Blue Light Excitation Research Articles

An efficient LiSrGaF6:Cr3+ fluoride phosphor with broadband NIR emission towards sunlight-like full-spectrum lighting.

Sunlight-like full-spectrum phosphor-converted light-emitting diodes (pc-LEDs) require near-infrared (NIR) emission bands to fill the spectrum gap and consequently propel their widespread applications. Although fluoride NIR phosphors have been increasingly investigated, balancing high quantum efficiency (QE), high thermal stability, and wideband NIR emission to obtain excellent overall performance in a single system is still a challenge for Cr3+-doped fluoride NIR phosphor and is significant for direct utilization. Herein, a high-efficiency and thermally stable broadband NIR emission was realized in a novel LiSrGaF6:Cr3+ fluoride phosphor benefitting from a relatively weak crystal field and electron-phonon coupling effect. Upon blue light excitation, the ultra-broad NIR luminescence ranging from 650 to 1150 nm can be achieved with an FWHM of 149 nm peaking at ∼813 nm. Furthermore, this system possesses a high QE of up to 76.88% and its emission intensity at 423 K still maintains 61.62% of its initial intensity at room temperature. An NIR output power of 42.82 mW and photoelectric conversion efficiency of 14.27% of NIR pc-LED devices have also been presented based on this NIR phosphor, demonstrating its possible application in compact nonvisible light sources. In addition, a highly continuous sunlight-like vis-NIR pc-LED was further constructed by employing a blue chip with commercial cyan (BaSi2O2N2:Eu2+), yellow (Y3Al5O12:Ce3+), red (CaAlSiN3:Eu2+), and this LiSrGaF6:Cr3+ NIR phosphor. The as-obtained pc-LED exhibits an ultra-broad spectrum ranging from 400 nm to 1000 nm, exhibiting a higher color reproduction with a color rendering index (CRI) of 95.1 and luminous efficiency (LE) of 50.22 lm W-1. These results indicate that LiSrGaF6:Cr3+ phosphor can be a promising NIR phosphor candidate for high-quality sunlight-like full-spectrum lighting and infrared night vision technology.

Blue-light-excitable pure and efficient short-wave infrared luminescenceviaCr3+→ Yb3+energy transfer in a KYbP2O7:Cr3+phosphor

A novel KYbP2O7:Cr3+inorganic phosphor that emits pure and efficient SWIR photoluminescence upon blue light excitation has been developed, and can be used as a stable luminescence converter for a SWIR emitter.

Insights into blue-light activated red-emitting persistent luminescence from Pr3+-doped phosphors.

In recent years, a series of persistent luminescence materials excitable by blue light have been developed and widely used in many fields such as optical information storage, AC-LEDs, anti-counterfeiting and bio-imaging. However, it is still a long-standing challenge to develop a superior red-emitting persistent phosphor that can be efficiently excited by blue light. In this work, a novel blue-light excited red-emitting persistent phosphor CaCd2Ga2Ge3O12:Pr3+ was successfully synthesized by using a solid-state method, showing excellent luminescence properties. Moreover, the phase purity, crystal structure, photoluminescence spectra, afterglow emission spectra, and three-dimensional thermoluminescence spectrum were successfully investigated. Under 294 nm excitation, photoluminescence spectra show a single orange emission and a series of peaks centered at 492, 537, 568, 614 and 664 nm, which correspond to the 3P0 → 3H4, 3P0 → 3H5, 3P2 → 3H6, 1D2 → 3H4, and 3P0 → 3F2 transitions of Pr3+, respectively. Interestingly, after blue light excitation, the afterglow luminescence exhibits red long emission, which is attributed to the 1D2 → 3H4 transition of Pr3+. Through thermoluminescence spectra and three-dimensional thermoluminescence spectra, we analyze the reasons for the different colors of photoluminescence and afterglow luminescence. The results imply that there are two types of traps, and the depth of shallow traps and deep traps is calculated to be 0.684 and 0.776 eV, respectively. It is worth noting that the photoluminescence is attributed to the 4f2 → 4f5d and f → f transitions of Pr3+, and the afterglow luminescence is ascribed to a tunneling-related process and the transition of electrons from the valence band to the conduction band. The obtained red-emitting persistent phosphors provide a promising pathway toward AC-LEDs, multi-cycle bio-imaging and other fields.

A high-performance metal halide perovskite-based laser-driven display.

