- Email: [email protected]
Suitable medium for CsPbBr3 quantum dots toward light-emitting-diodes fabrication
Accepted Manuscript Suitable Medium for CsPbBr3 Quantum Dots Toward Light-Emitting-Diodes Fabrication Rongrong Yuan, Ling Ding, Guangzhan Shao, Zelong Zhang, Jianming Liu, Weidong Xiang, Xiaojuan Liang PII: DOI: Reference:
S0167-577X(18)31441-1 https://doi.org/10.1016/j.matlet.2018.09.065 MLBLUE 24933
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
1 August 2018 7 September 2018 12 September 2018
Please cite this article as: R. Yuan, L. Ding, G. Shao, Z. Zhang, J. Liu, W. Xiang, X. Liang, Suitable Medium for CsPbBr3 Quantum Dots Toward Light-Emitting-Diodes Fabrication, Materials Letters (2018), doi: https://doi.org/ 10.1016/j.matlet.2018.09.065
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Suitable Medium for CsPbBr3 Quantum Dots Toward Light-Emitting-Diodes Fabrication
Rongrong Yuan, Ling Ding,Guangzhan Shao, Zelong Zhang, Jianming Liu, Weidong Xiang* and Xiaojuan Liang* College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China Abstract: To research optical properties of materials for light-emitting-diodes (LEDs) fabrication, CsPbBr3 quantum dots (QDs) were dispersed in five different substrates to investigate their luminescence. The results show that CsPbBr3 QDs embedded in glass matrices have superior stability, however, the QDs could not be evenly distributed in the matrices, which resulted in uneven luminescence of the glass. To solve this problem, epoxy resin was introduced as cladding material, which yielded a product that had good stability and consistency. CsPbBr3 QDs embedded in epoxy resin show great potential for green fluorescent components in LED applications.
Keywords: Ceramics; Luminescence; Nanosize
1. Introduction
CsPbX3 quantum dots (QDs) are promising materials with excellent properties, such as being bright and having tunable photoluminescence, a narrow emission spectrum, the emission wavelength of size effect, and high luminous efficiency [1-4]. Given its huge potential in many fields, researchers working in the areas of light-emitting diodes [57], laser polarizers [8], polarizers [10-11], solar cells [12-13], and photoelectric detectors[14] have expressed interest in CsPbX3 QD materials. The biggest problem with many materials used in this research is their poor stability in air. Additionally, solvents used to disperse QDs are volatile and have adverse effects on the environment and the human body. CsPbBr3 QDs are a widely studied form of green fluorescence, which possess a considerable quantum yield (QY). In 2015, Kovalenko et al. prepared a series of CsPbX3 nanocrystal solutions with a wider color gamut. The highest QY of CsPbBr3 nanocrystal solutions has reach up to 90% [15]. Fully inorganic CsPbBr3 perovskite QDs films were successfully fabricated as green-emitting luminescent materials for white-light generation by Song et al. in 2016, and the absolute photoluminescence quantum yield (PLQY) was measured to be 37.2%. To maintain a high degree of green luminescence in CsPbBr3 QDs, a nanocomposite was prepared by a simple and effective method in 2017 by Di et al. [16]. In the same year, a series of CsPbBr3 QD zinc borosilicate glass were fabricated successfully by Xiang et al., who studied the concentration of QDs embedded in glass matrices. Using this fabrication method,
1
the QY of CsPbBr3 QDs was enhanced to 84.5% [17]. Although the problem of stability has been resolved, uneven luminosity problems still exist. In the same CsPbBr3 QD zinc borosilicate glass, the light was strong where the QDs were accumulated. However, light emittance was weak where they scattered sparsely. Additionally, the surface of the prepared glass possessed many holes, which can increase the possibility of air and water corroding the glass. To solve this problem, we turned the prepared glass into powder that glowed evenly, then fixed it with epoxy resin to create a more perfect luminescent material.
