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1. Dual-site occupancy induced broadband cyan emission in Ba ₂ CaB ₂ Si ₄ O ₁₄ :Ce ³⁺

   https://doi.org/10.1039/D0TC02625E  

   You, Shihai; Zhuo, Ya; Chen, Qiulin; Brgoch, Jakoah; Xie, Rong-Jun (November 2020, Journal of Materials Chemistry C)

   null (Ed.)

   There is a significant need to identify cyan-emitting phosphors capable of filling the “cyan-gap” (480–520 nm) in full-visible-spectrum phosphor-converted white light-emitting diodes (pc-wLEDs). Here, a new broadband cyan-emitting phosphor that enables addressing of this challenge is reported. The compound, Ba 2 CaB 2 Si 4 O 14 :Ce 3+ , presents a bright cyan emission peaking at 478 nm with a large full width at half maximum of 142 nm (6053 cm −1 ), and minimal thermal quenching. The photoluminescence properties originate from Ce 3+ residing at two different crystallographic sites, a [BaO 9 ] distorted elongated square pyramid and a [CaO 6 ] trigonal prism. This combination results in an efficient, broad emission covering the blue to green region of the visible spectrum. Fabricating a simple dichromatic ultraviolet ( λ ex = 370 nm) pumped pc-wLED using Ba 2 CaB 2 Si 4 O 14 :Ce 3+ along with a commercially available red phosphor demonstrates full-visible-spectrum white light with high color rendering index ( R a > 90) and tunable correlated color temperature, showing the potential of this material for achieving high-quality LED-based lighting. 

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2. A comparative study of europium doped phosphor materials for white light generation

   https://doi.org/10.1117/12.3040940  

   Palmer-Tesema, Yannik; Reddy, Bommareddi Rami (March 2025, SPIE)

   Digonnet, Michel J; Jiang, Shibin (Ed.)

   Nowadays there is a great demand for LED bulbs which are replacing incandescent light bulbs. LED bulbs are compact, rugged, and free from pollution. Diodes emit a single wavelength. However, phosphor coated diodes generate white light on exposure to blue or violet light. Global research is ongoing to design phosphor coatings which emit high intensity in a broad spectral wavelength region. We are also investigating different phosphor materials to address this issue. We are investigating the suitability of europium doped crystals and glasses for this purpose. Crystals used for this study were procured from commercial sources and the glasses were made in our laboratory by the melt quenching technique. The glass samples were then polished with sandpapers of different grades. Detailed spectroscopy measurements were performed to characterize the materials. Absorption spectral measurements of the materials were performed using a Cary 3E spectrophotometer. Emission was stimulated from the samples by exposing them to blue or violet diode lasers. A compact spectrometer was used for fluorescence spectral measurements. Emission spectral data and lifetime measurements were used for unambiguous spectroscopic assignments. From the emission spectral measurements, color coordinates and color temperature were derived. 

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3. Advancing Human-Centric LED Lighting Using Na₂MgPO₄F:Eu²⁺

   https://doi.org/10.1021/acsami.1c00909  

   Hariyani, Shruti; Brgoch, Jakoah (March 2021, ACS Applied Materials & Interfaces)

   null (Ed.)

   The proliferation of energy-efficient light-emitting diode (LED) lighting has resulted in continued exposure to blue light, which has been linked to cataract formation, circadian disruption, and mood disorders. Blue light can be readily minimized in pursuit of “human-centric” lighting using a violet LED chip (λem ≈ 405 nm) downconverted by red, green, and blue-emitting phosphors. However, few phosphors efficiently convert violet light to blue light. This work reports a new phosphor that meets this demand. Na2MgPO4F:Eu2+ can be excited by a violet LED yielding an efficient, bright blue emission. The material also shows zero thermal quenching and has outstanding chromatic stability. The chemical robustness of the phosphor was also confirmed through prolonged exposure to water and high temperatures. A prototype device using a 405 nm LED, Na2MgPO4F:Eu2+, and a green and red-emitting phosphor produces a warm white light with a higher color rendering index than a commercially purchased LED light bulb while significantly reducing the blue component. These results demonstrate the capability of Na2MgPO4F:Eu2+ as a next-generation phosphor capable of advancing human-centric lighting. 

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4. Full-Color InGaN/AlGaN Nanowire Micro Light-Emitting Diodes Grown by Molecular Beam Epitaxy: A Promising Candidate for Next Generation Micro Displays

   https://doi.org/10.3390/mi10080492  

   Bui, Ha Quoc; Velpula, Ravi Teja; Jain, Barsha; Aref, Omar Hamed; Nguyen, Hoang-Duy; Lenka, Trupti Ranjan; Nguyen, Hieu Pham (August 2019, Micromachines)

   We have demonstrated full-color and white-color micro light-emitting diodes (μLEDs) using InGaN/AlGaN core-shell nanowire heterostructures, grown on silicon substrate by molecular beam epitaxy. InGaN/AlGaN core-shell nanowire μLED arrays were fabricated with their wavelengths tunable from blue to red by controlling the indium composition in the device active regions. Moreover, our fabricated phosphor-free white-color μLEDs demonstrate strong and highly stable white-light emission with high color rendering index of ~ 94. The μLEDs are in circular shapes with the diameter varying from 30 to 100 μm. Such high-performance μLEDs are perfectly suitable for the next generation of high-resolution micro-display applications. 

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5. Near Unity PLQY and High Stability of Barium Thiocyanate Based All-Inorganic Perovskites and Their Applications in White Light-Emitting Diodes

   https://doi.org/10.3390/photonics8060209  

   Adhikari, Gopi Chandra; Thapa, Saroj; Yue, Yang; Zhu, Hongyang; Zhu, Peifen (June 2021, Photonics)

   All-inorganic lead halide perovskite (CsPbX3) nanocrystals (NCs) have emerged as a highly promising new generation of light emitters due to their extraordinary photophysical properties. However, the performance of these semiconducting NCs is undermined due to the inherent toxicity of lead and long-term environmental stability. Here, we report the addition of B-site cation and X-site anion (pseudo-halide) concurrently using Ba(SCN)2 (≤50%) in CsPbX3 NCs to reduce the lead and improve the photophysical properties and stability. The as-grown particles demonstrated an analogous structure with an almost identical lattice constant and a fluctuation of particle size without altering the morphology of particles. Photoluminescence quantum yield is enhanced up to near unity (~98%) by taking advantage of concomitant doping at the B- and X-site of the structure. Benefitted from the defect reductions and stronger bonding interaction between Pb2+ and SCN− ions, Ba(SCN)2-based NCs exhibit improved stability towards air and moisture compared to the host NCs. The doped NCs retain higher PLQY (as high as seven times) compared to the host NCs) when stored in an ambient atmosphere for more than 176 days. A novel 3D-printed multiplex color conversion layer was used to fabricate a white light-emitting diode (LED). The obtained white light shows a correlated color temperature of 6764 K, a color rendering index of 87, and luminous efficacy of radiation of 333 lm/W. In summary, this work proposes a facile route to treat sensitive lead halide perovskite NCs and to fabricate LEDs by using a low-cost large-scale 3-D printing method, which would serve as a foundation for fabricating high-quality optoelectronic devices for near future lighting technologies. 

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