Discovery of the Crystal Phase Transition on Lead-free Cesium Manganese Bromine Perovskite Nanocrystal by Solvent Concentration

Discovery of the Crystal Phase Transition on Lead-free Cesium Manganese Bromine Perovskite Nanocrystal by Solvent Concentration | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Discovery of the Crystal Phase Transition on Lead-free Cesium Manganese Bromine Perovskite Nanocrystal by Solvent Concentration Tae Wook Kang, Eun Jin Choi, Young Ji Park, Jonghee Hwang, Byungseo Bae, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-805887/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract We have been demonstrated the crystal phase transition for lead-free cesium manganese bromine perovskite nanocrystal synthesized by the modified hot-injection method due to change the concentration of solvent (trioctylphosphine; TOP). The compositions to be synthesized were determined by the amount of TOP solvent, and the structure phase of nanocrystal was changed from hexagonal CsMnBr 3 to tetragonal Cs 3 MnBr 5 as the amount of TOP solvent increased. The emission peaks of CsMnBr 3 and Cs 3 MnBr 5 nanocrystals were observed at 650 nm (red) and 520 nm (green), respectively. After a durability test at 85 °C and 85% humidity for 24 h, the lead-free perovskite CsMnBr 3 nanocrystal powder maintained its initial emission intensity, and the metal halide Cs 3 MnBr 5 nanocrystal powder exhibited an increase in red emission due to the post-synthesis of CsMnBr 3 nanocrystals. Optical Materials and Devices CsMnBr3 perovskite nanocrystals Metal halide Cs3MnBr5 nanocrystal Phase-tunable synthesis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Lead halide perovskites, which have the general formula APbX 3 (where A = CH 3 NH 3 + (MA), HC(NH 2 ) 2 + (FA), or Cs + ; X = Cl, Br or I), has been studied since the middle of the 20th century [ 1 – 5 ]. Among these perovskites, inorganic cesium lead halide perovskite (Cs n PbX 2+n , X = Cl, Br, I, or a mixture thereof) nanocrystals have attracted significant attention as an optical material for display and lamp applications (e.g. color converter material), as an alternative to quantum dot materials. Within the past decade, there have been rapid advances in the synthesis of cesium lead halide perovskite nanocrystals for use in solar cells, light-emitting diodes (LEDs), lasers, and photodetectors because of the excellent optoelectronic performance of these perovskite nanocrystals [ 6 – 13 ]. They have interesting optical, excitonic, and charge-transport properties, including an outstanding photoluminescence quantum yield (PLQY) and tunable optical bandgap. Despite these advantages, however, the presence of Pb, a toxic element, in perovskite nanocrystals raises critical concerns with regard to commercialization. This is because the heavy metal Pb can affect human health and the environment [ 14 , 15 ]. The US EPA has set the maximum allowable content of Pb in air and water as 0.15 µg/L and 15 µg/L, respectively. The European Union regulates the use of heavy and toxic materials (including Pb) in electronic devices, and the use of lead-based technology is expected to decline in the future [ 16 , 17 ] Therefore, the development of a lead-free cesium halide perovskite that retains the outstanding properties of cesium lead halide nanocrystals is important, and several studies have been conducted recently in this regard. Metallic elements that have an electronic structure similar to that of Pb and can thus form stable perovskite structures—such as Sn, Sb, Bi, Eu, and Yb—have been considered as alternatives for Pb. Various lead-free halide perovskite nanocrystals, including those containing the aforementioned metal elements, have recently been developed and have achieved optoelectronic performance comparable to that of Pb-based counterparts [ 17 – 19 ]. These encouraging results obtained via exploration of lead-free perovskite nanocrystals indicate a major imminent breakthrough in the fabrication