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Article

Optical and Photoconversion Properties of Ce3+-Doped (Ca,Y)3(Mg,Sc)2Si3O12 Films Grown via LPE Method onto YAG and YAG:Ce Substrates

by
Anna Shakhno
1,2,*,
Vitalii Gorbenko
1,
Tetiana Zorenko
1,
Aleksandr Fedorov
3 and
Yuriy Zorenko
1,*
1
Department of Physics, Kazimierz Wielki University in Bydgoszcz, 85-090 Bydgoszcz, Poland
2
Mechantronic Department, Kazimierz Wielki University in Bydgoszcz, 85-074 Bydgoszcz, Poland
3
Institute for Single Crystal, National Academy of Science of Ukraine, Nauky Ave., 60, 61000 Kharkiv, Ukraine
*
Authors to whom correspondence should be addressed.
Materials 2025, 18(15), 3590; https://doi.org/10.3390/ma18153590
Submission received: 17 May 2025 / Revised: 19 July 2025 / Accepted: 28 July 2025 / Published: 30 July 2025
(This article belongs to the Section Materials Physics)
Browse Figures
Versions Notes

Abstract

This work presents a comprehensive study of the structural, luminescent, and photoconversion properties of epitaxial composite phosphor converters based on single crystalline films of Ce3+-activated Ca2−xY1+xMg1+xSc1−xSi3O12:Ce (x = 0–0.25) (CYMSSG:Ce) garnet, grown using the liquid phase epitaxy (LPE) method on single-crystal Y3Al5O12 (YAG) and YAG:Ce substrates. The main goal of this study is to elucidate the structure–composition–property relationships that influence the photoluminescence and photoconversion efficiency of these film–substrate composite converters, aiming to optimize their performance in high-power white light-emitting diode (WLED) applications. Systematic variation in the Y3+/Sc3+/Mg2+ cationic ratios within the garnet structure, combined with the controlled tuning of film thickness (ranging from 19 to 67 µm for CYMSSG:Ce/YAG and 10–22 µm for CYMSSG:Ce/YAG:Ce structures), enabled the precise modulation of their photoconversion properties. Prototypes of phosphor-converted WLEDs (pc-WLEDs) were developed based on these epitaxial structures to assess their performance and investigate how the content and thickness of SCFs affect the colorimetric properties of SCFs and composite converters. Clear trends were observed in the Ce3+ emission peak position, intensity, and color rendering, induced by the Y3+/Sc3+/Mg2+ cation substitution in the film converter, film thickness, and activator concentrations in the substrate and film. These results may be useful for the design of epitaxial phosphor converters with tunable emission spectra based on the epitaxially grown structures of garnet compounds.

1. Introduction

In recent years, the demand for high-efficiency, energy-saving light sources has significantly increased, driven by advancements in lighting and display technology. White light-emitting diodes (WLEDs) have emerged as the dominant choice due to their superior energy efficiency, long lifespan, and environmental benefits, including reduced carbon emissions and lower energy consumption compared to traditional incandescent and fluorescent bulbs [1]. Additionally, WLEDs have found applications beyond general lighting, such as in automotive headlights, backlighting for displays, and even in medical devices, further fueling the need for continuous improvements in their performance and efficiency [2,3].
A critical factor in the overall performance of WLEDs is the phosphor conversion layer, which plays a central role in color rendering and light quality. In most WLED configurations, a blue LED chip is combined with a phosphor material that converts a portion of the blue light into yellow, red, or green light, resulting in a balanced white emission. The efficiency of this conversion process directly impacts the brightness, color rendering index (CRI), and color correlated temperature (CCT) of the emitted light, all of which are crucial parameters for various applications [4,5,6].
The choice of phosphor material is therefore essential in the performance of the device. Among the various phosphor materials available, garnet-based materials doped with rare-earth ions, especially Ce3+, have proven to be among the most effective due to their broad excitation and emission spectra, high quantum efficiency, excellent luminescent properties, and thermal stability under high-power operation [7,8,9]. In particular, the Ce3+-doped Y3Al5O12 (YAG) phosphor is widely used in the industry for producing the high efficiency and good color quality of white light. It is compatible with blue LEDs and offers advantages such as strong absorption in the blue region, stable emission characteristics, and high thermal stability, which is crucial for maintaining performance over long operating hours [10].
The most common pc-WLEDs are produced using the Volume-Casting-Conversion (VCC) design, where a blue LED and powder PC are packed with organic resins [11]. Numerous techniques, including solid-state reactions [12], hydrothermal synthesis [13], coprecipitation [14], spray pyrolysis [15], sol–gel [16], and combustion [17], can be used to make ceramic powder phosphors. The heat generated from the LED chip and PC (Stokes shift and optical losses) cannot be efficiently dissipated because of the poor thermal stability and weak thermal conductivity of the resin (<0.5 W m−1 K−1) [1]. With the increasing demand for high-brightness lighting, the high-power wLEDs and white laser diodes (WLDs) are rapidly developing, and some limitations arise that are associated with the optical, structural, mechanical, and thermal properties of converters. The operating temperature of a color converter can reach even up to 200 °C under high-power LED or laser diode excitation. The extreme heat is generated in the converter, originating from the non-radiative relaxation of phosphors and the heat transfer from high-power LED chips. With the increase in the wLED temperature, color degradation occurs because of the thermal quenching properties of the phosphor, such as luminous decay and color shifting [18]. Furthermore, this setup results in low efficiency because the diffuse phosphor reflects 60% of the total white light back onto the chip [19]. To achieve high efficiency and strong chemical and thermal stability for pc-WLEDs, downconversion phosphors have been developed from powders to plates for the Planar-Chip-Level Conversion (PCLC) approach [20].
In PCLC design, instead of powder, the ceramic, eutectics, or single-crystal phosphors based on the yellow-emitting Ce3+-doped garnets are used for manufacturing high-power WLEDs under blue LED excitation. Nevertheless, glasses and ceramics have a relatively low luminescence efficiency [21], whilst the structure and optical properties of eutectic converters are hard to control. The development of single crystalline (SC) converters is much preferable to ceramics or powders, due to their higher uniformity and internal quantum efficiency (QE) than ceramics or glasses, as well as excellent thermal stability up to 300 °C, and high thermal conductivity (~10 W/(m K) [22,23,24].
It is obvious that the investigation of new types of color converters is an acute problem to be solved with the development of energy-efficient solid-state lighting sources. The minimization trend has focused attention on phosphor films that can be produced using different techniques such as sputtering deposition [25], electrochemical synthesis [26], pulsed laser deposition (PLD) [27], sol–gel [28], metal–organic chemical vapor deposition (MOCVD) [29], and liquid phase epitaxy (LPE) as well [30,31]. Among the presented methods, the LPE technique is a versatile method for the production of SCFs for applications in optoelectronics, with thicknesses in the range of several micrometers up to 200 μm, with excellent material quality and reproducibility [32].
One of the first works in this area was by Kundaliya et al. [32] and Markovskiy et al. [33], who proposed a phosphor converter based on the YAG:Ce and LuAG:Ce garnet phosphor film epitaxially grown onto a YAG substrate, to induce yellow and green emission, respectively. Recently, the possibility of the development of Tb3Al5O12:Ce (TbAG:Ce) single crystalline film converters for wLEDs using the LPE technique was shown [34]. It is especially important to note that, according to the Al2O3-Tb2O3 phase diagram, the Tb3Al5O12 melts incongruently, and it is difficult to grow a high-quality and large-size bulk TbAG:Ce crystal using Czochralski (Cz) or other melt-grown techniques, which is a barrier to its practical applications [35]. However, the single crystalline Tb3Al5O12 matrix or Tb1.3Gd1.5Al5O12 solid solution on their base can be fabricated in the pure garnet phase using low-temperature synthesis methods such as LPE growth [34,36].
The next generation of film converters is the development of a composite color converter (CCC), based on Ce3+-doped film/crystal epitaxial structures [36]. The development of CCCs suggests a few more additional tunable parameters, originating from the single-crystal substrate: (i) Ce3+ doping concentration in the substrate; (ii) thickness of the substrate. Finally, the combination of the emission coming from the Ce3+-doped substrate and the film constituents of the color converter allows for a wide spectrum of WLEDs similar to the spectrum of natural white light to be obtained, with enhanced luminous efficacy in comparison with standard photoconverters.
Phosphors based on the Ce3+-doped mixed {Ca2R}[Sc,B](C,Si2)O12; R = Lu, Y, Gd; B = Sc, Ga, C = Ga, Al silicate garnets can also be used for producing high-power WLEDs with a high color rendering index and low correlated color temperature values [37,38]. Due to the flexibility of the garnet structure, which allows for replacing ions at the dodecahedral { }, octahedral [ ], and tetrahedral ( ) sites, it is possible to replace the host cations and modify the conventional {Y}3[Al]2(Al)3O12 garnet composition for altering the Ce3+ spectroscopic properties to better meet the requirements for utilization in WLEDs. To date, the spectroscopic properties of Ce3+ in some garnets containing Si4+ at tetrahedral sites, namely Y3Mg2AlSi2O12, Y3MgAl3SiO12, CaY2Al4SiO12, MgY2MgAl2Si2O12, CaLu2Al4SiO12, CaLu2Mg2Si3O12, CaY2ZrSc Al3O12:Ce, and Lu1.5Ca1.5Al3.5Si1.5O12:Ce garnets, have been investigated [39,40,41,42,43,44,45,46,47,48,49,50,51].
It has been shown that Ca3Sc2Si3O12:Ce (CSSG) exhibits less thermal quenching of Ce3+ luminescence than YAG:Ce [37,50]. Mixed silicate garnets like Y3+-Mg2+ co-doped CSSG:Ce, e.g., (Ca,Y)3(Mg,Sc)2Si3O12 (CYMSSG), doped with Ce3+ ions, have shown also great potential as powder phosphor materials due to their broader emission spectra and absorption in the blue region than GSSG:Ce, which aligns well with the emission of blue LEDs [51,52]. However, despite the promising properties of these materials, research on the use of CYMSSG:Ce in the single crystalline films (SCF) [53] or crystals [54] as phosphor converters is limited, with even less focus on their performance in composite film–crystal structures based on the silicate garnets [55,56]. This gap hinders a complete understanding of how these materials behave under real LED excitation conditions and how variations in film structure, particularly thickness and variable cation content, influence their photoconversion efficiency.
The present study addresses this gap by investigating the structural, luminescent, and photoconversion properties of epitaxial converters based on Ce3+-doped CYMSSG-based SCFs with varying cation contents. These films were crystallized using the liquid phase epitaxy (LPE) method onto YAG and YAG:Ce single-crystal (SC) substrates, allowing for precise control over the growth process and material properties [18,19,20,21,22,23,24]. By systematically varying the film’s cation composition and thickness, ranging from 19 to 67 µm for Ce3+-doped CYMSSG films on YAG crystals (Series A) and from 10 to 22 µm for those on YAG:Ce crystals (Series B), we thoroughly examined how these parameters influence photoconversion efficiency.
This systematic approach enabled the observation and mapping of distinct trend lines in a chromaticity or color coordinate diagram, clearly illustrating the relationship between film content, thickness, and photoconversion performance. Variations in content and thickness affected key parameters, such as emission spectra and color rendering, which are critical for optimizing the overall luminescence and efficiency of the converter. These trend lines provide valuable insights into the optimal content and film thickness required for enhanced photoconversion, highlighting the importance of precise control over all SCF parameters to achieve the desired optical characteristics in phosphor converters for WLED applications.