2. Experimental
The single-dispersed CsPbBr3 QDs solution was synthesized by thermal injection method. 20 ml of methyl methacrylate (MMA) and 0.002 g benzoyl peroxide mixture were chosen as primary clad materials. The as-obtained CsPbBr3 solution was poured into mesoporous silica, after well mix and dry, and the luminescent powder was prepared successfully. CsPbBr3 glass was fabricated through melting and heat treatment methods. Then the glass was ground into fine powder, the finely ground powder were put into epoxy resin at last. Please see supplementary materials for detailed steps. 3. Results and discussion
The excitation spectra were first measured to obtain the optimal excitation conditions. It found that 365 nm was within the effective excitation wavelength range. Therefore, the PL spectra were all measured under the excitation of 365 nm. CsPbBr3 QDs were dispersed into different matrices having different emission wavelengths in the PL spectra, which is closely related to the sizes effect. The relative PL intensity values are shown in Figure 1a-e. QDs embedded in glass and epoxy resin show superior stability, and the difference is that the dispersed QD glass powders in the ethoxy resin have a more uniform luminescence than the QDs embedded in the bare glass.The X-ray diffraction (XRD) patterns are shown in Figure 1f. The CsPbBr3 QDs that are dispersed in n-hexane solution, SiO2, and glass matrix all possess sharp peaks in the XRD pattern. The sharper the peak, the better the crystallinity. CsPbBr3 QDs scattered in n-hexane solution showed intense sharp peaks due to the QDs being completely exposed to the solution. Each crystal face was completely detected, and the exposed QDs in the n-hexane solution possessed several sharp peaks located at approximately 15.11°, 21.86°, 30.81°, 34.65°, 37.92°, and 44.11°, corresponding to the (100), (110), (200), (211), and (202) planes, respectively, of the cubic phase of CsPbBr3 (JCPDS No. 54-0752).
2
When CsPbBr3 QDs are dispersed in SiO2 and zinc borosilicate glass, the sharp peaks are broadened, which is attributed to the CsPbBr3 QDs being partially encased in the matrix. Notably, CsPbBr 3 QDs dispersed in PMMA and epoxy resin has none peaks, indicating that the CsPbBr3 QDs are been completely covered. The optical images of the samples also indicate that CsPbBr3 QDs embedded in epoxy resin had the best luminous performance. The CsPbBr3 QDs dispersed in a n-hexane solution containing many particles having an average size of 10 nm (Figure 2a), the PL emission peak was determined at 523 nm. When PMMA and QDs interact, QDs with a small size (average size of 6.06 nm) are absorbed preferentially (Figure 2b). After adsorption saturation, the reaction between QDs and PMMA is complete. Consequently, the CsPbBr3 QDs dispersed in PMMA have a short emission peak at 513 nm. Similarly, when QDs are incorporated into mesoporous SiO 2, QDs with the same size as the aperture are priority to enter , with a size of approximately 3-9 nm (Figure 2c). When the pores are full, QDs no longer have the opportunity to embedded in the hole, which results in a shorter-wavelength emission peak than obtained for its distribution in solution. In contrast, QDs embedded in glass matrices have a longer-wavelength emission peak, which is determined by the different formation behavior. Glass is typically prepared in two steps. The first step is to formulate the crystal seed. The second step is to provide suitable conditions for the growth of the seed. In this process, the temperature and time during heat treatment have a great influence on the growth of the crystal seed. Under the temperature of 520℃, and the heat treatment time controlled to within 10 h, , the size of QDs are distributed to within 8-16 nm (Figure 2d). When the glass powders are further dissolved in epoxy resin, the size of the QDs shows little change (Figure 2e). Hence, their luminescence is the same as that of the glass. The QY of five materials were measured. QDs dispersed in n-hexane solution possessed the highest QY of 129 %. The QY of QDs embedded in SiO2 and glass were estimated to be 85% and 73%, respectively. The considerable QY indicates that CsPbBr3 QD is a promising luminescent material. The relevant data are listed in Table 1. To further investigate their potential application for LEDs, we performed the following: Firstly, CsPbBr3 QD glass powder and Sr2Si5N8:Eu2+ phosphors were embedded in epoxy resin, and fabricated into several thin films. The images of the green and red films are shown in Figure 3a. Then, LED devices were constructed by combining a blue GaN chip with the green-emitting CsPbBr3 QDs film and commercial red-emitting Sr2Si5N8:Eu2+ film. We measured the EL spectra of the as-prepared LED device at a driving current of 20 mA, as shown in Figure 3b-d. The EL spectra show broad emission bands, with an emission band at 460 nm, which is attributed to the GaN blue chip; a narrow green emission band, which originated from the CsPbBr3 QD film; and a broad red emission band,
3
which is attributed to the Sr2Si5N8:Eu2+ film. Hence, CsPbBr3 QDs embedded in epoxy resin film are a promising candidate as a green color converter. The color stability parameters of this LED device are listed in Table S1. The correlated color temperature (CCT) decreased from 10118 K to 4339 K, and the CRI slightly increased slightly from 18.5 to 77.0, owing to the contribution of the Sr 2Si5N8:Eu2+ phosphors. 4. Conclusions
In summary, CsPbBr3 QDs were successfully embedded in five different matrices. The excellent luminescence of the materials demonstrates that the QDs can sustain a perfect crystal phase. The stability of the CsPbBr 3 QDs was improved by effectively preventing them from exposure to the external environment in the solid matrix. Moreover, the excellent performance of the LED device indicates that the as-prepared CsPbBr3 QD glass has immense potential in solid-state lighting applications. Acknowledgements
The work was financially supported by the National Natural Science Foundation of China (51672192). The authors declare that they have no conflicts of interest. References [1] G. Nedelcu, L. Protesescu, S. Yakunin, M. I. Bodnarchuk, M. J. Grotevent and S. Yakunin. Nano Letters. 15(2015) 5635-5640. [2] I. Lignos, S. Stavrakis, G. Nedelcu, L. Protesescu, A. J. deMello and M. V. Kovalenko, Nano Lett. 16(2016) 1869−1877. [3] S. Wei, Y. Yang, X. Kang, L. Wang, L. Huang and D. Pan. Chem. Commun. 52(2016)7265-7268. [4] F. Palazon, Q. A. Akkerman, M. Prato and L. Manna, ACS Nano. 10(2016)1224−1230. [5] G. R. Li, Z. K. Tan, D. W. Di, M. L. Lai, L. Jiang, J. H. Lim, R. H. Friend and N. C. Greenham. Nano Lett. 15(2015)2640−2644. [6] Y. Kim, H. Cho, J. H. Heo, T. Kim, N. Myoung, C. Lee, S. H. ImT. Lee. Adv. Mater. 27(2015)1248–1254. [7] J. Song, J. Li, X. Li, L. Xu, Y. Dong and H. Zeng. Adv. Mater. 27(2015)7162– 7167. [8] Y. Wang, X. Li, J. Song, L. Xiao and H. Zeng. Adv. Mater. 27(2015)7101-7108.
4
[9] S. Yakunin, L. Protesescu, F. Krieg, M. I. Bodnarchuk, G. Nedelcu, M. Humer, G. De Luca, M. Fiebig, W. Heiss and M. V. Kovalenko, Nat. commun. 6(2015)8056. [10] G. Nedelcu, L. Protesescu, S. Yakunin, M.I. Bodnarchuk, M.J. Grotevent and M.V. kovalenko. Nano Letters. 15(2015)5635-5640. [11] D. Wang, D. Wu, D. Dong, W. Chen, J. Hao, J. Qin, B. Xu, K. Wang and X. Sun. Nanoscale. 8(2016) 1156511570. [12] W. S. Yang, J. H. Noh, N. J. Jeon, Y. C. Kim, S. Ryu and J. Seo. Science. 348(2015),1234-1237. [13] A. Mei, X. Li, L. Liu, Z. Ku, T. Liu, Y. Rong, M. Xu, M. Hu, J. Chen, Y. Yang, M. Grätzel and H. Han. Science. 345(2014) 295–298. [14] L. Protesescu, S. Yakunin, M. I. Bodnarchuk, F. Bertolotti, N. Masciocchi, A. Guagliardi and M.V. Kovalenko. Chem. Soc. 138(2016)14202−14205. [15] L. Protesescu, S. Yakunin, M. I. Bodnarchuk, F. Krieg, R. Caputo, C. H. Hendon, R. X. Yang, A. Walsh and M. V. Kovalenko. Nano Lett. 15(2015)3692−3696. [16] X. Di, Z. Hu, J. Jiang, M. Hei, L. Zhou, W. Xiang and X. Juan. Dyes and Pigments. 146 (2017) 361-367. [17] R. Yuan, L. Shen, C. Shen, J. Liu, L. Zhou, W. Xiang and X. Liang. Chem. Commun. 54(2018) 3395-3398.
