Nanocomposites of Perovskite Quantum Dots Embedded in

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C: Plasmonics; Optical, Magnetic, and Hybrid Materials

Nanocomposites of Perovskite Quantum Dots Embedded in Magnesium Silicate Hollow Spheres for Multi-Color Display Zhenfu Zhao, Zhihai Wu, Jiong Cheng, Liang Jing, and Yafei Hou J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.8b03721 • Publication Date (Web): 03 Jul 2018 Downloaded from http://pubs.acs.org on July 3, 2018

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The Journal of Physical Chemistry

1

Nanocomposites of Perovskite Quantum Dots Embedded in Magnesium Silicate Hollow Spheres for Multi-Color Display

Zhao Zhenfu1*, Wu Zhihai1, Cheng Jiong1, Jing Liang2, Hou Yafei1*

1

The Department of Microelectronics Science and Engineering, Science Faculty,

Ningbo University 2

Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Science,

Beijing 100083, China Address correspondence to [email protected], [email protected]

ABSTRACT Organometal halide perovskite quantum dots (PQDs) have recently received much attention as a very promising family of materials with excellent performance in electronic and optoelectronic fields, but these perspectives are being restrained by the severe stability, such as chemical and optical degradations. Herein, we propose and demonstrate a facile solution synthesis of nanocomposites of CH3NH3PbX3 (X= Cl, Br, I) PQDs embedded in magnesium silicate hollow spheres. The resultant nanocomposites preserved the strong photoluminescence of the CH3NH3PbX3 PQDs and the emission peak can be tunable from blue to red region. Photo-stability tests demonstrated that the nanocomposites samples were obviously more stable than the bare CH3NH3PbX3 PQDs. The photoluminescence (PL) of the nanocomposites sample still kept at 80% after 72 h UV LED illumination, which was much higher than the remnant PL (30%) of the pure CH3NH3PbX3 PQDs. With their high thermal

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2 stability and photo-stability, we demonstrated that these nanocomposites can be used as phosphors in an on-chip UV LED for multi-color display. It offers a facile method to protect perovskite quantum dots and may have great potential applications in solid-state lighting systems with demand of high color quality such as lasers, displays, and light emitting diodes.

INTRODUCTION Recently, organometal halide perovskites quantum dots (PQDs) or nanocrystals have attracted much attention due to their excellent optical properties such as high photoluminescence quantum yields (PLQYs), color-tunable, narrow-band emissions, and short radiative lifetimes.1-3 As a novel emerging optoelectronic material, organometal halide PQDs or nanocrystals have been of great interest in many applications e.g. light-emitting diodes (LED),4,5 low-threshold laser,6 photo-detection,7 solar cell8 and colorful display.9 Compared to classical Cd-based chalcogenide QDs, organometal halide PQDs could be completed with much lower temperatures and simpler procedures. Despite the merits of the organometal halide PQDs, the stability and photoluminescence quantum yield of organometal halide PQDs are easily susceptible to natural environmental factors including humidity, temperature, and oxygen. Especially, iodide-substituted PQDs with light emissions in the red and near-infrared regions are easily destroyed in the open air.10 These shortcomings limit their practical applications. Currently, several groups have made great progress in solving this problem,


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3 especially for all-inorganic PQDs (CsPbX3). There are often two methods adopted to protect PQDs from corrosions, oxidations or other chemical attacks. One way is to coat PQDs with transparent inorganic materials (such as alumina (Al2O3),11 silica oxide (SiO2),12 ZnS13) or polymer (trioctylphosphine oxide,14 alkyl phosphate15). The other is to embed PQDs into transparent material matrixes (e.g. polystyrene beads matrixes,16,

