Generative Synthesis of Highly Stable Perovskite Nanocrystals via Mesoporous Silica for Full‐Spectrum White LED

Abstract

Perovskite nanocrystals with CsPbX₃ (X = Cl, Br, or I) structure have attracted great attention for developing optoelectronic applications in the past few years. However, their low stability and the limited scalability of current synthesis methods pose major challenges for future applications. Here, a template‐assisted strategy is reported for synthesizing CsPbCl₃ nanocrystals within mesoporous silica nanoreactors. Powder state CsPbCl₃ complex fabricated via this method demonstrated an exceptional solvent stability and allows for yttrium doping to further enhance optical performance. Halide tuning (Cl⁻ to Br⁻) and synthesis of lead‐free perovskites such as Cs₄Bi₂MnCl₁₂ enable broad spectral emission, supporting full‐spectrum white LED fabrication. This low‐cost, scalable, and reproducible method offers strong potential for advancing perovskite‐based optoelectronic technologies.

Crystals under Control! Cesium lead halide perovskite nanocrystals (PNCs) are synthesized inside mesoporous silica nanoreactors, yielding highly stable and color‐tunable emitters. Yttrium doping enhances photoluminescence intensity of PNCs, while halide tuning adjusts emission colors. Combining these nanocrystals with Cs₄MnBi₂Cl₁₂ PNCs leads to a white‐light‐emitting LED with full‐spectrum tunability.

1. Introduction

Inorganic lead halide perovskite nanocrystals (PNCs) with the composition CsPbX₃ (X = Cl, Br, I) are widely investigated due to their high photoluminescence (PL) quantum yield (60–95%) and narrow full width at half‐maximum (FWHM) of the emission peak.^{[ 1} , ² , ³ , ⁴ , ⁵ , ^{6 ]} They have been applied for various optoelectronic applications, including light‐emitting diodes (LEDs), lasers, and photodetectors.^{[ 7} , ⁸ , ⁹ , ^{10 ]} Despite the fascinating optical properties, lead halide PNCs confront a few challenges, including their low stability against moisture, temperature, and ultraviolet (UV) light, potential lead toxicity after decomposition, and the lack of scalable productions.^{[ 5} , ^{11 ]} In the past few years, various strategies have been applied to improve the stability of lead halide PNCs. These include dielectric elements doping with another element including tin or manganese to increase the intrinsic structure stability,^{[ 12} , ¹³ , ¹⁴ , ¹⁵ , ¹⁶ , ^{17 ]} and the development of alternative synthesis methods such as hot injection, ultrasonication, hydrothermal, and microwave‐assisted techniques, often involving tailored capping ligands or morphologies.^{[ 1} , ¹² , ¹⁸ , ¹⁹ , ²⁰ , ²¹ , ^{22 ]} Additionally, encapsulating PNCs within protective matrices and shells, such as oxides, polymers, or even other perovskite phases has been employed to improve environmental robustness and device compatibility.^{[ 1} , ¹⁵ , ^{23 ]}

Despite encouraging progresses were achieved, there remains a critical need for efficient and cost‐effective methods to synthesize lead halide perovskite nanocrystals (PNCs) with enhanced stability, which is essential for their practical application. Encapsulation within mesoporous materials has proven effective in improving stability. For instance, mesoporous metal–organic frameworks have been used to encapsulate all‐inorganic perovskite quantum dots, significantly enhancing their stability for optoelectronic devices.^{[ 23 ]} Similarly, mesoporous silica nanoparticles (MSNs) have been employed as templates for the synthesis of perovskite nanocrystals.^{[ 24} , ²⁵ , ²⁶ , ^{27 ]} Even though these studies provided insights into the synthesis of organic or bromide perovskite nanocrystals, they either required additional steps to prepare precursors as oleate salts or overlooked the development of CsPbCl₃ nanocrystals. Consequently, the scalable synthesis of stable lead chloride PNCs using mesoporous templates remains a significant challenge.^{[ 27} , ^{28 ]}