Laser-driven liquid crystal displays (LCDs) comprising metal halide perovskites (MHPs) as the blue-to-green/red color converters are at the forefront of ongoing intense research on the development and improvement of display devices. However, the inferior high photoluminescence quantum yield (PLQY) of MHPs under the excitation of high-power blue light and photoluminescence deterioration at high temperatures remain major concerns. Herein, we design a kind of octylamine-modified MHP via binding energy engineering, and the synthesized materials show PLQY of 97.6% under the excitation of a blue laser at 450 nm. Meanwhile, this design endows a structural self-healing ability to achieve a high PLQY and luminescence stability under high temperature (90 °C) and high flux excitation (386 mW cm-2). The blue light-excitable MHPs with a near unity PLQY, strong stability, and low PLQY deterioration are further encapsulated into a laser-driven LCD device. This prototype demonstrates excellent color gamut (132% NTSC, 98% Rec. 2020), illuminance intensity (>10 000 lux), and energy consumption (47.5% of commercial consumption), and hence is expected to be beneficial for the reduction of energy consumption in backlight display devices, particularly in large-screen outdoor displays.

Highly Efficient Narrow‐Band Green Emission in LaZn1‐xMnxAl11O19 Magnetoplumbite Phosphors toward White LED Application and Optical Thermometer

AbstractMn2+‐doped phosphors with narrow‐band green emission are promising for white light‐emitting diodes (WLEDs) to achieve high color rendering index and efficacy. Here, a series of narrow‐band green‐emitting LaZn1−xMnxAl11O19 (0.01 ≤ x ≤ 0.30) magnetoplumbite phosphors (λem = 515 nm) with full width at half maximum (FWHM) of ≈26 nm are designed based on highly symmetrical crystallographic structure. These green phosphors exhibit good photoluminescence quantum yield (PLQY) and small thermal quenching (TQ) performance (86%@423 K) under 450 nm blue light excitation. By further heavy doping Mn2+ into LaZnAl11O19, a broadband red emission peaking at ≈672–697 nm appears upon blue light excitation due to the Mn2+–Mn2+ super‐exchange interactions. A dual‐wavelength emission in LaZn1−xMnxAl11O19 (0.5 ≤ x ≤ 1.0) phosphors provides thermal‐sensitive emission for ratiometric temperature sensing with good relative sensitivity. Benefitting from the Eu2+ → Mn2+ energy transfer, the green emission from Mn2+ is increased by 26 times, and the internal QY of La0.97Zn1−xMnxAl11O19:0.03Eu2+ reaches as high as 88% upon 350 nm light excitation. The efficient blue‐to‐green phosphors are obtained and used as candidates for violet‐excited WLEDs. This study has a guiding role in the development of Mn2+‐doped phosphors in mineral structure with photoluminescence control based on high symmetry and Mn2+–Mn2+ dimers.

Mn4+ activated dodec-fluoride red phosphor Na3Li3In2F12:Mn4+ with excellent waterproof stability for WLEDs

Mn4+ activated fluoride red phosphors, as candidate red materials in white light-emitting diodes (WLEDs), have received widespread attention. However, the poor water stability limits their application. Herein, a novel dodec-fluoride red phosphor Na3Li3In2F12:Mn4+ with good waterproof stability was successfully synthesized by solvothermal method. The crystal structure, optical property, micro-morphology, element composition, waterproof property and thermal behavior of Na3Li3In2F12:Mn4+ phosphor were analyzed. Under the 468 nm blue light excitation, the Na3Li3In2F12:Mn4+ phosphor has narrow emission bands in the area of 590–680 nm. Compared with commercial red phosphor K2SiF6:Mn4+, the Na3Li3In2F12:Mn4+ phosphor possesses better waterproof stability. When soaked in water for 360 min, the PL intensity of the Na3Li3In2F12:Mn4+ phosphor remains at initial 80%. Finally, warm WLEDs with CRI of 87 and CCT of 3386 K have been fabricated using blue InGaN chip, YAG:Ce3+ yellow phosphor and Na3Li3In2F12:Mn4+ red phosphor.