5
Graphical abstract
Figure 1. (a-e) PL spectra and excitation spectra of CsPbBr3 QDs dispersed in different matrix. (f) The XRD patterns of CsPbBr3 QDs dispersed in different matrix.
6
Figure 2. Size distribution of CsPbBr3 QDs embed in different matrix.
7
Fig 3(a) The picture of CsPbBr3 and commercial red Sr2Si5N8:Eu2+ ethoxyline resin films under natural light and 365 UV lamp. (b) EL spectra for as-fabricated LEDs based on blue chip, CsPbBr3 and commercial red Sr2Si5N8:Eu2+ ethoxyline resin films.
8
Table 1. Excitation wavelength, emission peak and QY of CsPbBr3 QDs dispersed in five different matrix. Samples
Size distribution
excitation
Emission peak
QY
solution
8-18 nm
365 nm
523 nm
129%
PMMA
-
365 nm
513 nm
-
SiO2
7-10 nm
365 nm
520 nm
85%
B-Zn-Si glasses
12-33 nm
365 nm
530 nm
73%
ethoxyline resin
-
365 nm
532 nm
-
9
Highlight · As an encapsulant, epoxy resins solve the stability problem of quantum dots compare to quantum dots in solvents. · As an encapsulant, epoxy resins solve the problem of non-uniform luminescence compare to quantum dots in PMMA, SiO2 and glass. · CsPbBr3 QDs in five different substrates has different luminescence is greatly related to the sizes effect.
10
S0167-577X(18)31441-1 https://doi.org/10.1016/j.matlet.2018.09.065 MLBLUE 24933
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
1 August 2018 7 September 2018 12 September 2018
Please cite this article as: R. Yuan, L. Ding, G. Shao, Z. Zhang, J. Liu, W. Xiang, X. Liang, Suitable Medium for CsPbBr3 Quantum Dots Toward Light-Emitting-Diodes Fabrication, Materials Letters (2018), doi: https://doi.org/ 10.1016/j.matlet.2018.09.065
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Suitable Medium for CsPbBr3 Quantum Dots Toward Light-Emitting-Diodes Fabrication
Rongrong Yuan, Ling Ding,Guangzhan Shao, Zelong Zhang, Jianming Liu, Weidong Xiang* and Xiaojuan Liang* College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China Abstract: To research optical properties of materials for light-emitting-diodes (LEDs) fabrication, CsPbBr3 quantum dots (QDs) were dispersed in five different substrates to investigate their luminescence. The results show that CsPbBr3 QDs embedded in glass matrices have superior stability, however, the QDs could not be evenly distributed in the matrices, which resulted in uneven luminescence of the glass. To solve this problem, epoxy resin was introduced as cladding material, which yielded a product that had good stability and consistency. CsPbBr3 QDs embedded in epoxy resin show great potential for green fluorescent components in LED applications.