2. SCF Growth

Two distinct sets of thin films with nominal compositions of Ce3+-doped Ca2YMgScSi3O12 and Ca1.75Y1.25Mg1.25Sc0.75Si3O12 (Series A and B, respectively), with thicknesses ranging from 10 µm to 67 µm, were fabricated using the LPE method (Table 1). The films were crystallized within a temperature range of 975–990 °C from a supercooled melt solution composed of a PbO:B2O3 flux with a mole ratio of 12:1. The CYMSSG:Ce SCFs were grown on undoped YAG substrates for Series A and on Ce3+-doped YAG substrates for Series B, with orientations close to the (111) crystallographic plane. The YAG and YAG:Ce substrates used in these experiments had a thickness of 0.5 mm. The nominal Ce concentration in the CYMSSG:Ce SCFs and YAG:Ce substrates was approximately 0.05–0.15 at. % and 0.05–0.06 at.%, respectively (Table 1). Further details about the growth process for Ca-Si-based films and the specific mole ratios used for LPE growth can be found in references [57].
The thickness of the SCF samples, denoted as h (in μm), was determined using a weighing method. This approach involved measuring the substrate’s mass before and after the SCF growth cycle with high-precision scales. Film thickness was then calculated using the following formula: h = (m − ms)/(2 × S × ρ), where m is the mass of the substrate with the grown SCF (in grams), ms is the mass of the substrate (in grams), S is the substrate area (in cm2), and ρ is the film density (in g/cm3).
The compositions of single crystals and films were analyzed using a JEOL JSM-820 electron microscope (JEOL Ltd., Akishima, Japan) equipped with an IXRF 500i LN2 Eumex EDX detector (IXRF, Inc., Austin, TX, USA). This advanced tool provided rapid assessments and ensured the precise detection of elemental variations with an accuracy of ±1%. The analysis revealed considerable deviations in the concentrations of Ca, Mg, Sc, and Si cations compared to the nominal (in-melt) formulas (Ca,Y)3(Mg,Sc)2Si3O12 and Ca1.75Y1.25Mg1.25Sc0.75 Si3O12:Ce. Meanwhile, these deviations were consistently less than ±0.2 formula units, as shown in Table 1. Such findings underscore the importance of precise compositional control in material synthesis. To maintain clarity and alignment with experimental results, the study consistently refers to the nominal composition of the SCFs. This approach ensures a standardized comparison while accounting for the slight variations observed during the evaluation process.
The structural quality of Ca2−XY1₊XMg1₊XSc1−XSi3O12:Ce (x = 0–0.25) films grown on YAG substrates was investigated using X-ray diffraction (XRD) with a DRON 4 spectrometer (Saint-Petersburg, former USSR) equipped with a CuKα X-ray source. For this analysis, Samples B1 and B4 with x = 0 and x = 1.25 were chosen, featuring a 0.25 Ce3+ concentration of 0.01 and 0.15 at.% and a thickness of 19 µm and 67 µm, respectively, as illustrated in Figure 1 and Table 1. This sample was selected for its suitability for detailed structural evaluation.
Typically, the single crystallinity of CYMSSG films grown on YAG substrates is confirmed using thinner samples, generally with thicknesses of less than 50–70 µm. This preference is driven by the inherent limitations associated with X-ray diffraction in thicker samples. Specifically, the garnet matrix of CYMSSG films exhibits medium X-ray absorption, which changes the relative intensity of diffraction reflections from the YAG substrate. This effect becomes more pronounced as the film thickness increases, complicating accurate structural characterization in thicker samples (Figure 1).
Therefore, thinner samples are prioritized for initial analysis to reliably confirm single crystallinity. Once verified, the growth process continues to produce thicker films (exceeding 100 µm) for further experimental studies. This sequential approach ensures that the structural integrity and quality of the CYMSSG films are thoroughly assessed before the fabrication of thicker film samples. By addressing the technical constraints of XRD analysis, this method provides a robust framework for characterizing the structural properties of CYMSSG films on YAG substrates, paving the way for their application in advanced optical and photonic systems.
The lattice misfit between the CYMSSG SCFs and the YAG substrate was calculated using the XRD pattern corresponding to the (12 0 0) crystallographic plane of the sample (Figure 1). The standard formula for lattice misfit, expressed as Δa = ((aSCF − asub)/asub) × 100%, was used, where aSCF is the lattice parameter of the film, and asub is the lattice parameter of the YAG substrate. The analysis revealed a lattice mismatch of approximately 2.51–2.57%, which indicates a significant mismatch between the SCF and substrate lattices. Meanwhile, even this degree of mismatch was found to be consistent with high-quality epitaxial growth, where strain and stress at the interface are not yet critical, maintaining the crystalline integrity of the film. This finding is particularly significant as it confirms the successful epitaxial growth of the CYMSSG (x = 0–0.25) film on the YAG substrate.