Here, we present a template‐assisted method for producing CsPbCl₃ PNCs using MSN as the nanoreactor. MSNs are amorphous nanometer‐sized particles with highly ordered porous morphology, providing an inert environment for lead halide PNC growth.^{[ 28} , ²⁹ , ³⁰ , ^{31 ]} In addition, the porous structure of MSN can collapse at high temperature and serves as the protection layers for the synthesized nanocrystals and improves their stability in a range of solvent conditions. Additionally, we demonstrated that the MSN‐PNC nanocomposite can easily intake yttrium doping to further enhance the optical properties, and enable multicolor emissions through tuning the halide group and synthesis of Cs₄Bi₂MnCl₁₂ double perovskite, facilitating photoluminescence (PL)‐driven single‐chip white color LED devices.

2. Experimental Section

2.1. Materials

All reagents were used as received without further purification, including cesium chloride (CsCl, from BioShop), lead chloride (PbCl₂, from Sigma–Aldrich), yttrium(III) chloride (YCl₃, from Sigma–Aldrich), dimethylformamide (DMF, from Fisher Scientific), dimethyl sulfoxide (DMSO, from Fisher Scientific), Hydrochloric Acid (HCl, from Fisher Scientific), tetraethoxysilane (TEOS from Sigma–Aldrich), ethanol (from Fisher Scientific), diethanolamine (DEA, from Sigma–Aldrich), cetyltrimethylammonium (CTAB, from Sigma–Aldrich), acetone (from Fisher Scientific), Bismuth(III) oxide (Bi₂O₃, from Sigma–Aldrich), cesium carbonate (Cs₂CO₃, from Sigma–Aldrich), octadecene (ODE, from Sigma–Aldrich), oleic acid (OA, from Sigma–Aldrich), oleylamine (OLA from Sigma–Aldrich).

Fabrication of Mesoporous Silica Nanoparticles (MSN) as Nanoreactor: The synthesis procedure was modified from a previously reported method to increase yield.^{[ 30} , ^{31 ]} A mixture of 60 mL ethanol, 1.8 g CTAB, and 450 µL DEA was dissolved in 150 mL deionized water under constant stirring at 60 °C until a clear solution formed. Then, 18 mL of TEOS was quickly added into the above solution. The reaction was finished by stirring for another 2 h at 60 °C in a closed environment. MSN were collected by blending with 120 mL of acetone and centrifugation at 8000 g, followed by calcination in a muffle furnace (model: CF1100; Across International) at 550 °C for 2 h with 1 h ramp time, CTAB and other organic residues were removed. Collected MSN were stored in vacuum for 2 h before further synthesis procedure.

Fabrication of Mesoporous Silica Nanoparticle‐CsPbCl₃ Nanocrystals matrix: Figure 1 illustrates the overall synthesis method. Briefly, 50 mg of pre‐synthesized mesoporous silica nanoparticles (MSNs) were mixed with 100 ul of solution containing a molar ratio of 1:1 of CsCl stock solution and PbCl₂ stock solution (lead chloride solvent system was composed of DMF/DMSO/HCl in a 7:2:1 volume ratio and cesium precursor solvent was composed of deionized water). The mixture was transferred into a long glass tube, sealed with parafilm, and a small hole was introduced at the top to allow vapor release. The tube was then placed in a vacuum oven (model: AT09‐316L‐UL; Across International) at 65 °C for 4 h to facilitate precursor infiltration. The resulting CsPbCl₃–MSN composite was subsequently transferred to crucible and calcined at 600 °C for 15 min (with a 1 h ramp time) to complete crystallization. Yttrium‐doped CsPbCl₃ was synthesized by introducing YCl₃ into the precursor mixture during the mixing stage. To produce CsPbX₃ (X = Cl, Br), CsCl and PbCl₂ were replaced with CsBr and PbBr₂ (lead salt was dissolved in a solvent system composed of DMF and DMSO in an 8:2 volume ratio).