Keywords: Ceramics; Luminescence; Nanosize
1. Introduction
CsPbX3 quantum dots (QDs) are promising materials with excellent properties, such as being bright and having tunable photoluminescence, a narrow emission spectrum, the emission wavelength of size effect, and high luminous efficiency [1-4]. Given its huge potential in many fields, researchers working in the areas of light-emitting diodes [57], laser polarizers [8], polarizers [10-11], solar cells [12-13], and photoelectric detectors[14] have expressed interest in CsPbX3 QD materials. The biggest problem with many materials used in this research is their poor stability in air. Additionally, solvents used to disperse QDs are volatile and have adverse effects on the environment and the human body. CsPbBr3 QDs are a widely studied form of green fluorescence, which possess a considerable quantum yield (QY). In 2015, Kovalenko et al. prepared a series of CsPbX3 nanocrystal solutions with a wider color gamut. The highest QY of CsPbBr3 nanocrystal solutions has reach up to 90% [15]. Fully inorganic CsPbBr3 perovskite QDs films were successfully fabricated as green-emitting luminescent materials for white-light generation by Song et al. in 2016, and the absolute photoluminescence quantum yield (PLQY) was measured to be 37.2%. To maintain a high degree of green luminescence in CsPbBr3 QDs, a nanocomposite was prepared by a simple and effective method in 2017 by Di et al. [16]. In the same year, a series of CsPbBr3 QD zinc borosilicate glass were fabricated successfully by Xiang et al., who studied the concentration of QDs embedded in glass matrices. Using this fabrication method,
1
the QY of CsPbBr3 QDs was enhanced to 84.5% [17]. Although the problem of stability has been resolved, uneven luminosity problems still exist. In the same CsPbBr3 QD zinc borosilicate glass, the light was strong where the QDs were accumulated. However, light emittance was weak where they scattered sparsely. Additionally, the surface of the prepared glass possessed many holes, which can increase the possibility of air and water corroding the glass. To solve this problem, we turned the prepared glass into powder that glowed evenly, then fixed it with epoxy resin to create a more perfect luminescent material.
2. Experimental
The single-dispersed CsPbBr3 QDs solution was synthesized by thermal injection method. 20 ml of methyl methacrylate (MMA) and 0.002 g benzoyl peroxide mixture were chosen as primary clad materials. The as-obtained CsPbBr3 solution was poured into mesoporous silica, after well mix and dry, and the luminescent powder was prepared successfully. CsPbBr3 glass was fabricated through melting and heat treatment methods. Then the glass was ground into fine powder, the finely ground powder were put into epoxy resin at last. Please see supplementary materials for detailed steps. 3. Results and discussion
The excitation spectra were first measured to obtain the optimal excitation conditions. It found that 365 nm was within the effective excitation wavelength range. Therefore, the PL spectra were all measured under the excitation of 365 nm. CsPbBr3 QDs were dispersed into different matrices having different emission wavelengths in the PL spectra, which is closely related to the sizes effect. The relative PL intensity values are shown in Figure 1a-e. QDs embedded in glass and epoxy resin show superior stability, and the difference is that the dispersed QD glass powders in the ethoxy resin have a more uniform luminescence than the QDs embedded in the bare glass.The X-ray diffraction (XRD) patterns are shown in Figure 1f. The CsPbBr3 QDs that are dispersed in n-hexane solution, SiO2, and glass matrix all possess sharp peaks in the XRD pattern. The sharper the peak, the better the crystallinity. CsPbBr3 QDs scattered in n-hexane solution showed intense sharp peaks due to the QDs being completely exposed to the solution. Each crystal face was completely detected, and the exposed QDs in the n-hexane solution possessed several sharp peaks located at approximately 15.11°, 21.86°, 30.81°, 34.65°, 37.92°, and 44.11°, corresponding to the (100), (110), (200), (211), and (202) planes, respectively, of the cubic phase of CsPbBr3 (JCPDS No. 54-0752).