3. Experimental Technique

To comprehensively investigate the properties of the two sets of thin-film samples (Series A and B) and Ce-doped substrates (Series C), an extensive suite of spectroscopic techniques was employed. These techniques included absorption spectroscopy, photoluminescence (PL) emission, and excitation (PLE) spectroscopy, which together provided a detailed evaluation of the luminescent characteristics of the CYMSSG:Ce SCFs. All spectroscopic measurements were conducted under ambient conditions at room temperature (RT), ensuring their relevance to practical applications.
The absorption spectra of the SCFs were recorded using a Jasco V730 spectrophotometer (Tsukuba, Japan). For a detailed examination of the photoluminescent properties, an FS-5 spectrometer (Edinburgh Instruments, Livingston, UK) was used. Photoconversion spectra were recorded using an AvaSpec-ULS 2048-LTEC fiber-optic spectrophotometer, paired with an AvaSphere-50-IRRAD integrating sphere (Avantes, Apeldoorn, The Netherlands). These measurements enabled a comprehensive analysis of the SCFs’ photoconversion performance, shedding light on their potential for advanced photonic applications. The Osram LBE 6SG (If = 30 mA, V = 2.9 V) blue LED 455 nm (30 mA, 2.9 V) was used as an excitation source to determine the chromaticity parameters of the samples.

4. Absorption and Luminescent Properties

4.1. Absorption Spectra

The absorption spectra of the CYMSSG:Ce SCF/YAG SCFs (Figure 2a) and CYMSSG:Ce SCF/YAG:Ce (Figure 2b) composite samples, as well as the absorption spectra of the YAG:Ce SC substrates (Figure 2c), exhibit distinct features in the 200–500 nm wavelength range, reflecting their optical properties. Notably, broad absorption bands peaking around 341 nm and within the 439–457 nm range, referred to as E2 and E1 bands, respectively, are consistently observed across all analyzed structures, confirming their successful incorporation into the CYMSSG films. These bands are characteristic for the absorption of Ce3+ ions in the garnet host, corresponding to the 4f1(2F5/2)→5d (2E) electronic transitions. Additionally, a spectral feature at 230 nm is attributed to the 4f (2F5/2)→5d1 (T2g) transitions of Ce3+ ions (E3 band). These identifications align with prior studies, which highlight these transitions as key spectral signatures of Ce3+ ions’ presence in garnet matrices [1,2].
Another notable feature of SCF samples is an absorption bands peaked at 300 nm and below 220 nm, corresponding to the 1S0→3P1 and 1P1 electronic transitions of Pb2+ impurity, likely introduced into the film during LPE growth from PbO-based flux. The last Pb2+-related band strongly overlapped with the E3 band of Ce3+ ions. Despite being associated with trace Pb2+ inclusions, this feature provides valuable insights into the real material’s composition and the interactions between dopants and Ce3+ ions [3].
In addition to these primary features, low intensive absorption bands in the UV range, peaking at 370 nm, are evident in the YAG:Ce substrates and absorption spectra of the CYMSSG:Ce SCF/YAG:Ce structure. Generally, such UV bands have been attributed to defect center absorption in garnets, grown or annealed in the reducing atmosphere [58], or containing an excess of Ca2+ ions [53,57], and correspond to the absorption of the F+ center (one charged anion vacancy).
Overall, the analysis of these absorption spectra confirms the effective doping of the SCFs with Ce3+ ions and underscores the impact of trace impurities on their optical behavior.

4.2. PL Spectra

The PL and PLE spectra of samples from Series A and B, as well as substrates from Series C, are shown in Figure 3. The PL spectra of all SCF samples (Figure 3a,b) exhibit intense luminescence characterized by broad emission bands in the green-yellow spectral range. These bands are attributed to the 5d1→4f (2F5/2, 2F7/2) electronic transitions of Ce3+ ions, which are characteristic of the luminescent behavior of cerium-doped garnets. However, it should be noted that Ce3+ emission bands consist of several sub-bands corresponding to non-equivalent Ce3+ multicenters. Specifically, Ce3+ ions replace the dodecahedral positions of Ca2+ and Y3+ cations, which have different local surroundings with Mg2+ and Sc3+ ions in octahedral positions and Si4+ in tetrahedral positions within the garnet lattice. The observed structure of the PL spectra of CYMSSG:Ce SCFs grown on a YAG substrate clearly indicates the presence of multiple Ce3+ emission centers in the CYMSSG host, as described in detail in our previous works [8,18].
The PL spectrum of samples from Series A, which were grown on an undoped YAG substrate, exhibits a broader Ce3+ luminescence band, with two distinct peaks at 510 nm and 548 nm. The slight blue shift in the PL emission and excitation spectra of sample A1 is caused by its lower cerium concentration, which is three times lower than that of the other samples in this set. This blue shift occurs because the reduced Ce3+ concentration limits the energy transfer between different Ce3+ multicenters, primarily affecting those emitting in the longer-wavelength range.
Conversely, the PL spectra of samples from Series B, grown on a Ce3+-doped YAG substrate, display a notably broader emission band with peaks at 536 nm and 573 nm due to the overlap between the PL spectra of the YAG:Ce substrate (Figure 3c) and the CYMSSG:Ce SCFs (Figure 3a). This red shift may also result from variations in the crystal field strength or changes in the covalency of Ce3+–ligand bonds within the Ca2+-Si4+-based CYMSSG host compared to the YAG:Ce substrate [8,18]. Specifically, increased covalency in Ce3+–ligand bonds within the CYMSSG matrix reduces the energy required for Ce3+ electronic transitions, contributing to the observed red shift.
Interactions between Ce3+ ions in YAG:Ce substrates and CYMSSG:Ce films may also lead to energy transfer processes that influence the emission spectra of the epitaxial structure. Understanding these wavelength shifts is crucial for tailoring the material’s properties and optimizing its emission for specific applications. These findings highlight the critical role of the substrate composition in determining the photoluminescence properties of CYMSSG:Ce films. The interactions between SCFs and substrates, particularly those involving cerium doping, significantly impact the energy transfer dynamics and luminescent behavior.

