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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. Local environment rigidity and the evolution of optical properties in the green-emitting phosphor Ba _1−x Sr _x ScO ₂ F:Eu ²⁺

   https://doi.org/10.1039/D1TC05411B  

   Hariyani, Shruti; Amachraa, Mahdi; Khan, Mariam; Ong, Shyue Ping; Brgoch, Jakoah (February 2022, Journal of Materials Chemistry C)

   Developing chemically and thermally stable, highly efficient green-emitting inorganic phosphors is a significant challenge in solid-state lighting. One accessible pathway for achieving green emission is by forming a solid solution with superior blue-emitting materials. In this work, we demonstrate that the cyan-emission ( λ em = 481 nm) of the BaScO 2 F:Eu 2+ perovskite can be red-shifted by forming a solid solution following (Ba 1− x Sr x ) 0.98 Eu 0.02 ScO 2 F ( x = 0, 0.075, 0.15, 0.25, 0.33, 0.40). Although green emission is achieved ( λ em = 516 nm) as desired, the thermal quenching (TQ) resistance is reduced, and the photoluminescence quantum yield (PLQY) drops by 65%. Computation reveals the source of these changes. Surprisingly, a basic density functional theory analysis shows the gradual Sr Ba substitution has negligible effects on the band gap ( E g ) energy, suggesting the activation energy barrier for the thermal ionization quenching remains unchanged, while the nearly constant Debye temperature indicates no loss of average structural rigidity to explain the decrease in the PLQY. Instead, temperature-dependent ab initio molecular dynamics (AIMD) simulations show that gradual changes of the Eu 2+ ion's local coordination environment rigidity are responsible for the drop in the observed TQ and PLQY. These results express the need to computationally analyze the local rare-earth environment as a function of temperature to understand the fundamental origin of optical properties in new inorganic phosphors. 

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3. Optical properties of undoped, Eu ³⁺ doped and Li ⁺ co-doped Y ₂ Hf ₂ O ₇ nanoparticles and polymer nanocomposite films

   https://doi.org/10.1039/c9qi01181a  

   Gupta, Santosh K.; Zuniga, Jose P.; Abdou, Maya; Ghosh, P. S.; Mao, Yuanbing (January 2020, Inorganic Chemistry Frontiers)

   Desirable phosphors for lighting, scintillation and composite films must have good light absorption properties, high concentration quenching, high quantum efficiency, a narrow color emission, and so forth. In this work, we first show that undoped yttrium hafnate Y 2 Hf 2 O 7 (YHO) nanoparticles (NPs) display dual blue and red bands after excitation using 330 nm light. Based on density functional theory (DFT) calculations, these two emission bands are correlated with the defect states arising in the band-gap region of YHO owing to the presence of neutral and charged oxygen defects. Once doped with Eu 3+ ions (YHOE), the YHO NPs show a bright red emission, a long excited state lifetime and stable color coordinates upon near-UV and X-ray excitation. Concentration quenching is active when Eu 3+ doping reaches 10 mol% with a critical distance of ∼4.43 Å. This phenomenon indicates a high Eu 3+ solubility within the YHO host and the absence of Eu 3+ clusters. More importantly, the optical performance of the YHOE NPs has been further improved by lithium co-doping. The origin of the emission, structural stability, and role of Li + -co-doping are explored both experimentally and theoretically. DFT calculation results demonstrate that Li + -co-doping increases the covalent character of the Eu 3+ –O 2− bonding in the EuO 8 polyhedra. Furthermore, the YHOE NPs have been dispersed into polyvinyl alcohol (PVA) to make transparent nanocomposite films, which show strong red emission under excitation at 270 and 393 nm. Overall, we demonstrate that the YHO NPs with Eu 3+ and (Eu 3+ /Li + ) doping have a high emission intensity and quantum efficiency under UV and X-ray excitation, which makes them suitable for use as phosphors, scintillators and transparent films for lighting, imaging and detection applications. 

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4. Combining experiment and computation to elucidate the optical properties of Ce ³⁺ in Ba ₅ Si ₈ O ₂₁

   https://doi.org/10.1039/c9cp05576b  

   Zhong, Jiyou; Hariyani, Shruti; Zhuo, Ya; Zhao, Weiren; Liu, Xiang; Wen, Jun; Brgoch, Jakoah (January 2020, Physical Chemistry Chemical Physics)

   Complex alkaline earth silicates have been extensively studied as rare-earth substituted phosphor hosts for use in solid-state lighting. One of the biggest challenges facing the development of new phosphors is understanding the relationship between the observed optical properties and the crystal structure. Fortunately, recent improvements in characterization techniques combined with advances in computational methodologies provide the research tools necessary to conduct a comprehensive analysis of these systems. In this work, a new Ce 3+ substituted phosphor is developed using Ba 5 Si 8 O 21 as the host crystal structure. The compound is evaluated using a combination of experimental and computational methods and shows Ba 5 Si 8 O 21 :Ce 3+ adopts a monoclinic crystal structure that was confirmed through Rietveld refinement of high-resolution synchrotron powder X-ray diffraction data. Photoluminescence spectroscopy reveals a broad-band blue emission centered at ∼440 nm with an absolute quantum yield of ∼45% under ultraviolet light excitation ( λ ex = 340 nm). This phosphor also shows a minimal chromaticity-drift but with moderate thermal quenching of the emission peak at elevated temperatures. The modest optical response of this phase is believed to stem from a combination of intrinsic structural complexity and the formation of defects because of the aliovalent rare-earth substitution. Finally, computational modeling provides essential insight into the site preference and energy level distribution of Ce 3+ in this compound. These results highlight the importance of using experiment and computation in tandem to interpret the relationship between observed optical properties and the crystal structures of all rare-earth substituted complex phosphors. 

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5. From Model to Material: Machine Learning Enabled Discovery of LED‐Compatible Phosphors

   https://doi.org/10.1002/adom.202502034  

   Lee, Nakyung; Brgoch, Jakoah (January 2026, Advanced Optical Materials)

   Abstract Phosphor‐converted white light‐emitting diodes are transforming energy‐efficient lighting technologies. At the core of their performance are Ce³⁺and Eu²⁺activated phosphors, whose photoluminescent properties significantly impact the lighting devices’ efficiency and, equally important, govern the light quality. However, the discovery of new phosphors that meet the stringent requirements needed for commercialization has remained a challenge. Recent advances in data‐driven approaches, particularly machine learning and optimization algorithms, have begun to accelerate this process. These methods enable the accurate prediction of key photoluminescent properties and facilitate the exploration of vast compositional spaces of inorganic phosphors, guiding the targeted synthesis of new high‐performance phosphors. This review highlights the major progress in data‐driven discovery of Ce³⁺and Eu²⁺phosphors, emphasizing property prediction, materials screening, and experimental validation. It concludes with an outlook on future opportunities and challenges in the application of artificial intelligence to phosphor discovery. 

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