Figure 1.

a) Schematic illustration for the typical preparation of CsPbCl₃ PNCs. b) XRD patterns of MSN (black) and MSN‐CsPbCl₃ matrix (red). c) TEM image of synthesized MSN. d) Zoomed in TEM image of MSN. e) TEM image of CsPbCl₃‐MSN matrix. f) Zoomed in TEM image of CsPbCl₃‐MSN. g) BET analysis of MSN, MSN‐CsPbCl₃ matrix from different precursor concentration (0.8, 1.0, 1.2 µmol PNCs/mg MSN). h) Pore volume distribution of MSN, MSN‐CsPbCl₃ matrix from different precursor concentration. i) PL of CsPbCl₃‐MSN prepared via different precursor concentration.

Fabrication of Mesoporous Silica Nanoparticle ‐Cs₄Bi₂MnCl₁₂ Nanocrystals matrix: Similar to MSN‐ lead halide PNCs synthesis, 50 mg of pre‐synthesized mesoporous silica nanoparticles (MSNs) were mixed with 100 ul of solution containing a molar ratio of 4:1:1 of CsCl stock solution, Bi₂O₃ stock solution and MnCl₂ stock solution (Bi₂O₃ stock were prepared in a HCl solvent system). The mixture was transferred into a long glass tube, sealed with parafilm, and a small hole was introduced at the top to allow vapor release. The tube was then placed in a vacuum oven at 120 °C for 2 h to facilitate precursor infiltration and crystallization.

Synthesis of CsPbCl₃ Nanocrystals: Colloidal CsPbCl₃ nanocrystals were synthesized via a hot‐injection method with slight modifications to a previously reported protocol.^{[ 32 ]}

Cesium precursor solution: Cesium precursor solution was prepared by mixing Cs₂CO₃ (0.407 g), oleic acid (OA, 1 mL), and octadecene (ODE, 10 mL) in a 50 mL three‐necked flask. The mixture was heated to 120 °C under vacuum for degassing, followed by nitrogen purging. The solution was then maintained at 50 °C under nitrogen for later use.

Synthesis of CsPbCl₃ Nanocrystals: Lead precursor solution was prepared by dissolving PbCl₂ (0.37 mmol) in ODE (10 mL) in a 50 mL three‐necked round‐bottom flask. The mixture was degassed under vacuum while gradually heating to 90 °C for 30 min to remove residual air and moisture. The temperature was then increased to 120 °C, and the flask was purged with nitrogen three times before being maintained under a nitrogen atmosphere for 1 h. Subsequently, OA (1 mL) and oleylamine (OLA, 1 mL) were injected into the lead precursor solution at 120 °C to facilitate the complete dissolution of PbCl₂. The temperature was then raised to 170 °C, and 0.8 mL of the preheated cesium precursor solution was swiftly injected. Nanocrystal formation occurred rapidly upon injection. After 5 s, the reaction mixture was quenched by immersion in an ice‐water bath to rapidly cool the solution to room temperature and suppress further nanocrystal growth.

Fabrication of single chip white light photoluminescence driven LED: Yttrium‐doped CsPbCl₃–MSN, CsPbClBr₂–MSN, CsPbCl₁.₅Br₁.₅–MSN, CsPbCl₂Br–MSN, CsPbBr₃–MSN, and Cs₄Bi₂MnCl₁₂–MSN powders were blended with a UV‐transparent silicone gel. The mixture was solidified on a cap and mounted onto a GaN‐based UV LED chip with a peak emission at 370 nm. The optical performance of the resulting LED devices was characterized using a FluoroMax Plus spectrofluorometer (Horiba).

Characterizations: X‐ray diffraction (XRD) patterns were acquired on a Rigaku MiniFlex600 system with a Cu radiation. Transmission electron microscopy (TEM) images were taken from using Hitachi HT7700 with acceleration voltage of 80kV. SEM images and EDS mapping were taken from using Hitachi SU7000 with acceleration voltage of 15kV. The specific surface areas were calculated by the Brunauer–Emmett– Teller (BET) method. The total pore volume was obtained from the t‐plot method (N₂, micromeritics, ASAP2460, USA). Pore size distribution was calculated from the adsorption branch of N2 adsorption/desorption isotherm and BET method. The PL spectra were prepared by using a FluoroMax Plus spectrophotometer with a Xe lamp excitation source from Horiba.