17

silicone resins,18 ammonium bromide framework,19 and mesoporous

silica matrixes20). For example, Chen, X et al. reported that embedding lead halide PQDs into carboxybenzene micro-crystals could improve their stability.21 Veldhuis, S.A el al. employed benzyl alcohol to treat CH3NH3PbBr3 nanocrystals, result in high luminescence, stability, and ultralow amplified spontaneous emission thresholds.6 Wang, H. et al. prepared nanocomposites of organometal halide perovskite nanocrystals embedded in silicone resins, which exhibited enhanced stability and luminescence.18 G. L. Yang et al also demonstrated that the MAPbBr3/NaNO3 nanocomposites by embedding perovskites into ionic matrices exhibited improved thermal and photo-stability.22 However, most of them are focusing in coating PQDs with polymer which is not suitable for high temperature environment applications. Moreover, most coating process is complicated and should be completed in glove box (oxygen free and water free). Transparent inorganic materials such as SiO2 or Al2O3, the encapsulation process for PQDs need trance water in toluene (analytical grade, H2O content 0.0184%) or exposed long time in the open air with relative high humidity which is very fatal for iodide-substituted PQDs.11,

12

Therefore, the

development of a simple method of embedding or coating perovskite QDs with



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4 transparent inorganic materials and not destroying their PL is still a very challenging work. As a transparent and eco-friendly inorganic material, magnesium silicate possesses unique structure, and good thermal stability. Especially magnesium silicate hollow spheres with porous structure and large specific surface areas have great potential application in many fields, such as absorbents in water purity,23, 24 drug deliveries,25 luminescence sensor.26 Here, we describe a simple strategy that incorporates CH3NH3PbX3 (MAPbX3) PQDs into magnesium silicate hollow spheres (MSHSs) in toluene via a modified ligand-assisted reprecipitation method at ambient condition. The whole process is very simple and can be operated in the open air. The major finding is that these nanocomposites of MAPbX3 PQDs embedded in magnesium silicate hollow spheres (MAPbX3 QDs-MSHSs) preserved outstanding PL, with emission peaks broadly tunable in the blue to red region and high quantum yields (QY) of above 50%. These nanocomposites have surprising high thermal stability and high photo-stability, which are demonstrated as phosphor for multi-color lighting. EXPERIMENTAL METHODS Materials. All reagents were here used without further purification: PbCl2 (lead (II) chloride, 99%, Aladdin), PbBr2 (lead (II) bromide 99%, Aladdin), PbI2 (lead (II) iodide 98.5%, Aladdin), octylamine (99%, Aladdin), N, N-dimethylformamide (analytical grade, Aladdin), dimethylsulfoxide (DMSO, analytical grade, Aladdin), toluene (analytical grade, Bei Jing Chemical Reagent Co., Ltd., China). CH3NH3Cl (MACl), CH3NH3Br (MABr), and CH3NH3I (MAI) were purchased from Xi’an


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5 Polymer Light Technology Corp. Hexahydrated magnesium chloride (MgCl2.6H2O), ammonium chloride (NH4Cl), ammonia water (NH3.H2O), tetraethylorthosilicate (TEOS)were purchased from Shanghai Macklin biochemical Co., Ltd.

Synthesis of magnesium silicate hollow spheres (MSHSs). Magnesium silicate hollow spheres were fabricated using SiO2 spheres as chemical template via hydrothermal approach. Typically, 1 mmol MgCl2.6H2O (0.203 g) and 10 mmol ammonia chloride were dissolved in 30 mL deionized water, followed by the addition of 1 mL ammonia aqueous solution (28 wt.%). 0.1g SiO2 spheres were dispersed homogeneously in 20 mL deionized water. After the above two solutions were mixed until homogeneous and transferred into a 100 mL Teflon autoclave heated at 140 °C for 12 h. The resulting white samples were washed several times with ethanol and deionized water. Finally, the MSHSs were achieved after dried in vacuum at 60 °C for 12 h.

Synthesis of MAPbX3 PQDs. For the synthesis of CH3NH3PbBr3 (MAPbBr3) PQDs, 0.4 mmol (44.8 mg) methylamine bromide (CH3NH3Br) and 0.3 mmol (110 mg) lead bromide (PbBr2) were dissolved in 1 mL of anhydrous DMF and 17 mL of γ-butyrolactone mixed solution with 40 µL of octylamine to form a halide perovskite precursor solution. Next, 1 mL of the perovskite precursor solution was dropped into 20 mL of toluene with vigorous stirring. The colloidal solution was centrifuged at 8000 rpm for 5 min to discard the aggregated precipitates, and the perovskite QDs were obtained after being centrifuged at 15000 rpm. CH3NH3PbBr1.5Cl1.5 QDs or CH3NH3PbBr1.5I1.5 QDs was fabricated by a similar method with blending the



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6 perovskite precursor solution with an appropriate ratio. Dimethylsulfoxide and γ-butyrolactone mixed solution was used to dissolve the PbCl2 and CH3NH3Cl.