4.3. PLE Spectra

The PLE spectra of Ce3+ ions in YAG:Ce substrates and CYMSSG SCF/YAG and CYMSSG SCF/YAG:Ce structures are presented in Figure 3b,d,f. The 4f (2F5/2)→5d transitions are key characteristics of Ce3+ ion excitation and play a fundamental role in its luminescent behavior. The peak near 456 nm in YAG:Ce substrates is typically associated with the transition from the ground state to the lowest 5d energy level, whereas the 340 nm peak corresponds to a transition to a higher-lying 5d state. These transitions are governed by the symmetry and electronic environment of Ce3+ ions within the garnet matrix. The relative intensities and positions of these bands provide insights into the local crystal field and the energy splitting of the 5d states.
Furthermore, the peaks at 340 nm and 456 nm indicate that the YAG:Ce substrate and its composite structure exhibit efficient absorption capabilities at multiple wavelengths, enabling excitation in both the UV and visible regions. This dual-excitation feature enhances the material’s photoluminescent properties, making it suitable for applications in lighting, displays, and optoelectronic devices.
The PLE spectra for Series A (Figure 3b) exhibit prominent maxima at 346 nm and 454 nm, corresponding to the 4f→5d electronic transitions of Ce3+ ions in the CYMSSG host. These peaks are typical of cerium-doped materials and indicate efficient absorption in the UV and blue regions, making them suitable for excitation by respective LEDs.
The PLE spectra of samples from Series B (Figure 3d) represent a superposition of the PLE spectra of the YAG:Ce substrate and CYMSSG:Ce SCF. These spectra feature a peak at 343 nm (E2) and a broad complex excitation band in the blue region centered at 472 nm (E1). The latter band is a superposition of at least two distinct peaks located at 433 nm and 476 nm. The presence of multiple peaks within the E1 band is typically attributed to the excitation of Ce3+ multicenters in the CYMSSG:Ce film [8,18].
The excitation peak observed at 375 nm in the PLE spectra of Ce3+ luminescence in CYMSSG:Ce SCFs is closely related to intrinsic electronic transitions associated with F+ centers in garnets [1,17]. Specifically, this peak corresponds to the 1A→1B transition of the F+ center, a well-known defect in many crystalline materials, including oxides. The F+ center refers to an oxygen vacancy typically associated with a trapped electron. The presence of this excitation band at 375 nm suggests that F+ centers play a role in the optical behavior of CYMSSG:Ce SCFs, contributing to the material’s overall photonic properties. In particular, the material’s ability to absorb light at this wavelength may influence the efficiency of energy transfer processes and the overall photoluminescent behavior of Ce3+ ions, as interactions between F+ centers and Ce3+ ions can modify emission characteristics.

5. Photoconversion Properties

Prototypes of phosphor-converted white light-emitting diodes (pc-WLEDs) were developed to assess their performance and to investigate how the content and thickness of SCFs affect the colorimetric properties of SCFs and composite converters. These pc-WLEDs were assembled by integrating epitaxial SCFs and composite converters into the OSRAM LBE 6SG blue LED chip (ams OSRAM AG, 8141, Premstaetten, Austria) with a peak emission wavelength of 450 nm. These chips operated at a fixed forward bias voltage of 2.6 V and a drive current of 20 mA.
The emission spectra of the prototypes, presented in Figure 4, correspond to converters containing CYMSSG:Ce SCFs with varying contents and thicknesses, grown on undoped (Series A) and Ce3+-doped (Series B) YAG substrates, each with a thickness of 0.5 mm (see Table 1 for details). For comparison, an emission diagram of the YAG:Ce substrate (Figure 4c), used as a conventional reference sample, is also provided alongside the corresponding diagram of the composite CYMSSG:Ce/YAG:Ce structures (Figure 4b).
The emission spectrum generated by these white LED prototypes demonstrates a clear dependence of Ce3+ emission intensity on the thickness of the CYMSSG:Ce SCF (Figure 4a,b). As the film thickness increases, a larger number of Ce3+ ions are excited by the incident blue light, resulting in the stronger absorption of the blue component. This, in turn, enables the tailoring of the blue-to-yellow emission ratio (Figure 4a,b). Specifically, the addition of emission from the CYMSSG:Ce SCFs significantly reduces the blue component and increases the yellow and red components in the total emission of the composite prototypes, compared to conventional YAG:Ce crystal converters.
For a more detailed analysis, the emission of WLED prototypes is plotted also in a CIE diagram (Figure 5). Table 2 presents the CIE chromaticity coordinates, color rendering index (CRI), correlated color temperature (CCT), and luminous efficiency (LE) of the developed WLEDs, highlighting their effectiveness in achieving desirable lighting characteristics. These parameters are critical for evaluating the lighting performance of the developed prototypes, providing insight into their color accuracy, spectral balance, and suitability for various applications.
CYMSSG:Ce SCF samples from Series A, grown on undoped YAG substrates, exhibited emission coordinates clustered within the blue region of the chromaticity diagram (Figure 5). Coordinates corresponding to the YAG substrates were not included here, as these substrates do not contribute to photoconversion and their emission characteristics remain identical to those of the original blue diode. This indicates that the photoconversion behavior of the CYMSSG:Ce SCF/YAG structures is determined solely by the properties of the films, without additional contributions from the substrate. Meanwhile, the conversion efficiency of these films, with thicknesses ranging from 19 to 50 μm, is low, and only the 67 μm-thick SCF A4 sample shows a clear visible trend in CIE coordinate change with increasing thickness (yellow squares in Figure 5).
The coordinates of the YAG:Ce crystal substrates (blue squares) are also plotted on the diagram as reference samples for comparison with film and composite converters (Figure 5). As shown in Figure 5, the color coordinates of the YAG:Ce crystal converters are significantly influenced by the Ce3+ concentration. In particular, the YAG:Ce crystal, with 0.075% Ce3+ content (sample C3) and a thickness of 0.5 mm, exhibits CIE coordinates of (x = 0.305, y = 0.338) and a correlated color temperature (CCT) of 6840 K, which are very close to the standard white light reference. In contrast, samples C1 and C2, with lower Ce3+ contents (0.05%), show color coordinates that fall within the sky-blue region. Moreover, increasing the Ce3+ content in the YAG:Ce crystal converters results in a slight decrease in the CRI value, but a notable improvement in luminous efficiency from 71 to 72 for samples C1 and C2, and to 79 for sample C3 (Table 2).
In contrast, CYMSSG:Ce SCF/YAG:Ce composite converters (Series B) exhibited emission coordinates in the green-yellow region (red squares). This pronounced shift is primarily attributed to the presence of Ce3+ dopant in the SCF converters, which introduces additional photoluminescent features, thereby enhancing the overall emission and significantly altering the photoconversion behavior of the epitaxial structures. In this case, the color coordinates and CCT are less dependent on the properties and Ce3+ content of the underlying crystal substrates. Instead, the composition of the SCF converters, specifically, the ratio of Y/Mg/Sc cations as well as the film thickness, play a more dominant role in determining the photoconversion characteristics of the composites (Figure 5). These parameters can be effectively tuned to optimize the performance of the fabricated WLEDs. Notably, as the SCF thickness increases, the composite converters show a reduction in the color rendering index (CRI), with values in the range of 59–62. However, they demonstrate a significantly higher luminous efficiency, reaching 102–115 lm/W, compared to the corresponding YAG:Ce substrates (Table 2), primarily due to the enhanced absorption and emission properties of both the film and substrate converters. The highest luminous efficacy achieved is 115 lm/W for sample S3.
Thus, the proposed approach for creating composite color converters demonstrates the ability to achieve virtually any desired color coordinates within the white light region by adjusting several key parameters: (i) the Ce3+ concentration in the YAG:Ce substrate, (ii) the film composition, and (iii) the film thickness. The results also highlight the critical role of both the film and substrate composition, as well as the SCF thickness, in determining the photoconversion performance of these composite converters. By carefully tuning these parameters, it is possible to tailor the colorimetric properties of pc-WLEDs to meet the specific requirements of various white solid-state lighting applications. This study illustrates the potential of CYMSSG:Ce SCFs as highly versatile and effective materials for next-generation pc-WLED technologies, paving the way for further advancements in the field.

