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1. 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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2. 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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3. Tunable Dual‐Band White Light Emission from Gua ₃ CuCl ₄ and Gua ₇ Cu ₃ X ₁₀ ·3DMF (X = Br, I)

   https://doi.org/10.1002/adpr.202200172  

   Gilley, Isaiah_W; Creason, Tielyr_D; McWhorter, Timothy_M; Saparov, Bayram (August 2022, Advanced Photonics Research)

   All‐inorganic copper(I) halides have recently emerged as attractive alternatives to lead‐based halide perovskites and rare‐earth‐doped inorganics for light emission applications. Most of the newly discovered all‐inorganic Cu(I) halides demonstrate high‐efficiency blue emission albeit with unusually poor tunability of photoluminescence (PL) properties. This work reports the facile preparation of three new copper(I) halides based on the guanidinium cation: (CN₃H₆)₃CuCl₄, (CN₃H₆)₇Cu₃Br₁₀·3(C₃H₇NO), and (CN₃H₆)₇Cu₃I₁₀·3(C₃H₇NO). A comprehensive characterization of PL is presented for these novel materials, which have highly tunable, dual blue–yellow emission responsive to both excitation wavelength and vacuum annealing. These have remarkable photoluminescence quantum yield (PLQY) values of up to 34.6% and color‐rendering indices (CRI) up to 97% for tunable, single‐phase white light emission with correlated color temperatures (CCT) ranging from 4851 to 18 921 K, demonstrating the excellent potential of Cu(I) halides for light emission applications. 

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4. Dual functions of CO ₂ molecular activation and 4f levels as electron transport bridges in erbium single atom composite photocatalysts therefore enhancing visible-light photoactivities

   https://doi.org/10.1039/D1TA02926F  

   Chen, Qiuyu; Gao, Guoyang; Zhang, Yanzhou; li, Yini; Zhu, Hongyang; Zhu, Peifen; Qu, Yang; Wang, Guofeng; Qin, Weiping (July 2021, Journal of Materials Chemistry A)

   Only when the interfacial charge separation is enhanced and the CO 2 activation is improved, can the heterojunction nanocomposite photocatalyst be brought into full play for the CO 2 reduction reaction (CO 2 RR). Here, Er 3+ single atom composite photocatalysts were successfully constructed based on both the special role of Er 3+ single atoms and the special advantages of the SrTiO 3 :Er 3+ /g-C 3 N 4 heterojunction in the field of photocatalysis for the first time. As we expected, the SrTiO 3 :Er 3+ /g-C 3 N 4 (22.35 and 16.90 μmol g −1 h −1 for CO and CH 4 ) exhibits about 5 times enhancement in visible-light photocatalytic activity compared to pure g-C 3 N 4 (4.60 and 3.40 μmol g −1 h −1 for CO and CH 4 ). In particular, the photocatalytic performance of SrTiO 3 :Er 3+ /g-C 3 N 4 is more than three times higher than that of SrTiO 3 /g-C 3 N 4 . From Er 3+ fluorescence quenching measurements, photoelectrochemical studies, transient PL studies and DFT calculations, it is verified that a small fraction of surface doping of Er 3+ formed Er single-atoms on SrTiO 3 building an energy transfer bridge between the interface of SrTiO 3 and g-C 3 N 4 , resulting in enhanced interfacial charge separation. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM) and adsorption energy calculations demonstrated that the exposed Er single-atoms outside the interface on SrTiO 3 preferentially activate the adsorbed CO 2 , leading to the high photoactivity for the CO 2 RR. A novel enhanced photocatalytic mechanism was proposed, in which Er single-atoms play dual roles of an energy transfer bridge and activating CO 2 to promote charge separation. This provides new insights and feasible routes to develop highly efficient photocatalytic materials by engineering rare-earth single-atom doping. 

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5. 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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