficient Sb2S3 and low Se content Sb2SeyS3-y indoor photovoltaics

Sb2S3 is a promising absorber material for indoor photovoltaics due to the appropriate direct bandgap of 1.75 eV, high element abundance, low toxicity, stability, and single phase. Considering the indoor lighting irradiance is very low and the resulting carrier numbers are relatively less and Sb2S3 is quasi-one-dimensional crystal structure, the preferential orientation controlling of Sb2S3 is very important to improve the power conversion efficiency (PCE) of Sb2S3 indoor photovoltaics. Herein, Sb2S3 and low Se content Sb2SeyS3-y films are prepared by chemical bath deposition and the preferential orientation of Sb2S3 films is controlled by introducing SbCl3 and selenourea in the growth solution. The uniformity of the S and Se distribution in low Se content Sb2SeyS3-y films is adjusted by introducing EDTA-2Na. Using the warm white LED with a color temperature of 3347 K and illuminance of 1000 lux, Sb2S3 and low Se content Sb2SeyS3-y indoor photovoltaics achieve the PCE of 16.58% for Sb2S3 and 17.62% for Sb2SeyS3-y, which is the highest PCE for antimony chalcogenide indoor photovoltaics. Therefore, the preferential orientation controlling by introducing SbCl3 and selenourea into the growth solution is an efficient strategy for fabricating high-efficiency Sb2S3 and low Se content Sb2SeyS3-y indoor photovoltaics.

Carbon Quantum Dots with Highly Efficient Bandgap Emission for Electroluminescent Light-Emitting Diodes

Carbon quantum dots (CQDs) feature bright and tunable photoluminescence, solution processability, and low toxicity, showing great potential in optoelectronics. The multicolor fluorescent CQDs were first fabricated as active layers in our lab, and then the high-performance electroluminescent warm white light-emitting diodes (LEDs) were obtained with the synthesized bright red CQDs. More significantly, through designing the triangular structure of the carbon core, fluorescent CQDs first achieved the narrow-bandwidth (∼30 nm) electroluminescent LEDs with appreciable stability, high color purity, and high luminescence performance. These results lay the foundation for the development of next-generation high performance displays based on CQDs. Here, we will report the large-scale synthesis of CQDs with near-unity photoluminescence quantum yield and the synthesis of red (625 nm) phosphorescent carbon quantum dot organic frameworks (CDOFs) with a quantum yield of up to 42.3% and realization of high-efficiency red phosphorescent electroluminescent LEDs. The LEDs based on the CDOFs exhibited a red emission with a maximum luminance of 1818 cd m−2 and an EQE of 5.6%. This work explores the possibility of a new perspective for developing high-performance CQD-based electroluminescent LEDs.References Yuxin Shi, Louzhen Fan, et al., Red Phosphorescent Carbon Quantum Dot Organic Framework-Based Electroluminescent Light-Emitting Diodes Exceeding 5% External Quantum Efficiency, Am. Chem. Soc. 2021, 143, 45, 18941–18951Ting Yuan, Louzhen Fan, et al., Carbon Quantum Dots with Near-Unity Quantum Yield Bandgap Emission for Electroluminescent Light-Emitting Diodes, Angew. Chem. Int. Ed. 2023, e202218568.Fanglong Yuan，Louzhen Fan, et al., Engineering triangular carbon quantum dots with unprecedented narrow bandwidth emission for multicolored LEDs, Nat. Commun., 2018, 9, 2249. Figure 1

Synthesis and photoluminescence of Ba1-xSrxMgSi4O10:Eu2+ phosphors for warm white light-emitting-diodes

Efficient and thermally stable blue-cyan-emitting phosphors are urgently demanded to cover the “cyan gap” for high quality light-emitting-diodes (LEDs) lighting. This work provides a series of blue to cyan color-tunable Ba0.96-xSrxMgSi4O10:0.04Eu2+ phosphors developed via solid-solution method. The phase transformation, photoluminescence, quantum efficiency and thermal stability were investigated in detail. Notably, Sr2+ substitution is effective to red-shift the emission toward cyan emission (from 465 to 480 nm). Simultaneously, the quantum efficiency and thermal stability can be well maintained. Finally, using a 365 nm near-ultraviolet (NUV) LED chip combining with the as-prepared blue-cyan-emitting phosphor, β-SiAlON:Eu2+ green-emitting phosphor and CaAlSiN3:Eu2+ red-emitting phosphor, a warm-white LED device was fabricated with correlated color temperature (CCT) of 4329 K, and color-rendering index (CRI) of 92. These results indicate that the Ba1-xSrxMgSi4O10:Eu2+ blue-cyan-emitting phosphors may have potential applications for high quality NUV-pumped warm-white LED lighting.