6. Conclusions

This study investigates the structural, luminescent, and photoconversion properties of Ce3+-doped film–crystal composite converters based on epitaxial structures containing Ce3+-doped single crystalline films (SCFs) of Ca2−xY1+xMg1+xSc1−xSi3O12:Ce (x = 0–0.25) (CYMSSG:Ce), grown using the liquid phase epitaxy (LPE) method on Y3Al5O12 (YAG) and YAG:Ce substrates. For this purpose, two series of CYMSSG:Ce SCFs with different ratios of Y, Mg, and Sc cations and varying thicknesses in the 19–67 µm range were synthesized on YAG and YAG:Ce substrates.
X-ray diffraction (XRD) analysis confirmed the presence of the epitaxial growth of high-quality SCFs, revealing a lattice misfit between the CYMSSG:Ce SCF and the YAG substrate in the range of 2.51–2.57%. Absorption spectra exhibited broad bands around 340 nm and 436–458 nm, characteristic of Ce3+ 4f–5d transitions, confirming the successful doping of CYMSSG:Ce SCFs. A weak absorption band below 300 nm suggests trace Pb2+ impurities resulting from the LPE growth process using a PbO-based flux.
Photoluminescence (PL) measurements of Ca2−xY1+xMg1+xSc1−xSi3O12:Ce showed broad green-yellow emission bands due to Ce3+ transitions. Increasing the Y and Mg content (x) in the films led to a red shift in the Ce3+ emission spectra, while the SCF of this garnet with a large Sc content demonstrated a more pronounced blue shift of Ce3+ luminescence. Excitation spectra revealed prominent peaks at 340 and 450 nm related to the 4f-5d1,2 Ce3+ transitions, while a peak near 375 nm was attributed to F+ centers.
Prototype phosphor-converted white LEDs (pc-WLEDs) were fabricated using CYMSSG:Ce SCF/YAG substrate and CYMSSG:Ce SCF/YAG:Ce substrate structures with various SCF thicknesses placed directly onto blue-emitting InGaN chips. We found that films grown on undoped YAG substrates (Series A) displayed very low conversion efficiency, while the CYMSSG:Ce SCF/YAG:Ce substrate structures (Series B) exhibited promising characteristics for white LED applications. Chromaticity analysis of the latter structures demonstrated that both the YAG:Ce substrate and the CYMSSG:Ce SCF with different contents and thicknesses significantly affect the photoconversion performance of the WLED prototypes and can be used for the effective tuning of the tone of white light on demand. Namely, increasing the SCF thickness results in a slight decrease in the CRI value, but a notable improvement in the luminous efficiency of composite converters. The highest luminous efficacy of 115 lm/W is achieved for the Ca1.75Y1.25Mg1.25 Sc0.75Si3O12:Ce SCF (22 μm)/YAG:Ce (0.12%) substrate composite sample.

Author Contributions

A.S. collected and analyzed the structural and optical properties of samples and participated in the writing and preparation of the paper; V.G. perform the growth of the samples; A.F. perform XRD measurements; T.Z. participated in measurements of absorption PL and PLE; Y.Z. conceptually contributed to the research, analyzed whole experimental materials, and participated in the writing and correction of the paper. All authors have read and agreed to the published version of the manuscript.