Synthesis of MAPbX3 QDs-MSHSs nanocomposites. For the synthesis of nanocomposites of CH3NH3PbBr3 (MAPbBr3) PQDs embedded in MSHSs, 0.4 mmol (44.8 mg) methylamine bromide (CH3NH3Br) and 0.3 mmol (110 mg) lead bromide (PbBr2) were dissolved in 1 mL of anhydrous DMF and 17 mL of γ-butyrolactone mixed solution with 30 µL of octylamine to form a halide perovskite precursor solution. Next, 0.1 g MSHSs were dispersed homogeneously in 100 mL toluene. Then, 6 mL of the perovskite precursor solution was dropped into 100 mL of above toluene with vigorous stirring for 4 h. After that, the colloidal solution was centrifuged at 7000 rpm for 5 min to collect the MAPbBr3 QDs-MSHSs nanocomposites. The nanocomposites

of

CH3NH3PbBr1.5Cl1.5 QDs-MSHSs

or

CH3NH3PbBr1.5I1.5

QDs-MSHSs were fabricated by a similar method with blending the perovskite precursor solution with an appropriate ratio. Dimethylsulfoxide and γ-butyrolactone mixed solution was used to dissolve the PbCl2 and CH3NH3Cl.

LED encapsulation. In this procedure, 20 mg blue, green, red MAPbX3 QDs-MSHSs nanocomposites were mixed with 0.5 g of silicone resin B, respectively. The resulting mixture was then heated to 40 °C for 1 h to remove the solvent. A half equal of silicone resin A (0.25 g) were mixed with the previously prepared silicone resin B mixture. After bubbles were removed, the mixture was dropped onto a UV chip and then thermally cured for 2 h at 60 °C in an oven.

Characterizations. The structure and morphology of as-grown samples was


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7 characterized using XRD (Bruker D8 Advanced diffractometer with Cu Kα radiation) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SU8020). UV−Vis absorption was measured on a LAMBDA950 UV/Vis/NIR spectrophotometer, and PL spectra were taken using a fluorescence spectrometer (Cary Eclipse). The absolute PL quantum efficiency was measured by a fluorescence spectrometer with an integrated sphere excited under the 405 nm laser irradiation. The PL decay curves were collected with an all-functional steady-state/transient fluorescence spectrometer (EI/FLS980-S2S2-stm). The electroluminescence spectra of LED were measured using a using an integrating sphere with an analyzer system (PR705 spectrometer).

RESULTS AND DISCUSSION The X-ray diffraction (XRD) patterns of pure magnesium silicate spheres (MSHSs) and MAPbX3 QDs-MSHSs nanocomposites are shown in Figure 1. Pure MSHSs has mainly three peaks at 2θ = 20°, 35°, 60° corresponding to its (020), (200) and (332) plane, respectively, which is similar to other reports.23 The XRD pattern peaks of MAPbBr3 QDs at 15.5°, 21.1°, 30.1°, 33.7°, 43.03°, and 45.9° correspond respectively to the reflections from (100), (110), (200), (210), (220), and (300) crystal planes of a cubic phase structure (ICSD:252415), while the XRD peaks of red MAPbBr1.5I1.5 QDs-MSHSs nanocomposites move to smaller angles comparing to those of the green or blue one because of the relative large radius of iodine anion.27 X-ray diffraction measurements confirm that magnesium silicate and the perovskite



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8 phase exist in the nanocompositions.

Figure 1. X-ray diffraction patterns of magnesium silicate spheres (MSHSs), MAPbCl1.5Br1.5 QDs-MSHSs, MAPbBr3 QDs-MSHSs, MAPbBr1.5I1.5 QDs-MSHSs, respectively.