3. Result and Discussion

We took advantage of the highly porous structure in MSN for efficient absorption of large amount of water precursor solutions.^{[ 31} , ³³ , ³⁴ , ³⁵ , ^{36 ]} After thorough mixing of MSN with CsCl and PbCl₂ solutions via vortexing, the mixture was subjected to vacuum treatment to promote precursor infiltration and maintain an inert environment. The CsPbCl₃–MSN nanocomposites were formed under vacuum, followed by calcination at 600 °C (Figure 1a). X‐ray diffraction (XRD) analysis of the pristine mesoporous silica nanoparticles (MSNs) showed a broad, diffuse peak, which is characteristic of amorphous silica with no long‐range structural order.^{[ 30} , ³¹ , ^{37 ]} In contrast, the XRD pattern of the synthesized CsPbCl₃–MSN nanocomposites (0.8 µmol PNCs/mg MSN) exhibited distinct diffraction peaks that closely match the reference pattern of cubic CsPbCl₃ (JCPDS No. 04‐009‐7249), confirming the successful formation of the perovskite crystalline phase (Figure 1b).^{[ 38 ]}

The synthesized mesoporous silica nanoparticles (MSNs) exhibit a uniform spherical morphology with an average diameter of ≈200 nm, TEM images reveal a highly interconnected porous network (Figure 1c,d). Upon calcination at 600 °C, this porous framework on the surface partially collapses, effectively confining the CsPbCl₃ perovskite nanocrystals (PNCs) within the MSN matrix while retaining the overall particle morphology (Figure 1e). Magnified images of the CsPbCl₃–MSN composites confirm the formation of uniformly distributed nanocrystals with sizes ranging from 3 to 5 nm, which is consistent with the size regime required for quantum confinement and photoluminescence applications (Figure 1f). Brunauer–Emmett–Teller (BET) analysis was performed on pristine MSNs and CsPbCl₃–MSN composites synthesized with varying precursor/MSN ratios. A significant reduction in surface area from 674.42 m² g⁻¹ (MSN) to 19.75 m² g⁻¹ (at 1.2 µmol PNCs/mg MSN) indicates substantial pore filling and partial collapse of the mesoporous framework during nanocrystal formation (Figure 1g).^{[ 38 ]} Barrett–Joyner–Halenda (BJH) analysis revealed an average pore diameter of 3.08 nm in pristine MSNs, which is consistent with the micelle size of the CTAB template used during synthesis (Figure 1h).^{[ 38 ]} The pore volume also decreased from 0.59 cm³ g⁻¹ (MSN) to 0.05 cm³ g⁻¹ (1.2 µmol PNCs/mg MSN), further confirming the successful incorporation of PNCs within the mesopores of nanoreactor.

The PL of CsPbCl₃–MSN synthesized from different precursor feeding ratios were dispersed in solution measured under 365 nm wavelength excitation. A narrow PL emission peak centered at 407 nm matches the excitonic emission of CsPbCl₃ from the literature, further confirming the optical functionality of this product (Figure 1i).^{[ 39 ]} The highest PL intensity was observed at a precursor concentration of 0.8 µmol PNCs/mg MSN. At higher precursor loadings, a decline in PL intensity was noticed, which may be attributed to the growth of larger CsPbCl₃ nanocrystals within the interconnected MSN pores, resulting in reduced quantum confinement effects.