Broadband photodetection using one-step CVD-fabricated MoS2/MoO2 microflower/microfiber heterostructures

Molybdenum disulfide (MoS2) has been combined so far with other photodetecting semiconductors as an enhancing agent owing to its optical and electronic properties. Existing approaches demonstrated MoS2-incorporated photodetector devices using complex and costly fabrication processes. Here, we report on simplified one-step on the chemical vapor deposition (CVD) based synthesis of a unique microfiber/microflower MoS2-based heterostructure formed by capturing MoO2 intermediate material during the CVD process. This particular morphology engenders a material chemical and electronic interplay exalting the heterostructure absorption up to ~ 98% over a large spectral range between 200 and 1500 nm. An arsenal of characterization methods were used to elucidate the properties of these novel heterostructures including Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectrometry, high-resolution transmission and scanning electron microscopies, and Kelvin probe force microscopy. Our findings revealed that the MoS2 and the MoO2 crystallize in the hexagonal and monoclinic lattices, respectively. The integration of the MoS2/MoO2 heterostructures into functional photodetectors revealed a strong photoresponse under both standard sun illumination AM1.5G and blue light excitation at 450 nm. Responsivity and detectivity values as high as 0.75 mA W−1 and 1.45 × 107 Jones, respectively, were obtained with the lowest light intensity of 20 mW cm−2 at only 1 V bias. These results demonstrate the high performances achieved by the unique MoS2/MoO2 heterostructure for broadband light harvesting and pave the way for their adoption in photodetection applications.

Luminescence properties and spectral modulation of the ultra-broadband, highly efficient near-infrared luminescent material CaGa4O7:Cr3+, Cr4+, Yb3+

Recently, near-infrared phosphors have received a lot of attention due to their wide application in the field of detection and analysis, and it is urgent to develop efficient broadband NIR phosphors. In this paper, a conventional high-temperature solid-phase method was used to prepare a novel near-infrared phosphor CaGa4O7:Cr3+, Cr4+, which provides two emission bands ranging from 600 to 1000 nm and 1100–1600 nm. Although there are only four and five coordination sites in the CaGa4O7 (CGO) lattice, the doping of the Cr3+ ions in the CGO causes the Ga–O tetrahedral distortion into an octahedron, providing a favorable environment for the emission of the Cr3+ ions. Under blue light excitation, Cr3+ emits luminescence in the NIR I region from 600 to 1000 nm with a half-height width of up to 148 nm. With increasing Cr ion concentration, more and more Cr4+ preferentially occupy the four coordinated Ga3+ sites, and the intensity of the ultra-broad emission band in the NIR II region (1100 nm–1600 nm) increases with a full width at half maximum (FWHM) of 262 nm. To further optimize the emission spectrum, Yb3+ was codoped into CGO: Cr3+, Cr4+, the energy transfers from Cr3+ to Yb3+ in CGO was found, thus filling the gap between 1000 and 1100 nm in the CGO emission spectrum and obtaining a more complete ultra-wide spectrum. Moreover, the luminescence mechanism, energy transfer efficiency, and quantum yield are also studied in detail, and the ability of CaGa4O7:Cr3+, Cr4+, and Yb3+ luminescent materials to achieve ultra-broadband efficient near-infrared emission was demonstrated.

Spark plasma sintering of MgAl2O4:Mn2+ transparent ceramic phosphors with low thermal quenching, narrow-band green emission.

MgAl2O4:Mn2+ transparent ceramics were fabricated by reactive spark plasma sintering (SPS). The ceramic samples show narrow-band green emission under the 450 nm blue light excitation, which is corresponding to 4T1(4 G)-6A1(6S) transition of Mn2+ in the tetrahedral site. The emission peak of the Mg0.93Al2O4:0.07Mn2+ ceramic sample was located at 525 nm with the full-width at half-maximum (FWHM) value of 36 nm. The internal quantum yield (IQY) of Mg0.93Al2O4:0.07Mn2+ reached 63%. The emission intensity remained ∼98% at 150 °C compared to its initial value at room temperature, showing excellent thermal quenching performance. The results indicated that MgAl2O4:Mn2+ ceramic phosphor is a promising candidate for high brightness, wide gamut display backlight applications.

Simultaneous Absorption and Near‐Infrared Emission Enhancement of Cr3+ Ions in MgGa2O4 Spinel Oxide via Anionic F‐Substitution