Funding

The investigations were performed in the frameworks of the Polish National Scinentic Centre (NCN) No 2022/45/B/ST8/01757 project and also supported by the Ministry of Science and High Education of Poland in the framework of Regional Excellence Initiative nr RID/SP/0048/2024/01 project.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original data presented in this study are included in the article as figures embedded in the Word version of the paper. These figures can be opened and accessed using any version of Origin software. For further inquiries, please contact the corresponding authors.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Pimputkar, S.; Speck, J.S.; DenBaars, S.P.; Nakamura, S. Prospects for LED lighting. Nat. Photon. 2009, 3, 180–182. [Google Scholar] [CrossRef]
  2. Schubert, E.F.; Kim, J.K. Solid-State Light Sources Getting Smart. Science 2005, 308, 1274–1278. [Google Scholar] [CrossRef]
  3. Pust, P.; Schmidt, P.J.; Schnick, W. A revolution in lighting. Nat. Mater. 2015, 14, 454–458. [Google Scholar] [CrossRef]
  4. Sun, C.-C.; Chang, Y.-Y.; Yang, T.-H.; Chung, T.-Y.; Chen, C.-C.; Lee, T.-X.; Li, D.-R.; Lu, C.-Y.; Ting, Z.-Y.; Glorieux, B.; et al. Packaging efficiency in phosphor-converted white LEDs and its impact to the limit of luminous efficacy. J. Solid State Light. 2014, 1, 19. [Google Scholar] [CrossRef]
  5. Schlotter, P.; Schmidt, R.; Schneider, J. Luminescence conversion of blue light emitting diodes. Appl. Phys. A Mater. Sci. Amp. Process. 1997, 64, 417–418. [Google Scholar] [CrossRef]
  6. Nakamura, S.; Senoh, M.; Iwasa, N.; Nagahama, S.; Yamada, T.; Mukai, T. Superbright Green InGaN Single-Quantum-Well-Structure Light-Emitting Diodes. Jpn. J. Appl. Phys. 1995, 34, L1332. [Google Scholar] [CrossRef]
  7. Meng, Q.; Zhao, G.; Zhu, Q.; Li, X.; Sun, X.; Li, J.-G. Site-selective and cooperative doping of Gd3Al5O12:Ce garnets for structural stabilization and warm WLED lighting of low CCT and high CRI. Dalton Trans. 2022, 51, 645–654. [Google Scholar] [CrossRef]
  8. Lin, Y.-C.; Bettinelli, M.; Karlsson, M. Unraveling the Mechanisms of Thermal Quenching of Luminescence in Ce3+-Doped Garnet Phosphors. Chem. Mater. 2019, 31, 3851–3862. [Google Scholar] [CrossRef]
  9. Xia, Z.; Meijerink, A. Ce3+-Doped garnet phosphors: Composition modification, luminescence properties and applications. Chem. Soc. Rev. 2017, 46, 275–299. [Google Scholar] [CrossRef]
  10. Nishiura, S.; Tanabe, S.; Fujioka, K.; Fujimoto, Y. Properties of transparent Ce:YAG ceramic phosphors for white LED. Opt. Mater. 2011, 33, 688–691. [Google Scholar] [CrossRef]
  11. Bando, K.; Sakano, K.; Noguchi, Y.; Shimizu, Y. Development of high-bright and pure-white LED lamps. J. Light Vis. Environ. 1998, 22, 2–5. [Google Scholar] [CrossRef]
  12. Lee, H.-M.; Cheng, C.-C.; Huang, C.-Y. The synthesis and optical property of solid-state-prepared YAG:Ce phosphor by a spray-drying method. Mater. Res. Bull. 2009, 44, 1081–1085. [Google Scholar] [CrossRef]
  13. Huang, B.; Ma, Y.; Qian, S.; Zou, D.; Zheng, G.; Dai, Z. Luminescent properties of low-temperature-hydrothermally-synthesized and post-treated YAG:Ce (5%) phosphors. Opt. Mater. 2014, 36, 1561–1565. [Google Scholar] [CrossRef]
  14. Zhang, S.; Zhuang, W.; He, T.; Liu, Y.; Liu, R.; Gao, W.; Hu, Y.; Long, Z. Study on co-precipitation synthesized Y3Al5O12:Ce yellow phosphor for white LED. J. Rare Earths 2010, 28, 713–716. [Google Scholar] [CrossRef]
  15. Kang, Y.C.; Lenggoro, I.W.; Park, S.B.; Okuyama, K. YAG:Ce phosphor particles prepared by ultrasonic spray pyrolysis. Mater. Res. Bull. 2000, 35, 789–798. [Google Scholar] [CrossRef]
  16. Zhang, L.; Lu, Z.; Zhu, J.; Yang, H.; Han, P.; Chen, Y.; Zhang, Q. Citrate sol-gel combustion preparation and photoluminescence properties of YAG:Ce phosphors. J. Rare Earths 2012, 30, 289–296. [Google Scholar] [CrossRef]
  17. Gupta, K.V.K.; Muley, A.; Yadav, P.; Joshi, C.P.; Moharil, S.V. Combustion synthesis of YAG:Ce and related phosphors. Appl. Phys. B 2011, 105, 479–484. [Google Scholar] [CrossRef]
  18. Bierhuizen, S.; Krames, M.; Harbers, G.; Weijers, G. Performance and trends of high power light emitting diodes. In Proceedings of SPIE; Ferguson, I.T., Narendran, N., Taguchi, T., Ashdown, I.E., Eds. SPIE: Bellingham, WA, USA, 2007. [Google Scholar] [CrossRef]
  19. Allen, C.; Steckl, A.J. A nearly ideal phosphor-converted white light-emitting diode. Appl. Phys. Lett. 2008, 92, 143309. [Google Scholar] [CrossRef]
  20. Kim, Y.H.; Viswanath, N.S.M.; Unithrattil, S.; Kim, H.J.; Im, W.B. Review—Phosphor plates for high-power LED applications: Challenges and opportunities toward perfect lighting. ECS J. Solid State Sci. Technol. 2018, 7, R3134–R3147. [Google Scholar] [CrossRef]
  21. Fujita, S.; Sakamoto, A.; Tanabe, S. Luminescence characteristics of YAG glass—Ceramic phosphor for white LED. IEEE J. Sel. Top. Quantum Electron. 2008, 14, 1387–1391. [Google Scholar] [CrossRef]
  22. Víllora, E.G.; Arjoca, S.; Inomata, D.; Shimamura, K. Single-crystal phosphors for high-brightness white LEDs/LDs. In Proceedings of SPIE; Jeon, H., Tu, L.-W., Krames, M.R., Strassburg, M., Eds. SPIE: Bellingham, WA, USA, 2016. [Google Scholar] [CrossRef]
  23. Arjoca, S.; Víllora, E.G.; Inomata, D.; Aoki, K.; Sugahara, Y.; Shimamura, K. Temperature dependence of Ce:YAG single-crystal phosphors for high-brightness white LEDs/LDs. Mater. Res. Express 2015, 2, 055503. [Google Scholar] [CrossRef]
  24. Nizhankovskyi, S.V.; Tan’ko, A.V.; Savvin, Y.N.; Krivonogov, S.I.; Budnikov, A.T.; Voloshin, A.V. Single crystalline YAG:Ce phosphor for powerful solid-state sources of white light. The influence of production conditions on luminescence properties and lighting characteristics. Opt. Spectrosc. 2016, 120, 915–921. [Google Scholar] [CrossRef]
  25. Chao, W.-H.; Wu, R.-J.; Wu, T.-B. Structural and luminescent properties of YAG:Ce thin film phosphor. J. Alloys Compd. 2010, 506, 98–102. [Google Scholar] [CrossRef]
  26. Hsu, C.T.; Yen, S.K. Electrochemical synthesis of thin film YAG on inconel substrate. Electrochem. Solid State Lett. 2006, 9, D9. [Google Scholar] [CrossRef]
  27. Lee, Y.K.; Oh, J.R.; Do, Y.R. Enhanced extraction efficiency of Y2O3:Eu3+ thin-film phosphors coated with hexagonally close-packed polystyrene nanosphere monolayers. Appl. Phys. Lett. 2007, 91, 041907. [Google Scholar] [CrossRef]
  28. Bai, G.R.; Chang, H.L.M.; Foster, C.M. Erratum: “Preparation of single-crystal Y3Al5O12 thin film by metalorganic chemical vapor deposition”. Appl. Phys. Lett. 1994, 65, 790. [Google Scholar] [CrossRef]