The morphology of the as-prepared MSHSs and MAPbBr3 QDs-MSHSs nanocomposites were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). As shown in Figure 2, the final MSHSs were composed of large uniform, spherical particles, and the surface of the spherical particles is rough, porous, and covered with a lot of thin lamellae (see Fig S1). Comparing to the pure MSHSs, MAPbBr3 QDs-MSHSs nanocomposites still keep the spherical shape, but the surface of the spherical particles is more compact and this is because there are many MAPbBr3 PQDs that are filled in the space between magnesium silicate thin lamellae (see Fig. 2c, 2d and Fig. S4). MAPbBr1.5Cl1.5


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9 QDs-MSHSs and MAPbBr1.5I1.5 QDs-MSHSs have the similar morphology with that of MAPbBr3 QDs-MSHSs (see Fig S2). EDX composition mapping for O, Mg, Si, Pb and Br elements of MAPbBr3 QDs-MSHSs nanocomposites are presented in Fig. 2e. O, Mg, Si, Pb and Br elements are distributed in the whole area in accordance with the shape of the examined nanocomposite. These results confirmed that MAPbBr3 PQDs were successfully embedded into the magnesium silicate hollow spheres matrixes.



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10

Figure 2. (a) SEM photograph of magnesium silicate hollow spheres (MSHSs). (b) SEM photograph of MAPbBr3 QDs-MSHSs nanocomposites. TEM (c) and HRTEM (d) photograph of MAPbBr3 QDs-MSHSs nanocomposites. (e) EDX composition mapping for O, Mg, Si, Pb and Br element of MAPbBr3 QDs-MSHSs nanocomposites.


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11 Our simple method for synthesizing MAPbX3 QDs-MSHSs nanocomposites can be available to tune the optical absorption and emission spectra via controlling the ratio of the halides in the mixed PQDs. As shown in Figure 3, the PL peaks (and FWHM) of the as-prepared blue, green, and red MAPbX3 QDs were found at 462 nm (22 nm), 511 nm (25 nm), and 655 nm (36 nm), respectively. However, the PL peaks (and FWHM) of their corresponding MAPbX3 QDs-MSHSs nanocomposites were located in 466 nm (23 nm), 519 nm (24), 665 nm (37 nm), which are red-shifted comparing with their pure perovskite QDs (see Table S1). This is because the diameter of perovskite quantum dots embedded in magnesium silicate hollow spheres is a little larger than that of perovskite quantum dots (see Fig. S3). Figure 3c is the digital image of MAPbX3 QDs and their MAPbX3 QDs-MSHSs nanocomposites in toluene under ambient light and UV lamp with light emission blue, green, red (RGB) color, respectively. The absolute PL quantum yields (PLQYs) of blue MAPbCl1.5Br1.5 QDs-MSHSs, green MAPbBr3 QDs-MSHSs and red MAPbBr1.5I1.5 QDs-MSHSs are measured with an excitation of 405 nm, and the high values of 61%, 82%, 52% are obtained, respectively, as shown in table S1, which is comparable to that of the corresponding bare MAPbX3 QDs (see table S1). The high PLQYs indicated the reduction of nonradiative decay in the nanocomposites of MAPbX3 QDs-MSHSs. To understand the kinetics of electron-hole recombination in the MAPbX3 QDs and MAPbX3 QDs-MSHSs samples, the time-resolved PL spectra of these samples were measured, as shown in Figure 4. The curve can be well fitted with a double-exponential decay model, in which the PL lifetimes are considered as the



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12 summation of a short-lived lifetime (τ1) and a long-lived lifetime (τ2).28 The obtained short-lived PL lifetime of MAPbBr3 QDs-MSHSs nanocomposites is 0.86 ns with a percentage of 72%, which corresponds to the radiative recombination of the electron-hole pairs. The long-lived PL lifetime (τ2 =7.13) with a percentage of 28% is assigned to the surface state-related nonradiative recombination.12 The average PL decay lifetimes were 6.05, 5.9, and 7.43 ns for blue, green and red PQD-MSHSs nanocomposites, respectively, as shown in table S2. All samples showed a much shorter average lifetime (τav) than did bulk perovskite films (∼100 ns);29 the reduction in lifetime indicates that PL decay of perovskite QDs mainly dominated by geminate electron-hole recombination and electron-hole overlap, rather than the trap-assisted recombination at QDs boundaries.4

Figure 3. PL spectra (a) and optical absorption (b) of MAPbX3 QDs and MAPbX3 QDs-MSHSs nanocomposites with different halides components. (c) Digital image of perovskite QDs and MAPbX3 QDs-MSHSs nanocomposites colloidal solutions in toluene under ambient light and UV lamp with light emission.