AbstractNear‐infrared (NIR) phosphor‐converted light‐emitting diodes (pc‐LEDs) are newly emerging broadband NIR light sources. However, the lack of high‐performance NIR‐emitting materials limits their popularization. Herein, an anionic F‐substitution strategy is presented to regulate the light absorption and emission of MgGa2O4:Cr3+ phosphors. Accordingly, absorption enhancement as well as emission redshift and broadening are achieved for F‐substituted MgGa2O4:Cr3+ (MGOF:Cr3+) phosphors, simultaneously with high efficiency and excellent thermal stability. Upon blue light excitation, the MGOF:0.02Cr3+ phosphor exhibits a broadband NIR emission (650–1200 nm) with a peak wavelength (λmax) of 835 nm and a full width at half maximum of ≈250 nm. Furthermore, MGOF:0.02Cr3+ has a near‐unity internal quantum efficiency and its emission intensity at 150 °C maintains 94% of the initial value. A record external quantum efficiency of 60.6% is further achieved for MGOF:0.08Cr3+ with a redshifted λmax of 870 nm. The Cr3+ local structural alteration with F‐substitution is revealed to account for the outstanding NIR luminescence characteristics of MGOF:Cr3+ in view of systematic structural characterization and spectroscopic analysis. A broadband NIR pc‐LED device with good optical performance is fabricated and its application in semiconductor wafer inspection is demonstrated. This study initiates a new way to design high‐performance NIR phosphors.

Rose bengal-mediated photoinduced atom transfer radical polymerization for high sensitivity detection of target DNA

Convenient and sensitive detection of biomolecules is of utmost importance in the field of early disease screening. In this study, a Rose Bengal-Mediated photoinduced atom transfer radical polymerization (photoATRP) method was used to achieve highly sensitive detection of target DNA (tDNA). The tDNA was specifically recognized using PNA with terminal modified sulfhydryl groups, and the initiator α-bromophenylacetic acid (BPAA) was attached to the electrode surface via a phosphate-Zr4+-carboxylate acid structure. Under the excitation of blue light, rose bengal (RB) acts as a photocatalyst, β-nicotinamide adenine dinucleotide (NADH) as an electron donor, and ferrocenylmethyl methacrylate (FMMA) as a monomer to activate the photoATRP reaction and generate a large number of electroactive polymer chains on the electrode surface. Under optimal conditions, the method can be used for the quantitative analysis of tDNA in the concentration range of 1–105 fM (R2 = 0.994) with a limit of detection (LOD) of 0.115 fM. This metal-free mediated photoATRP biosensor, with low cost and environmental friendliness, has great potential in the field of highly sensitive biomolecule detection.

Fundus autofluorescence pattern in different cases of cone inherited macular dystrophies

AbstractPurpose: To study fundus autofluorescence (FAF) with blue light excitation (488 nm) in different cases of cone inherited macular dystrophies an to assess differential characteristics.Methods: We studied different cone inherited retinal dystrophies due primary to ABCA4 mutation with blue FAF and correlate the findings with the clinical impairment. We compared with the findings in other mutations.Results: We presented 9 cases of Stargardt diseases with ABCA4 mutation with different blue FAF characteristics, from single macular impairment with an hypofluorescence, pattern, hyperreflective flecks around the central lesion or flecks extended outside the vascular branches. The extension of the flecks was no correlate with the degree of functional impairment. We compared with other cone dystrophies such as CRX mutation, with similar findings than the ones with only central impairment. Asymptomatic CRX mutation showed a hyperreflective central lesion.Conclusions: FAF is an essential tool to diagnose and follow‐up inherited retinal dystrophies with primary macular manifestation. Same mutation and clinical stage could present different patterns.

Effective Blue Light-Absorbing AuAg Nanoparticles in InP Quantum Dots-Based Color Conversion.

In typical color-by-blue mode-based quantum dot (QD) display devices, only part of the blue excitation light is absorbed by QD emitters, thus it is accompanied by the leakage of blue light through the devices. To address this issue, we offer, for the first time, the applicability of AuAg alloy nanoparticles (NPs) as effective blue light absorbers in InP QD-based color-by-blue platforms. For this, high-quality fluorescent green and red InP QDs with a double shell scheme of ZnSe/ZnS were synthesized and embedded in a transparent polymer film. Separately, a series of Au/Ag ratio-varied AuAg NPs with tunable plasmonic absorption peaks were synthesized. Among them, AuAg NPs possessing the most appropriate absorption peak with respect to spectral overlap with blue emission are chosen for the subsequent preparation of AuAg NP polymeric films with varied NP concentrations. A stack of AuAg NP polymeric film on top of InP QD film is then placed remotely on a blue light-emitting diode, successfully resulting in systematically progressive suppression of blue light leakage with increasing AuAg NP concentration. Furthermore, the beneficial function of the AuAg NP polymeric overlayer in mitigating undesirable QD excitation upon exposure to ambient lights was further examined.