  29. Díaz-Torres, L.A.; De la Rosa, E.; Salas, P.; Angeles-Chavez, C.; Arenas, L.B.; Nieto, J. Nanoparticle thin films of nanocrystalline YAG by pulsed laser deposition. Opt. Mater. 2005, 27, 1217–1220. [Google Scholar] [CrossRef]
  30. Mauk, M.G. Liquid-Phase Epitaxy. In Digital Encyclopedia of Applied Physics; Wiley: Hoboken, NJ, USA, 2023; pp. 1–31. [Google Scholar] [CrossRef]
  31. Capper, P.; Mauk, M. Liquid Phase Epitaxy of Electronic, Optical and Optoelectronic Materials; John Wiley & Sons: Hoboken, NJ, USA, 2007. [Google Scholar]
  32. Kundaliya, D.; Raukas, M.; Scotch, A.M.; Hamby, D.; Mishra, K.; Stough, M. Wavelength Converter for an LED and LED Containing. Same. Patent 8,937,332, 20 January 2015. [Google Scholar]
  33. Markovskyi, A.; Gorbenko, V.; Yokosawa, T.; Will, J.; Spiecker, E.; Batentschuk, M.; Elia, J.; Fedorov, A.; Pakuła, M.; Kaczmarek, M.; et al. Structural, luminescence and photoconversion properties of Lu3Al5O12:Ce single crystalline film phosphors for WLED application. J. Alloys Compd. 2022, 929, 167159. [Google Scholar] [CrossRef]
  34. Markovskyi, A.; Gorbenko, V.; Zorenko, T.; Yokosawa, T.; Will, J.; Spiecker, E.; Batentschuk, M.; Elia, J.; Fedorov, S.; Zorenko, Y. LPE growth of Tb3Al5O12:Ce single crystalline film converters for WLED application. CrystEngComm 2021, 23, 3212–3219. [Google Scholar] [CrossRef]
  35. VChani, I.; Yoshikawa, A.; Machida, H.; Fukuda, T. (Tb,Yb)3Al5O12 garnet: Crystal-chemistry and fiber growth by micro-pulling-down technique. Mater. Sci. Eng. B Solid State Mater. Adv. Technol. 2000, 75, 53–60. [Google Scholar] [CrossRef]
  36. Markovskyi, A.; Gorbenko, V.; Zorenko, T.; Witkiewicz-Lukaszek, S.; Sidletskiy, O.; Fedorov, A.; Zorenko, Y. Development of Three-Layered Composite Color Converters for White LEDs Based on the Epitaxial Structures of YAG:Ce, TbAG:Ce and LuAG:Ce Garnets. Materials 2023, 16, 1848. [Google Scholar] [CrossRef]
  37. Setlur, A.A.; Heward, W.J.; Gao, Y.; Srivastava, A.M.; Chandran, R.G.; Shankar, M.V. Crystal Chemistry and Luminescence of Ce3+-Doped Lu2CaMg2(Si,Ge)3O12 and Its Use in LED Based Lighting. Chem. Mater. 2006, 18, 3314. [Google Scholar] [CrossRef]
  38. Shimomura, Y.; Honma, T.; Shigeiwa, M.; Akai, T.; Okamoto, K.; Kijima, N. Photoluminescence and Crystal Structure of Green-Emitting Ca3Sc2Si3O12:Ce3+ Phosphor for White Light Emitting Diodes. J. Electrochem. Soc. 2007, 154, J35. [Google Scholar] [CrossRef]
  39. Katelnikovas, A.; Bettentrup, H.; Uhlich, D.; Sakirzanovas, S.; Jüstel, T.; Kareiva, A. Synthesis and optical properties of Ce3+-doped Y3Mg2AlSi2O12 phosphors. J. Lumin. 2009, 129, 1356. [Google Scholar] [CrossRef]
  40. Katelnikovas, A.; Bareika, T.; Vitta, P.; Jüstel, T.; Winkler, H.; Kareiva, A.; Žukauskas, A.; Tamulaitis, G. Y3−xMg2AlSi2O12: Cex3+ phosphors—Prospective for warm-white light emitting diodes. Opt. Mater. 2010, 32, 1261. [Google Scholar] [CrossRef]
  41. Katelnikovas, A.; Jurkevičius, J.; Kazlauskas, K.; Vitta, P.; Jüstel, T.; Kareiva, A.; Žukauskas, A.; Tamulaitis, G. Efficient cerium-based sol–gel derived phosphors in different garnet matrices for light-emitting diodes. J. Alloys Compd. 2011, 509, 6247. [Google Scholar] [CrossRef]
  42. Katelnikovas, A.; Ogiegło, J.M.; Winkler, H.; Kareiva, A.; Jüstel, T. Synthesis of Y3−xLuxAl3MgSiO12 garnet powders by sol–gel method. J. Sol-Gel Sci. Technol. 2011, 59, 311. [Google Scholar] [CrossRef]
  43. Katelnikovas, A.; Plewa, J.; Dutczak, D.; Möller, S.; Enseling, D.; Winkler, H.; Kareiva, A.; Jüstel, T. Synthesis and optical properties of green emitting garnet phosphors for phosphor-converted light emitting diodes. Opt. Mater. 2012, 34, 1195. [Google Scholar] [CrossRef]
  44. Katelnikovas, A.; Sakirzanovas, S.; Dutczak, D.; Plewa, J.; Enseling, D.; Winkler, H.; Kareiva, A.; Jüstel, T. Synthesis and optical properties of yellow emitting garnet phosphors for pcLEDs. J. Lumin. 2013, 136, 17. [Google Scholar] [CrossRef]
  45. Zhong, J.; Zhuang, W.; Xing, X.; Liu, R.; Li, Y.; Liu, Y.; Hu, Y. Synthesis, Crystal Structures, and Photoluminescence Properties of Ce3+-Doped Ca2LaZr2Ga3O12: New Garnet Green-Emitting Phosphors for White LEDs. J. Phys. Chem. C 2015, 119, 5562. [Google Scholar] [CrossRef]
  46. Pan, Z.; Xu, Y.; Hu, Q.; Li, W.; Zhou, H.; Zheng, Y. Combination cation substitution tuning of yellow-orange emitting phosphor Mg2Y2Al2Si2O12:Ce3+. RSC Adv. 2015, 5, 9489. [Google Scholar] [CrossRef]
  47. Cao, L.; Li, W.; Devakumar, B.; Ma, N.; Huang, X.; Lee, A.F. Full-Spectrum White Light-Emitting Diodes Enabled by an Efficient Broadband Green-Emitting CaY2ZrScAl3O12:Ce3+ Garnet Phosphor. ACS Appl. Mater. Interfaces 2022, 14, 5643–5652. [Google Scholar] [CrossRef] [PubMed]
  48. Huang, X.; Chan, J.; Chen, X. A well-performed green-emitting Lu1.5Ca1.5Al3.5Si1.5O12:Ce3+ garnet phosphor for high-quality pc-WLEDs. Ceram. Int. 2024, 50, 55979–55986. [Google Scholar] [CrossRef]
  49. Khaidukov, N.; Zorenko, T.; Iskaliyeva, A.; Paprocki, K.; Batentschuk, M.; Osvet, A.; Van Deun, R.; Zhydaczevskii, Y.; Suchocki, A.; Zorenko, Y. Synthesis and luminescent properties of prospective Ce3+ doped silicate garnet phosphors for white LED convertors. J. Lumin. 2017, 192, 328–336. [Google Scholar] [CrossRef]
  50. Levchuk, I.; Osvet, A.; Brabec, C.J.; Batentschuk, M.; Shakhno, A.; Zorenko, T.; Zorenko, Y. Micro-powder Ca3Sc2Si3O12:Ce silicate garnets as efficient light converters for WLEDs. Opt. Mater. 2020, 107, 109978. [Google Scholar] [CrossRef]
  51. Khaidukov, N.; Zorenko, Y.; Zorenko, T.; Iskaliyeva, A.; Paprocki, K.; Zhydachevskii, Y.; Suchocki, A.; Van Deun, R.; Batentschuk, M. New Ce3+ doped Ca2YMgScSi3O12 garnet ceramic phosphor for white LED converters. Phys. Rapid Res. Lett. 2017, 11, 1700016. [Google Scholar] [CrossRef]
  52. Xian, C.; Chen, X.; Huang, X. High-performance green-emitting Ca2YScAl2Si2O12:Ce3+ garnet phosphors and their applications in high-quality blue-chip-pumped white LEDs. J. Mater. Chem. C 2024, 12, 12378–12388. [Google Scholar] [CrossRef]
  53. Gorbenko, V.; Zorenko, T.; Paprocki, K.; Iskaliyeva, A.; Fedorov, A.; Schröppel, F.; Levchuk, I.; Osvet, A.; Batentschuk, M.; Zorenko, Y. Epitaxial growth of single crystalline film phosphors based on the Ce3+-doped Ca2YMgScSi3O12 garnet. CrystEngComm 2017, 19, 3689–3697. [Google Scholar] [CrossRef]