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13

Figure 4. PL lifetime curves of bare MAPbX3 QDs and MAPbX3 QDs-MSHSs nanocomposites with different halides components.

Photo-stability, thermal stability and moisture resistant of PQDs are the key parameters for their practical applications. A photo-stability test of MAPbX3 QDs and their corresponding nanocomposites was carried out under continuous UV-light (380 nm, 5 W) irradiation. The test period was from 0 h to 72 h. MAPbX3 PQDs and MAPbX3 QDs–MSHSs were dispersed in toluene and exposed to UV light irradiation for 72 h. After 72 h, the relative PL intensity of MAPbX3 QDs was decreased to 30% (see Figure S5). From the reported core/shell structures of QDs, a passivation shell can prevent photo-oxidation during UV light irradiation

12, 21

. However, bare PQDs

only have a core structure, which is easily exposed to oxygen and thus causes surface



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14 defects. The relative PL intensity decreased quickly owing to surface defects and PQDs decomposed. For MAPbX3 QDs-MSHSs, the magnesium silicate hollow spheres can act as the protective matrixes for the MAPbX3 PQDs. After 72 h, the relative PL of MAPbX3 QDs-MSHSs still preserves about 80% under UV light irradiation, as shown in Figure 5a. We further used a thermal controller system to test the thermal stability of MAPbX3 QDs and their corresponding nanocomposites. The experimental temperature ranged from 10 °C to 100 °C. The relative PL intensity of MAPbX3 PQDs and their nanocomposites decreased when the temperature increased, as shown in Figure 5b. However, MAPbX3 QDs-MHSMs nanocomposites exhibited higher thermal stability than bare MAPbX3 PQDs. Especially for red MAPbBr1.5I1.5 QDs-MSHSs and blue MAPbBr3 QDs-MSHSs nanocomposites; the relative PL quantum yield still keeps 60%, when the temperature is up to 100 °C (see Figure S6). All in all, MAPbX3 QDs-MSHSs nanocomposites not only exhibit better photo stability but also high thermal-stability.


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15

Figure 5. Photo-stability test (a) and thermal stability test (b) of MAPbX3 QDs and MAPbX3 QDs-MSHSs, respectively. MAPbX3 perovskite quantum dots show outstanding PL properties, but are quite



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16 vulnerable to moisture, especially for iodide-substituted perovskite quantum dots. In order to evaluate the effect of moisture on the MAPbX3 QDs-MSHSs, we performed comparative studies of bare MAPbX3 perovskite QDs and MAPbX3 QDs-MSHSs that exposed to relative humidity (RH) of 40% and 90% for 12 h, as shown in Figure 6. When they are exposed to the low relative humidity (RH) of 40%, most of the samples maintained high quantum efficiency, except for the bare MAPbBr1.5I1.5 quantum dots. In comparison, they are exposed to the high relative humidity (RH) of 90%. The PLQYs of bare MAPbX3 perovskite QDs decrease more quickly than that of MAPbX3 QDs-MSHSs. The remaining PLQYs of bare MAPbX3 perovskite QDs were reduced to less than 10% after 12 h of moisture exposure, while MAPbX3 QDs-MSHSs retained high PLQYs of 62% for MAPbBr3 QDs-MSHSs, 37% for MAPbCl1.5Br1.5 QDs-MSHSs and 30% for MAPbBr1.5 I1.5 QDs-MSHSs at the same exposure time. The enhanced stability was attributed to the tight magnesium silicate thin lamellae matrixes of MSHSs, which protected the MAPbX3 PQDs from moisture.

Figure 6. Moisture test of MAPbX3 QDs, MAPbX3 QDs-MSHSs under relative humidity (RH) of 40% (a) and 90% (b) condition for 12 h of moisture exposure, respectively.