A novel red-emitting Na5W3O9F5:Eu3+ phosphor with high color purity for blue-based WLEDs

Red phosphor plays a key role in improving the lighting and display quality of phosphor-converted white light-emitting diodes (pc-WLEDs). Meanwhile, developing new luminescent matrix materials can positively contribute to the acquisition of ideal and efficient phosphors. In this work, we propose a novel red-emitting Na5W3O9F5:Eu3+ (NWOF:Eu3+) phosphor. The phase composition, morphology, electronic structure and photoluminescence properties of the NWOF:Eu3+ phosphor were systematically investigated. The EXAFS results prove that the Eu3+ dopants occupy the Na2 and Na3 sites in the NWOF host. Under 466 nm blue light excitation, NWOF:xEu3+ (0.05 ≤ x ≤ 0.25) phosphors display a dominant red emission at 607 nm and achieves a high color purity (97.44%) due to the dominant electric dipole transition (5D0→7F2) of Eu3+ ions. Impressively, this red-emitting NWOF:0.25Eu3+ phosphor exhibits relatively superior thermal stability (450 K, >50%) and excellent chromaticity stability (2.32 × 10−4 ≤ ΔE ≤ 6.23 × 10−3) from 298 K to 498 K. The activation energy for thermal quenching effect is determined to be 0.22 eV. Moreover, the pc-WLED was fabricated by coupling a 460 nm blue chip with the as-synthesized NWOF:0.25Eu3+ red phosphor and commercial YAG:Ce3+ phosphor. The optical parameters of the as-fabricated pc-WLED are also measured, and the CIE coordinates remain almost constant as the drive current increases from 20 mA to 120 mA. These results indicate that the NWOF:0.25Eu3+ red phosphors should be a suitable candidate as a red component for the preparation of pc-WLEDs.

Luminescent properties of a double-perovskite Rb2KScF6:Mn4+ red-emitting phosphor for white light-emitting diodes

Searching for efficient Mn4+ red phosphors for white lighting and display backlighting has drawn great attention. In this work, an efficient Mn4+-doped fluoroscandate, Rb2KScF6:Mn4+, with short fluorescence lifetime is prepared via a facile co-precipitation method. It was found that the nonequivalent occupation of Mn4+ for Sc3+ leads to the identifications of sharp red emissions, enhanced zero-phonon line, high quantum efficiency and short fluorescence lifetime upon blue light excitation. Thanks to the luminescent properties, good optical parameters of high color rendering index, low correlated color temperature, and acceptable color gamut were achieved by coating the red Rb2KScF6:Mn4+ phosphor with yellow Y3Al5O12:Ce3+ or green β-SiAlON:Eu2+ phosphor in various white light-emitting diodes, demonstrating its potential role for white light illumination and backlight display applications.

Mn2+ doped BaAl11O16N phosphors with narrow band green emission and superior thermal stability for backlighting display applications

Here, BaAl11O16N: Mn2+ green phosphor was synthesized by a two-step high-temperature solid-phase method, and its phase structure, morphology and photoluminescence properties were studied in detail. The phosphor has a wide excitation range of 240–500 nm, and the most effective excitation bands are in the blue spectral regions, indicating that BaAl11O16N: Mn2+ green phosphor can be effectively excited by the commercial blue LED chip. Under the excitation of ultraviolet and blue light, the BaAl11O16N: Mn2+ phosphor shows bright green light emission, with a peak of 514 nm and a half peak width of about 31 nm. The emission properties with temperature change show that the BaAl11O16N: Mn2+ phosphor has good thermal stability and excellent color stability. The white light-emitting diode (a blue InGaN chip combined with BaAl11O16N: 0.25Mn2+ phosphor and a commercial K2SiF6: Mn4+ phosphor) exhibits a NTSC value of 119.3%. Therefore, it can be concluded that the BaAl11O16N: Mn2+ phosphor the ideal choice for wide color gamut backlight as a potential efficient phosphor with green narrow-band emission.

Blue Light-Excitable Broadband Yellow Emission in a Zero-Dimensional Hybrid Bismuth Halide with Type-II Band Alignment