A novel Na2Ca2Si3O9: Tb3+ glass ceramic with high luminescence efficiency and robust thermal stability for white LED lighting application

Given the increasing demand for white light emitting diode (WLED) lighting devices marked by high color rendering indices (CRI) and exceptional thermal stability, there is a burgeoning interest in developing emitters with enhanced performance. Rare earth (RE) ion-activated glass ceramics (GCs) have garnered significant attention due to their outstanding physicochemical and thermal stability, alongside their high luminescence efficiency. In this study, the GCs doped with Tb3+ ions in the Na2O-CaO-SiO2 system matrix were synthesized, incorporating Na2Ca2Si3O9 nanocrystals averaging less than 100 nm in size. Notably, these GC materials demonstrated superior luminescence efficiency in the green light emission under the irradiation of 376 nm light compared to the parent glass. A comprehensive analysis of fluorescence spectra revealed an impressive internal quantum efficiency of 87.34% for this Tb3+-doped GC. Furthermore, the GC retained 90% and 84% of the initial luminescence intensity at 150°C and 200°C in comparison to the luminescence level at room temperature, showcasing exceptional resistance to fluorescence thermal quenching. Verification experiments utilized UV LED chip, (Sr, Ca)AlSiN3: Eu2+ red phosphor, BaMgAl10O17: Eu2+ blue phosphor, and Tb3+-doped GC to encapsulate the WLED device, achieving a remarkable CRI of 92, CIE chromaticity coordinates (0.3547, 0.3361), and a correlated color temperature (CCT) of 4550K. In conclusion, the experimental outcomes unequivocally underscore the significant application potential of these Tb3+-doped GCs in the territory of warm WLED lighting.

A novel Mn4+-doped Li2Mg4TiO7 red-emitting phosphor for warm white light-emitting diodes

To improve the light quality of warm white-LEDs (w-LEDs), novel Mn4+-activated red-emitting phosphors that can be excited efficiently by blue light with yield high performance are highly imperative. Here, we report a Mn4+-doped Li2Mg4TiO7 (LMT) phosphor prepared via a traditional high-temperature reaction method. The crystal structure and luminescent properties of the LMT:Mn4+ phosphors are studied. An excitation band centered at 470 nm, matches well with the commercial blue LED chips. Upon blue light excitation, a broadband red emssion located at 673 nm due to d-d transitions of Mn4+ is observed. The optimum doping concentration of Mn4+ is determined to be x = 0.08 %. The optimized red-emitting phosphor LMT:Mn4+ attains a photoluminescence quantum yield (PLQY) of 40.0 % and a good thermal resistance (ΔE = 0.43 eV). The combination of the as-obtained red-emitting phosphor, commercially available yellow phosphor, and blue LED chip yields a warm w-LED device, delivering CIE (x, y) = (0.3922, 0.3909), CRI = 70.0 and CCT = 2214 K. Therefore, this work provides a novel LMT:Mn4+ phosphor as a potential red component for warm w-LEDs.

Controllable morphology, excellent stability and non-equivalent doping-induced optical properties of Mn4+-activated K2NaScF6 red phosphor for high-quality warm WLED

Currently, Mn4+ activated fluoride red phosphor has been widely studied to improve the optical performance of white light-emitting diode (WLED) in the field of high-efficiency lighting and wide color gamut backlight display. In this paper, a series of red-emitting K2NaScF6:Mn4+ phosphors are synthesized by a simple co-precipitation method with a non-equivalent substitution of Mn4+ for Sc3+ at room temperature. The crystal structure, morphology and elemental composition of K2NaScF6:Mn4+ phosphors prepared using different reaction conditions are systematically investigated. Interestingly, the K2NaScF6:Mn4+ phosphors exhibit narrowband red emission with low correlated color temperature (CCT), high color purity and short fluorescence lifetime. Compared to equivalent doping, the mechanism of short fluorescence lifetime caused by non-equivalent doping has also been systematically discussed. The optimal doping concentration is determined by setting a series of Mn4+ doping concentrations and the concentration quenching mechanism is analyzed. The crystal field strength (Dq), Racah parameters (B and C) and nephelauxetic ratio (β1) are calculated in detail to evaluate the crystal field environment of Mn4+ in K2NaScF6. The good water resistance of the as-prepared sample K2NaScF6:Mn4+ is verified by comparing with the commercially available phosphor K2SiF6:Mn4+. Moreover, the thermal stability is also analyzed by calculating the activation energy (Ea), chromaticity shift (ΔE) and chromaticity coordinate variation (CCV). Importantly, the as-packaged warm WLED (InGaN chip + YAG:Ce3+ + K2NaScF6:Mn4+) has excellent optical properties (CCT = 4082 K, color rendering index (CRI, Ra = 91.2) and luminous efficiency (LE) = 78.86 lm/W), and it exhibits good output stability at high drive currents. In summary, our work demonstrates that K2NaScF6:Mn4+ red phosphors possess a great potential application in warm WLED for the indoor lighting.