2
When CsPbBr3 QDs are dispersed in SiO2 and zinc borosilicate glass, the sharp peaks are broadened, which is attributed to the CsPbBr3 QDs being partially encased in the matrix. Notably, CsPbBr 3 QDs dispersed in PMMA and epoxy resin has none peaks, indicating that the CsPbBr3 QDs are been completely covered. The optical images of the samples also indicate that CsPbBr3 QDs embedded in epoxy resin had the best luminous performance. The CsPbBr3 QDs dispersed in a n-hexane solution containing many particles having an average size of 10 nm (Figure 2a), the PL emission peak was determined at 523 nm. When PMMA and QDs interact, QDs with a small size (average size of 6.06 nm) are absorbed preferentially (Figure 2b). After adsorption saturation, the reaction between QDs and PMMA is complete. Consequently, the CsPbBr3 QDs dispersed in PMMA have a short emission peak at 513 nm. Similarly, when QDs are incorporated into mesoporous SiO 2, QDs with the same size as the aperture are priority to enter , with a size of approximately 3-9 nm (Figure 2c). When the pores are full, QDs no longer have the opportunity to embedded in the hole, which results in a shorter-wavelength emission peak than obtained for its distribution in solution. In contrast, QDs embedded in glass matrices have a longer-wavelength emission peak, which is determined by the different formation behavior. Glass is typically prepared in two steps. The first step is to formulate the crystal seed. The second step is to provide suitable conditions for the growth of the seed. In this process, the temperature and time during heat treatment have a great influence on the growth of the crystal seed. Under the temperature of 520℃, and the heat treatment time controlled to within 10 h, , the size of QDs are distributed to within 8-16 nm (Figure 2d). When the glass powders are further dissolved in epoxy resin, the size of the QDs shows little change (Figure 2e). Hence, their luminescence is the same as that of the glass. The QY of five materials were measured. QDs dispersed in n-hexane solution possessed the highest QY of 129 %. The QY of QDs embedded in SiO2 and glass were estimated to be 85% and 73%, respectively. The considerable QY indicates that CsPbBr3 QD is a promising luminescent material. The relevant data are listed in Table 1. To further investigate their potential application for LEDs, we performed the following: Firstly, CsPbBr3 QD glass powder and Sr2Si5N8:Eu2+ phosphors were embedded in epoxy resin, and fabricated into several thin films. The images of the green and red films are shown in Figure 3a. Then, LED devices were constructed by combining a blue GaN chip with the green-emitting CsPbBr3 QDs film and commercial red-emitting Sr2Si5N8:Eu2+ film. We measured the EL spectra of the as-prepared LED device at a driving current of 20 mA, as shown in Figure 3b-d. The EL spectra show broad emission bands, with an emission band at 460 nm, which is attributed to the GaN blue chip; a narrow green emission band, which originated from the CsPbBr3 QD film; and a broad red emission band,
3
which is attributed to the Sr2Si5N8:Eu2+ film. Hence, CsPbBr3 QDs embedded in epoxy resin film are a promising candidate as a green color converter. The color stability parameters of this LED device are listed in Table S1. The correlated color temperature (CCT) decreased from 10118 K to 4339 K, and the CRI slightly increased slightly from 18.5 to 77.0, owing to the contribution of the Sr 2Si5N8:Eu2+ phosphors. 4. Conclusions
In summary, CsPbBr3 QDs were successfully embedded in five different matrices. The excellent luminescence of the materials demonstrates that the QDs can sustain a perfect crystal phase. The stability of the CsPbBr 3 QDs was improved by effectively preventing them from exposure to the external environment in the solid matrix. Moreover, the excellent performance of the LED device indicates that the as-prepared CsPbBr3 QD glass has immense potential in solid-state lighting applications. Acknowledgements
The work was financially supported by the National Natural Science Foundation of China (51672192). The authors declare that they have no conflicts of interest. References [1] G. Nedelcu, L. Protesescu, S. Yakunin, M. I. Bodnarchuk, M. J. Grotevent and S. Yakunin. Nano Letters. 15(2015) 5635-5640. [2] I. Lignos, S. Stavrakis, G. Nedelcu, L. Protesescu, A. J. deMello and M. V. Kovalenko, Nano Lett. 16(2016) 1869−1877. [3] S. Wei, Y. Yang, X. Kang, L. Wang, L. Huang and D. Pan. Chem. Commun. 52(2016)7265-7268. [4] F. Palazon, Q. A. Akkerman, M. Prato and L. Manna, ACS Nano. 10(2016)1224−1230. [5] G. R. Li, Z. K. Tan, D. W. Di, M. L. Lai, L. Jiang, J. H. Lim, R. H. Friend and N. C. Greenham. Nano Lett. 15(2015)2640−2644. [6] Y. Kim, H. Cho, J. H. Heo, T. Kim, N. Myoung, C. Lee, S. H. ImT. Lee. Adv. Mater. 27(2015)1248–1254. [7] J. Song, J. Li, X. Li, L. Xu, Y. Dong and H. Zeng. Adv. Mater. 27(2015)7162– 7167. [8] Y. Wang, X. Li, J. Song, L. Xiao and H. Zeng. Adv. Mater. 27(2015)7101-7108.