MSNs also enhance the stability of CsPbCl₃ PNCs. Conventional bottom‐up synthesis methods typically rely on surface capping ligands such as oleic acid (OA) and oleylamine (OLA) to maintain colloidal stability.^{[ 32 ]} (Table S1, Supporting Information) However, these protonated ligands are prone to detachment in polar environments (e.g., water or ethanol), which can strip halides from the PNC surface.^{[ 22 ]} This destabilization often results in hydration, decomposition, or phase transformation, ultimately degrading the photoluminescence properties of the nanocrystals. In contrast, the template‐assisted method enables the formation of PNCs without the need for surface capping ligands, while the mesoporous silica matrix provides a physical barrier that isolates the CsPbCl₃ nanocrystals from the external environment.^{[ 28} , ^{29 ]}

To visually assess the water stability of CsPbCl₃–MSN, we compared its PL behavior with colloidal CsPbCl₃ PNCs synthesized via a previously reported hot‐injection method using OA and OLA as surface ligands. CsPbCl₃–MSN retained stable PL intensity for up to 14 days in aqueous dispersion (Figure 2a). In contrast, the 10nm‐colloidal CsPbCl₃ PNCs exhibited a rapid decline, losing ≈75% of their emission intensity within 10 min of water exposure and over 99% within 2 days (Figure 2b) (Figure S1, Supporting Information). To further evaluate the chemical stability of CsPbCl₃–MSN, the nanocomposites were dispersed in ethanol at room temperature for 14 days, with PL spectra recorded every 2 days. ≈85% of the initial emission intensity was retained after 14 days (Figure 2c). Additionally, a 50% DMF–H₂O mixed solvent was used to further challenge the stability, CsPbCl₃–MSN maintained more than 80% of its PL intensity after 14 days of dispersion (Figure 2d). In comparison, colloidal CsPbCl₃ PNCs no longer exhibit any emission immediately upon dispersion in either ethanol or 50% DMF–H₂O solution.

Figure 2.

a) PL data for 14 days water stability analysis of MSN‐CsPbCl₃ with 365 nm excitation. b) PL data for 2 days water stability analysis of colloidal CsPbCl₃ with 365 nm excitation. c) PL data for 14 days ethanol stability analysis of MSN‐CsPbCl₃ with 365 nm excitation. d) PL data for 14 days 50% DMF stability analysis of MSN‐CsPbCl₃ with 365 nm excitation.

To further improve the brightness of the CsPbCl₃‐MSN nanocomposites, we introduced ion doping into the CsPbCl₃ nanocrystal. Previous research indicated that yttrium doping is a potential method for increasing the PL intensity of CsPbCl₃, as yttrium can be incorporated into the 3D perovskite grain.^{[ 40 ]} However, the traditional method is relatively complex and hard to scale up. Here, we introduced the yttrium doping in CsPbCl₃ simply by adding an yttrium chloride water solution during solution mixing stage. After yttrium doping, the PL of CsPbCl₃‐MSN has been remarkably improved (Figure 3a,b). With the increase of yttrium concentration, at the 5% doping concentration, the peak intensity of excitonic emission is around six times of the undoped sample emission, followed by a quenching of emission intensity with 7.5% doping condition. TEM images of yttrium‐doped CsPbCl₃‐MSN nanocomposites indicated that there was not a significant morphology change from the introduction of this dopant (Figure S2, Supporting Information). XRD patterns of yttrium‐doped CsPbCl₃ confirm successful doping. The main diffraction peaks shift toward higher angles, indicating a reduction in lattice spacing.^{[ 41 ]} This shift can be attributed to the smaller ionic radius of Y³⁺ compared to Pb²⁺, which leads to lattice contraction (Figure 3c,d).

Figure 3.

a) PL of CsPbCl₃ synthesized with different yttrium feeding concentration under 365 nm excitation. b) Their integrated intensity of different Y doping concentration in CsPbCl₃. c) XRD patterns of CsPbCl₃‐MSN (black), 2.5%Y: CsPbCl₃‐MSN (red), 5%Y: CsPbCl₃‐MSN (blue). d) Their enlarged XRD patterns showing the peak shift. E) SEM image of template‐assisted yttrium‐doped CsPbCl₃ nanocrystals and EDS elemental maps.