Novel self-activated red-emitting CsSrEu (PO3)6 phosphor: Synthesis, luminescent properties and enhancement by partially anion substitution

Novel self-activated red-emitting CsSrEu(PO3)6 was synthesized by high-temperature solid-phase method, and their enhanced luminescence were obtained by the modification of local structure. CsSrEu(PO3)6 was efficiently excited at 394 nm and emitted bright red light centered around 609 nm. Their luminescence intensity of CsSrEu(PO3)6 phosphor substituted by (BO3)3-/(SiO4)4- is about 1.346 or 1.454 times of the initial values respectively. The temperature-dependent luminescent spectra show that the emission intensity of CsSrEu(PO3)6 substituted by (BO3)3-/(SiO4)4- at 423 K remains 90.9 % and 86.6 % of the initial value respectively. The internal quantum efficiency is 88.4 % and 83.5 % respectively. White light-emitting diode fabricated by the phosphors, commercial blue-green phosphors and 395 nm chips show high color quality. The overall results indicate that the CsSrEu(PO3)6 phosphor substituted by (BO3)3-/(SiO4)4- group is promising candidate in warm white LED and anionic group substitution can be used to optimize luminescent properties of phosphors.

Highly effective red phosphor for warm white LEDs without rare earth elements

The use of red fluorescent powder derived from nitrides and oxides in warm white LEDs is a pressing concern due to its lower quantum efficiency. Fluoride red phosphors activated by Mn4+ ions show promising potential for application in white light-emitting diodes (LEDs) due to their distinctive narrowband red emission and broad blue excitation, along with the relatively mild synthesis conditions required. However, the quantum efficiency of early Mn4+-doped fluoride phosphors was not optimal, highlighting the importance of identifying a suitable preparation method and matrix. Here, we introduce an efficient and thermally stable red fluoride phosphor, Cs2SiF6:Mn4+, which demonstrates a remarkable quantum efficiency of 98.32 % achieved through ion exchange techniques. However, even at a temperature of 423 K, the luminous intensity still maintained at 95 % of that under room temperature conditions. By incorporating Cs2SiF6:Mn4+ as a red emitter, a stable 10 W high-power warm white LEDs with a luminous efficiency of approximately 126.1 lm/W can be realized. These findings underscore the significant potential of the red phosphor Cs2SiF6:Mn4+ in advancing high-performance, high-power warm white LEDs.

Substrate and nutrient manipulation during continuous cultivation of extremophilic algae, Galdieria spp. RTK 37.1, substantially impacts biomass productivity and composition.

The extremophilic nature and metabolic flexibility of Galdieria spp. highlights their potential for biotechnological application. However, limited research into continuous cultivation of Galdieria spp. has slowed progress towards the commercialization of these algae. The objective of this research was to investigate biomass productivity and growth yields during continuous photoautotrophic, mixotrophic and heterotrophic cultivation of Galdieria sp. RTK371; a strain recently isolated from within the Taupō Volcanic Zone in Aotearoa-New Zealand. Results indicate Galdieria sp. RTK371 grows optimally at pH 2.5 under warm white LED illumination. Photosynthetic O2 production was dependent on lighting intensity with a maximal value of (133.5 ± 12.1 nmol O2 mgbiomass -1 h-1) achieved under 100 μmol m-2 s-1 illumination. O2 production rates slowed significantly to 42 ± 1 and <0.01 nmol O2 mgbiomass -1 h-1 during mixotrophic and heterotrophic growth regimes respectively. Stable, long-term chemostat growth of Galdieria sp. RTK371 was achieved during photoautotrophic, mixotrophic and heterotrophic growth regimes. During periods of ammonium limitation, Galdieria sp. RTK371 increased its intracellular carbohydrate content (up to 37% w/w). In contrast, biomass grown in ammonium excess was composed of up to 65% protein (w/w). Results from this study demonstrate that the growth of Galdieria sp. RTK371 can be manipulated during continuous cultivation to obtain desired biomass and product yields over long cultivation periods.