  54. Shakhno, A.; Gieszczyk, W.; Bilski, P.; Witkiewicz-Łukaszek, S.; Zorenko, T.; Cieszko, M.; Szczepański, Z.; Kotlov, A.; Zorenko, Y. Luminescence and photoconversion properties of Ce-doped Ca3Sc2Si3O12 crystal. J. Lumin. 2024, 266, 120311. [Google Scholar] [CrossRef]
  55. Zorenko, Y.; Batentschuk, M.; Brabec, C.; Osvet, A.; Gorbenko, V.; Levchuk, I.; Zorenko, T.; Chepyga, L.; Markovskiy, A.; Witkiewicz-Lukaszek, S. Patent Application EU EP 3831911A1 Composite Wavelength Converter. Application. EP19213887A, 5 December 2019. [Google Scholar]
  56. Shakhno, A.; Witkiewicz-Łukaszek, S.; Gorbenko, V.; Zorenko, T.; Zorenko, Y. Composite color converters based on the Ca3Sc2Si3O12:Ce single crystalline films. Opt. Mater. X 2024, 22, 100328. [Google Scholar] [CrossRef]
  57. Gorbenko, V.; Zorenko, T.; Witkiewicz-Łukaszek, S.; Shakhno, A.; Osvet, A.; Batentschuk, M.; Fedorov, A.; Zorenko, Y. Crystallization and Investigation of the Structural and Optical Properties of Ce3+-Doped Y3−xCaxAl5−ySiyO12 Single Crystalline Film Phosphors. Crystals 2021, 11, 788. [Google Scholar] [CrossRef]
  58. Zhu, J.; Sidletskiy, O.; Boyaryntseva, Y.; Grynyov, B. Structure and role of carbon-related defects in yttrium aluminum garnet. Opt. Mater. 2021, 11, 110561. [Google Scholar] [CrossRef]
Materials 18 03590 g001
Figure 1. XRD patterns of (12 0 0) plane of Ca2YMgScSi3O12:Ce SCF (sample B1) and Ca1.75Y1.25Mg1.25Sc0.75Si3O12:Ce SCFs (sample B4) grown on YAG substrate.
Figure 1. XRD patterns of (12 0 0) plane of Ca2YMgScSi3O12:Ce SCF (sample B1) and Ca1.75Y1.25Mg1.25Sc0.75Si3O12:Ce SCFs (sample B4) grown on YAG substrate.
Materials 18 03590 g001
Materials 18 03590 g002
Figure 2. RT absorption spectra of CYMSSG:Ce SCF/YAG (a) and CYMSSG:Ce SCF/YAG:Ce (b) in comparison with YAG:Ce substrates (c).
Figure 2. RT absorption spectra of CYMSSG:Ce SCF/YAG (a) and CYMSSG:Ce SCF/YAG:Ce (b) in comparison with YAG:Ce substrates (c).
Materials 18 03590 g002
Materials 18 03590 g003
Figure 3. RT PL (a,c,e) and PLE (b,d,f) spectra of CYMSSG:Ce SCF/YAG ((a,b)—A-series) and CYMSSG:Ce/YAG:Ce ((c,d)—B series) structures in comparison with YAG:Ce substrates ((c)—series C).
Figure 3. RT PL (a,c,e) and PLE (b,d,f) spectra of CYMSSG:Ce SCF/YAG ((a,b)—A-series) and CYMSSG:Ce/YAG:Ce ((c,d)—B series) structures in comparison with YAG:Ce substrates ((c)—series C).
Materials 18 03590 g003
Materials 18 03590 g004
Figure 4. Normalized emission spectra of pc-WLED prototypes fabricated on the base of 450 nm LED chip and CYMSSG:Ce SCF converters grown on YAG (a) and YAG:Ce (b) substrates in comparison with converters on the base of YAG:Ce crystal substrates (c).
Figure 4. Normalized emission spectra of pc-WLED prototypes fabricated on the base of 450 nm LED chip and CYMSSG:Ce SCF converters grown on YAG (a) and YAG:Ce (b) substrates in comparison with converters on the base of YAG:Ce crystal substrates (c).
Materials 18 03590 g004
Materials 18 03590 g005
Figure 5. Chromaticity diagram of a WLED prototype fabricated on the base of 450 nm LED chip and CYMSSG:Ce SCFs grown on YAG (Series A) and YAG:Ce (Series B) substrates. The results for YAG:Ce substrates are presented for comparison.
Figure 5. Chromaticity diagram of a WLED prototype fabricated on the base of 450 nm LED chip and CYMSSG:Ce SCFs grown on YAG (Series A) and YAG:Ce (Series B) substrates. The results for YAG:Ce substrates are presented for comparison.
Materials 18 03590 g005
Table 1. The nominal composition (in melt solution) and the measured (using EDX) composition of LPE-grown CYMSSG:Ce/YAG and CYMSSG:Ce/YAG:Ce films (Series A and B, respectively) and YAG:Ce substrates (Series C).
Table 1. The nominal composition (in melt solution) and the measured (using EDX) composition of LPE-grown CYMSSG:Ce/YAG and CYMSSG:Ce/YAG:Ce films (Series A and B, respectively) and YAG:Ce substrates (Series C).
SampleNominal Content in the MeltMeasured SCF Compositionh, µm
A1Ca2YMgScSi3O12:CeCa1.88Y1.09Ce0.01Mg0.9Sc1.42Si2.73O1219
A2Ca2YMgScSi3O12:CeCa1.83Y1.08Ce0.03Mg0.9Sc1.51Si2.68O1234
A3Ca2YMgScSi3O12:CeCa1.81Y1.12Ce0.03Mg0.93Sc1.48Si2.67O1249
A4Ca1.75Y1.25Mg1.25Sc0.75Si3O12:CeCa1.63Y1.27Ce0.03Mg1.19Sc1.27Si2.72O1267
B1Ca2YMgScSi3O12:CeCa1.92Y1.08Ce0.02Mg0.95Sc1.27Si2.78O1210
B2Ca1.75Y1.25Mg1.25Sc0.75Si3O12:CeCa1.65Y1.35Ce0.03Mg1.18Sc0.61Si3.21O1211
B3Ca1.75Y1.25Mg1.25Sc0.75Si3O12:CeCa1.68Y1.32Ce0.03Mg1.28Sc0.71Si3.01O1222
C1Y3Al5O12:CeY2.99Ce0.01Al5O12500
C2Y3Al5O12:CeY2.99Ce0.01Al5O12500
C3Y3Al5O12:CeY2.988Ce0.012Al5O12500
Table 2. Comparison of the CIE coordinates, CRI, CCT, and LE of epitaxial structures based on the CYMSSG:Ce SCF samples grown on YAG (Series A, Series B) and YAG:Ce (Series C) substrates. The results for YAG:Ce substrates, as reference samples, are presented for comparison.
Table 2. Comparison of the CIE coordinates, CRI, CCT, and LE of epitaxial structures based on the CYMSSG:Ce SCF samples grown on YAG (Series A, Series B) and YAG:Ce (Series C) substrates. The results for YAG:Ce substrates, as reference samples, are presented for comparison.
SamplesSCF Thicknesses, µmType and Thicknesses
of Substrate, mm		CIE CoordinatesCCT, KCRILE,lm/W
yy
Series A
A1190.50.1620.066 --
A2340.50.1550.043 --
A3490.50.1560.047 --
A4670.50.1890.146 --
Series B
B110C1; 0.50.3460.428515062102
B211C2; 0.50.3740.475461259112
B322C3; 0.50.3880.496440659115
Series C
C1-0.50.2630.263-7871
C2-0.50.2760.278-7572
C3-0.50.3050.33868387079
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Shakhno, A.; Gorbenko, V.; Zorenko, T.; Fedorov, A.; Zorenko, Y. Optical and Photoconversion Properties of Ce3+-Doped (Ca,Y)3(Mg,Sc)2Si3O12 Films Grown via LPE Method onto YAG and YAG:Ce Substrates. Materials 2025, 18, 3590. https://doi.org/10.3390/ma18153590

AMA Style

Shakhno A, Gorbenko V, Zorenko T, Fedorov A, Zorenko Y. Optical and Photoconversion Properties of Ce3+-Doped (Ca,Y)3(Mg,Sc)2Si3O12 Films Grown via LPE Method onto YAG and YAG:Ce Substrates. Materials. 2025; 18(15):3590. https://doi.org/10.3390/ma18153590

Chicago/Turabian Style

Shakhno, Anna, Vitalii Gorbenko, Tetiana Zorenko, Aleksandr Fedorov, and Yuriy Zorenko. 2025. "Optical and Photoconversion Properties of Ce3+-Doped (Ca,Y)3(Mg,Sc)2Si3O12 Films Grown via LPE Method onto YAG and YAG:Ce Substrates" Materials 18, no. 15: 3590. https://doi.org/10.3390/ma18153590

APA Style

Shakhno, A., Gorbenko, V., Zorenko, T., Fedorov, A., & Zorenko, Y. (2025). Optical and Photoconversion Properties of Ce3+-Doped (Ca,Y)3(Mg,Sc)2Si3O12 Films Grown via LPE Method onto YAG and YAG:Ce Substrates. Materials, 18(15), 3590. https://doi.org/10.3390/ma18153590

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