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17 PQDs are often used in color conversion and lighting because of their narrow emission spectra and high PLQYs that make them ideal materials for high-quality lighting applications.3,30 To explore the applications of MAPbX3 QDs-MSHSs nanocomposites in the full color lighting. A proof of concept multicolor LED was fabricated using a UV on-chip LED and a single-color conversion layer by directly mixing blue MAPbCl1.5Br1.5 QDs-MSHSs, green MAPbBr3 QDs-MSHSs and red MAPbBr1.5I1.5 QDs-MSHSs with silicone resin, respectively. The electroluminescent spectrums of blue MAPbCl1.5Br1.5 QDs-MSHSs, green MAPbBr3 QDs-MSHSs, and red MAPbBr1.5I1.5 QDs-MSHSs nanocomposites under the excitation of the UV chip (380 nm) are shown in Figure 7. The excitation emission wavelengths of blue, green and red nanocomposites were 466, 519 and 665 nm, respectively. Under continuous UV on-chip LED illumination, the EL spectra show little variation, which reveals a reasonable stability of the LED devices. The CIE color coordinates values of green nanocomposites (0.141, 0.08), blue nanocomposites (0.127, 0.745), and red nanocomposites (0.658, 0.29) covered a much larger are than the color space of the National Television Systems Committee standard with a matching rate of 92% (See Figure S7 and Table S1). The chromaticity is comparable with the performance of bare MAPbX3 QDs and previously reported CdSe QD-based LED.3, 31 These results demonstrated that MAPbX3 QDs-MSHSs nanocomposites have great potential application in wide color gamut display devices.



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18

Figure 7. The spectrums of blue (a), green (b), and red (c) MAPbX3 QDs-MSHSs nanocomposites was under the excitation of a 380 nm UV on-chip LED for continuous working eight hours. The following optical images are the corresponding glow color.

CONCLUSIONS In summary, we reported a simple method to prepare highly luminescent and ultra-stable MAPbX3 QDs-MSHSs nanocomposites via a modified ligand-assisted reprecipitation method in the open air. The resultant MAPbX3 QDs-MSHSs samples showed excellent optical properties, such as high PLQYs and emission peaks broadly tunable in the blue to red region. Compared to the bare MAPbX3 QDs, the MAPbX3 QDs-MSHSs exhibited much superior photo-stability, thermal stability and moisture resistant because the magnesium silicate thin lamellae acted as robust protective layer to prevent the MAPbX3 QDs from the attack of oxygen and moisture. A multi-color LED was designed by mixing blue MAPbX3 QDs-MSHSs, green MAPbX3


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19 QDs-MSHSs, and red MAPbX3 QDs-MSHSs with silicon resin, respectively and subjected to excitation by using a UV GaN chip. We provide a simple method of protecting PQDs and may enable applications in solid-state lighting systems with high color quality requirements such as displays, light emitting diodes and lasers. ACKNOWLEDGMENTS This work was supported by National Science Foundation of China (Grant No.11704206), Natural Science Foundation of Zhejiang Province (Grant No. LQ18A040001), Research Fund Project of Ningbo University (Grant No. XYL18019) and also sponsored by K.C. Wong Magna Fund in Ningbo University. Supporting Information The Supporting Information is available free of charge on the ACS Publications website. SEM

photograph

of

magnesium

silicate

hollow

spheres

(MSHSs),

MAPbCl1.5Br1.5 PQDs-MSHSs nanocomposites and MAPbBr1.5I1.5 PQDs-MSHSs nanocomposites. TEM image of magnesium silicate hollow spheres (MSHSs), MAPbBr3 PQDs and MAPbBr3 PQDs-MSHSs. CIE color coordinates corresponding to the MAPbX3 PQDs and MAPbX3 PQDs-MSHSs nanocomposites. PL quantum yields (PLQYs), emission peak (nm), FWHM (nm), CIE coordinates (x, y) for MAPbX3 PQDs and their corresponding nanocomposites of MAPbX3 PQDs-MSHSs with different halides components. The fitting parameters of the decay curve for MAPbX3 PQDs and their corresponding nanocomposites of MAPbX3 PQDs-MSHSs with different halides components. PL spectrum of bare MAPbX3 PQDs and MAPbX3