4
[9] S. Yakunin, L. Protesescu, F. Krieg, M. I. Bodnarchuk, G. Nedelcu, M. Humer, G. De Luca, M. Fiebig, W. Heiss and M. V. Kovalenko, Nat. commun. 6(2015)8056. [10] G. Nedelcu, L. Protesescu, S. Yakunin, M.I. Bodnarchuk, M.J. Grotevent and M.V. kovalenko. Nano Letters. 15(2015)5635-5640. [11] D. Wang, D. Wu, D. Dong, W. Chen, J. Hao, J. Qin, B. Xu, K. Wang and X. Sun. Nanoscale. 8(2016) 1156511570. [12] W. S. Yang, J. H. Noh, N. J. Jeon, Y. C. Kim, S. Ryu and J. Seo. Science. 348(2015),1234-1237. [13] A. Mei, X. Li, L. Liu, Z. Ku, T. Liu, Y. Rong, M. Xu, M. Hu, J. Chen, Y. Yang, M. Grätzel and H. Han. Science. 345(2014) 295–298. [14] L. Protesescu, S. Yakunin, M. I. Bodnarchuk, F. Bertolotti, N. Masciocchi, A. Guagliardi and M.V. Kovalenko. Chem. Soc. 138(2016)14202−14205. [15] L. Protesescu, S. Yakunin, M. I. Bodnarchuk, F. Krieg, R. Caputo, C. H. Hendon, R. X. Yang, A. Walsh and M. V. Kovalenko. Nano Lett. 15(2015)3692−3696. [16] X. Di, Z. Hu, J. Jiang, M. Hei, L. Zhou, W. Xiang and X. Juan. Dyes and Pigments. 146 (2017) 361-367. [17] R. Yuan, L. Shen, C. Shen, J. Liu, L. Zhou, W. Xiang and X. Liang. Chem. Commun. 54(2018) 3395-3398.
5
Graphical abstract
Figure 1. (a-e) PL spectra and excitation spectra of CsPbBr3 QDs dispersed in different matrix. (f) The XRD patterns of CsPbBr3 QDs dispersed in different matrix.
6
Figure 2. Size distribution of CsPbBr3 QDs embed in different matrix.
7
Fig 3(a) The picture of CsPbBr3 and commercial red Sr2Si5N8:Eu2+ ethoxyline resin films under natural light and 365 UV lamp. (b) EL spectra for as-fabricated LEDs based on blue chip, CsPbBr3 and commercial red Sr2Si5N8:Eu2+ ethoxyline resin films.
8
Table 1. Excitation wavelength, emission peak and QY of CsPbBr3 QDs dispersed in five different matrix. Samples
Size distribution
excitation
Emission peak
QY
solution
8-18 nm
365 nm
523 nm
129%
PMMA
-
365 nm
513 nm
-
SiO2
7-10 nm
365 nm
520 nm
85%
B-Zn-Si glasses
12-33 nm
365 nm
530 nm
73%
ethoxyline resin
-
365 nm
532 nm
-
9
Highlight · As an encapsulant, epoxy resins solve the stability problem of quantum dots compare to quantum dots in solvents. · As an encapsulant, epoxy resins solve the problem of non-uniform luminescence compare to quantum dots in PMMA, SiO2 and glass. · CsPbBr3 QDs in five different substrates has different luminescence is greatly related to the sizes effect.
10