SEM imaging using the backscattered electron (BSE) detector revealed clear contrast between the yttrium‐doped CsPbCl₃ perovskite nanocrystals (PNCs) and the mesoporous silica (MSN) template, attributable to differences in atomic number (Figure 3e).^{[ 42 ]} The EDS mapping confirmed the presence of all expected elements in both the yttrium‐doped CsPbCl₃ and the MSN nanoreactor (Figure S3, Supporting Information). These results, together with TEM analysis, demonstrate the successful incorporation of yttrium dopants into the CsPbCl₃ lattice via the template‐assisted synthesis method (Figure S2, Supporting Information).

To achieve tunable white light emission, single‐color emission from yttrium‐doped CsPbCl₃ is insufficient. However, blending it with CsPbX₃ (X = Cl, Br) nanocrystals, where chlorine is partially replaced by bromine, enables emission spectrum covered from deep violet to green.^{[ 38 ]} Furthermore, introducing lead‐free Cs₄Bi₂MnCl₁₂ PNCs expands the emission to cover the full visible spectrum, facilitating the design of a full‐spectrum white LED. All of the above PNCs were successfully synthesized using MSN as the nanoreactor with slight modifications to the synthesis steps, and all exhibit emission under 365 nm UV excitation (Figure 4a; Figure S4, Supporting Information).^{[ 43 ]}

Figure 4.

a) Emission of CsPbX₃(X = Cl,Br) and Cs₄Bi₂MnCl₁₂ PNCs synthesized by nanoreactor (excitation of 365 nm). b) Illustration of white color PL‐driven LED device. c) Image of PL‐driven LED setup turned on in darkroom. d) Luminance white LED under LED excitation. e) CIE1931 diagram of five recorded point from LED.

Contrary to commercial white LEDs that rely on multiple chips emitting at different wavelengths, white light can be generated by blending various MSN‐PNCs powders and assembling them on a single 370 nm UV LED chip.^{[ 5 ]} This approach enables cost‐efficient and color‐tunable LED fabrication by adjusting the mixing ratio of different MSN‐PNCs composites.^{[ 44 ]} Figure 4b illustrates the setup, where a plastic shield confines the powder mixed with a UV‐to‐visible transparent silicone gel, and a UV GaN chip is mounted on the substrate. Figure 4c shows the resulting white light emission from the 370 nm chip with the optimized MSN‐PNCs blend.

To demonstrate the feasibility of fabricating color‐tunable LEDs, five samples were prepared with varying mixing ratios MSN‐PNCs matrices. The emission colors from each sample were characterized using a spectrofluorometer and plotted on the CIE diagram (Figure 4d,e). Emission of different MSN‐PNCs were also indicated in the diagram as they can be seen as the emission color boundary of such device. By blending the powders with silicone gel and assembling them using the described method, tunable emission colors were achieved under 370 nm LED excitation. These results confirm that MSN‐PNCs matrices are suitable for single‐chip, UV‐excited, color‐tunable LED fabrication. Due to the high stability of synthesized PNCs and the simple fabrication procedure of this method, commercializing such optoelectrical device based on PNCs can be achievable.

4. Conclusion

In summary, we developed a facile and robust method for fabricating lead halide PNCs with excellent environmental stability, maintaining strong photoluminescence in various solvent conditions over extended periods. This approach enables the synthesis of doped CsPbCl₃ and lead‐free halide PNCs, making them suitable for color‐tunable white light LED applications. Owing to the reproducibility of the synthesis and the stability of the resulting nanocrystals, this method offers strong potential for commercialization of halide PNC‐based optoelectronic devices.

Conflict of Interest

The authors declare no conflict of interest.

Supporting information

Supporting Information

Wu J., Cai H., Shen P., et al. “Generative Synthesis of Highly Stable Perovskite Nanocrystals via Mesoporous Silica for Full‐Spectrum White LED.” Small 21, no. 36 (2025): 21, 2507240. 10.1002/smll.202507240

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.