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20 PQDs-MSHSs nanocomposites exposed continuous UV-light (380 nm, 5 W) irradiation. PL spectrum of bare MAPbX3 PQDs and MAPbX3 PQDs-MSHSs nanocomposites undergo different temperature. REFERENCES (1) Schmidt, L. C.; Pertegas, A.; Gonzalez-Carrero, S.; Malinkiewicz, O.; Agouram, S.; Espallargas, G. M.; Bolink, H. J.; Galian, R. E.; Perez-Prieto, J., Nontemplate Synthesis of CH3NH3PbBr3 Perovskite Nanoparticles. J. Am. Chem. Soc. 2014, 136, 850-853. (2) Huang, H.; Susha, A. S.; Kershaw, S. V.; Hung, T. F.; Rogach, A. L., Control of Emission Color of High Quantum Yield CH3NH3PbBr3 Perovskite Quantum Dots by Precipitation Temperature. Adv. Sci. 2015, 2, 581-583. (3) Zhang, F.; Zhong, H.; Chen, C.; Wu, X. G.; Hu, X.; Huang, H.; Han, J.; Zou, B.; Dong, Y., Brightly Luminescent and Color-Tunable Colloidal CH3NH3PbX3 (X = Br, I, Cl) Quantum Dots: Potential Alternatives for Display Technology. ACS Nano 2015, 9, 4533-4542. (4) Kim, Y. H.; Wolf, C.; Kim, Y. T.; Cho, H.; Kwon, W.; Do, S.; Sadhanala, A.; Chan, G. P.; Rhee, S. W.; Sang, H. I., Highly Efficient Light-Emitting Diodes of Colloidal Metal-Halide Perovskite Nanocrystals beyond Quantum Size. ACS Nano 2017, 11, 6586-6593. (5) Liu, P.; Chen, W.; Wang, W.; Xu, B.; Wu, D.; Hao, J.; Cao, W.; Fang, F.; Li, Y.; Zeng, Y., Halide-Rich Synthesized Cesium Lead Bromide Perovskite Nanocrystals for Light-Emitting Diodes with Improved Performance. Chem. Mater. 2017, 29,


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TOC Graphic


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Figure 1. X-ray diffraction patterns of magnesium silicate spheres (MSHSs), MAPbCl1.5Br1.5 QDs-MSHSs, MAPbBr3 QDs-MSHSs, MAPbBr1.5I1.5 QDs-MSHSs, respectively. 181x110mm (300 x 300 DPI)



Figure 2. (a) SEM photograph of magnesium silicate hollow spheres (MSHSs). (b) SEM photograph of MAPbBr3 QDs-MSHSs nanocomposites. TEM (c) and HRTEM (d) photograph of MAPbBr3 QDs-MSHSs nanocomposites. (e) EDX composition mapping for O, Mg, Si, Pb and Br element of MAPbBr3 QDs-MSHSs nanocomposites. 472x555mm (300 x 300 DPI)


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PL spectra (a) and optical absorption (b) of MAPbX3 QDs and MAPbX3 QDs-MSHSs nanocomposites with different halides components. (c) Digital image of perovskite QDs and MAPbX3 QDs-MSHSs nanocomposites colloidal solutions in toluene under ambient light and UV lamp with light emission. 375x205mm (300 x 300 DPI)



PL lifetime curves of bare MAPbX3 QDs and MAPbX3 QDs-MSHSs nanocomposites with different halides components. 232x176mm (300 x 300 DPI)


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Photo-stability test (a) and thermal stability test (b) of MAPbX3 QDs and MAPbX3 QDs-MSHSs, respectively. 184x268mm (300 x 300 DPI)



Figure 7. The spectrums of blue (a), green (b), and red (c) MAPbX3 QDs-MSHSs nanocomposites was under the excitation of a 380 nm UV on-chip LED for continuous working eight hours. The following optical images are the corresponding glow color. 645x355mm (300 x 300 DPI)


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Nanocomposites of Perovskite Quantum Dots Embedded in

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