Zero-dimensional (0D) organic-inorganic hybrid metal halides have captured broad interest in the lighting and display fields because of their unique electronic structures and splendid broadband emission properties. However, the blue light-excitable broadband yellow emissions have been rarely reported in 0D hybrid metal halides. Here, we design a new 0D bismuth hybrid, (4cmpyH)2BiCl5 (1, 4cmpy = 4-(chloromethyl)pyridine), featuring isolated edge-sharing bioctahedral [Bi2Cl10]4- dimers surrounded by rigid, conjugated, and luminescent organic [4cmpyH]+ cations. This material is able to show intrinsic broadband yellow emissions under blue light (468 nm) excitation with a long lifetime of 22.33 μs and a photoluminescence (PL) quantum yield of 5.56%. Solid-state UV-vis spectroscopy studies prove that introducing organic π-conjugated groups into hybrid systems leads to absorption in the visible light region, in favor of photoexcitation by visible light. By comparing the PL data of 1 and the organic template at room temperature and measuring variable-temperature PL spectra of 1, the blue light-excited broadband emission of 1 can be attributed to the synergistic emissions of intramolecular π → π* and n → π* transitions in the organic cations and triple self-trapped exciton (STE) states centralized at the highly distorted Bi-Cl lattices. Moreover, density functional theory calculations reveal a type-II band alignment in 1 with an indirect band gap of 2.64 eV, which is together determined by organic cations and inorganic bioctahedral units. To the best of our knowledge, our work represents the first report on the blue light-excitable STE emission in 0D Bi-based metal halides, which will largely promote the rapid development of novel high-performance yellow light-emitting materials.

Photoinduced Carbene for Effective Photodynamic Therapy Against Hypoxic Cancer Cells

Photoinduced Carbene for Effective Photodynamic Therapy Against Hypoxic Cancer Cells

Ultra-broadband near-infrared Gd3MgScGa2SiO12: Cr, Yb phosphors: Photoluminescence properties and LED applications

Developing novel broadband near-infrared (NIR) phosphors is crucial to promote NIR phosphor-converted light emitting diodes (pc-LEDs) development. In this work, a new ultra-broadband NIR phosphor Gd 3 MgScGa 2 SiO 12 : Cr 3+ (GMSGS) was achieved by replacing Sc 3+ -Ga 3+ in Gd 3 Sc 2 Ga 3 O 12 with Mg 2+ -Si 4+ . Under the excitation of blue light, the peak emission wavelength of GMSGS: 0.04Cr 3+ is about 820 nm with a full width at half maximum (FWHM) of ∼180 nm and an internal quantum efficiency (IQE) of 50 %. Benefited from the superposition of Cr 3+ emission and highly efficient Yb 3+ emission excited by energy transfer (ET) from Cr 3+ , the codoped GMSGS: 0.04Cr 3+ , 0.007Yb 3+ phosphor shows an ultra-broadband of 300 nm. Moreover, Yb 3+ -codoping improves the thermal stability due to the ET from Cr 3+ to more thermally stable Yb 3+ emitters, and the integrated intensity of GMSGS: 0.04Cr 3+ , 0.007Yb 3+ at 400 K was 63 % of that at room temperature. The packaging results exhibit that ~20 mW output power was achieved at 100 mA input current, which suggests promising potential of GMSGS: Cr 3+ , Yb 3+ phosphor in NIR pc-LED applications. • A novel broadband NIR garnet phosphor Gd 3 MgScGa 2 SiO 12 :Cr 3+ is developed. • The phosphor shows broadband NIR emissions in 700–1100 nm (λ max = 820 nm). • The phosphor exhibits high quantum yield (~50 %) and good thermal stability. • An ultra-broadband GMSGS: Cr 3+ , Yb 3+ phosphor was achieved owing to the energy transfer from Cr 3+ to Yb 3+ . • The NIR phosphor-converted LED with the NIR output power with ~20 mW at 100 mA drive current is achieved.

Variable luminnescence chromaticity and energy transfer in CaZnOS: Pr3+, Mn2+ by ultraviolet and blue excitations

Pr3+ and Mn2+ co-doped CaZnOS phosphors are prepared by high-temperature solid state reaction method and the photoluminescence property is investigated systematically. Under 283 ​nm ultraviolet and 447 ​nm blue light excitations, green emission from CaZnOS, Pr3+ and red emission from Mn2+ are obtained and the emission color is modulated from green to yellow and red by adjusting the ratio of Pr3+ to Mn2+ concentration. The photoluminescence process under 283 ​nm and 447 ​nm excitations are dependent on energy transfer from CaZnOS to Pr3+ and Mn2+, as well as energy transfer from Pr3+ to Mn2+. The energy transfer mechanism between Pr3+ and Mn2+ is confirmed to be dipole-quadrupole interaction. Particularly, under 447 ​nm blue excitation, CaZnOS: 1%Pr3+, 3%Mn2+ exhibits bright yellow emission with chromaticity coordinates of (0.372, 0.428) and quantum yields of 46.37%, implying a potential application in blue-chip excited white light emitting diodes (W-LEDs).