of new optoelectronic devices. In this study, to obtain lead-free inorganic halide perovskite nanocrystals, we focused on replacing Pb with the transition metal Mn. Mn has an ionic radius (0.083 nm for 6 coordination) similar to that of Pb (0.119 nm for 6 coordination), as well as a low toxicity, and has therefore attracted attention as a substitute for the B site in halide perovskites. Cesium manganese bromide perovskite nanocrystals, such as the red-emitting CsMnBr 3 and green-emitting Cs 3 MnBr 5 , have been reported to exhibit excellent optical properties [ 20 – 23 ]. In this paper, we synthesized red-emitting CsMnBr 3 and Cs 3 MnBr 5 perovskite nanocrystals using the modified hot-injection method and investigated the optical properties of these perovskite nanocrystals. Furthermore, we investigated the phase-tunable synthesis from Cs 3 MnBr 5 to CsMnBr 3 with controlling the amount of solvent. Results And Discussion Figure 1 shows the XRD patterns of the cesium manganese bromide perovskite nanocrystals with the amount of TOP solvent as well as the standard XRD patterns of the CsMnBr 3 and Cs 3 MnBr 5 from JCPDS card No. 26–0387 and No. 27–0117, respectively. The crystal structures of CsMnBr 3 and Cs 3 MnBr 5 are shown in Fig. 2 . The crystal structure of CsMnBr 3 consists of linear chains of distorted face-sharing [MnBr 6 ] octahedron with a D 3d symmetry parallel to the c-axis, that are bridged by Cs ions. Interestingly, the Mn − Mn distance is very short (~ 0.32982 nm) along the c-axis, leading to strongly coupled optical transitions. The XRD pattern of the sample prepared with 10 mL TOP solvent was indexed to the standard hexagonal CsMnBr 3 structure (JCPDS No. 26–0387); this sample contains the P6 3 /mmc (#194) space group and has lattice parameters a = b = 0.785878 nm and c = 0.659641 nm. In the crystal structure of Cs 3 MnBr 5 , the Mn 2+ ions are coordinated by four Br - ions to form a [MnBr 4 ] regular tetrahedron geometry with D 2d symmetry. The Mn 2+ site layers are separated by Cs + site layers in the direction of the c-axis, and the adjacent [MnBr 4 ] tetrahedrons maintain a distance of 0.780593(6) nm. The XRD pattern of the sample prepared with 20 mL TOP solvent corresponds to a single-phase tetragonal Cs 3 MnBr 5 structure (JCPDS No. 27–0117); this sample has the I4/mcm (#140) space group and lattice constants a = b = 0.992839 nm and c = 1.561187 nm. The nanocrystal samples prepared with 12.5 and 17.5 mL TOP solvent exhibit a mixed phase with hexagonal CsMnBr 3 and tetragonal Cs 3 MnBr 5 phases, and the phase transition of nanocrystal phase from CsMnBr 3 to Cs 3 MnBr 5 was observed as the amount of TOP solvent increased. The morphology of the synthesized nanocrystals with the amount of TOP solvent was analyzed using high-resolution TEM, as shown in Fig. 3 . The TEM images of lead-free perovskite CsMnBr 3 nanocrystals present a dispersed hexagonal morphology with an average size of ~ 20 nm. The interplanar spacing relative to the (021) crystalline planes of the CsMnBr 3 nanocrystals is about 0.3 nm. In contrast, the TEM image of Cs 3 MnBr 5 nanocrystals shows a dispersed tetragonal morphology with an average size of ~ 30 nm. The interplanar spacing relative to the (213) crystalline planes of the Cs 3 MnBr 5 nanocrystals is about 0.33 nm. The nanocrystals prepared with 12.5 and 17.5 mL TOP solvent coexist with the CsMnBr 3 and Cs 3 MnBr 5 nanocrystals; the compositional change between the CsMnBr 3 and Cs 3 MnBr 5 nanocrystals is determined by the amount of TOP solvent. Figure 4 presents the PL spectra of the obtained nanocrystals with the amount of TOP solvent. The inset images show the emission of the nanocrystals under irradiation with a 365 nm UV lamp; their color changes from red to green as the amount of TOP solvent increases from 10 to 20 mL. The emission spectrum of the lead-free perovskite CsMnBr 3 nanocrystals exhibits a broad red emission peak centered at 650 nm with a full-width-at-half-maximum (FWHM) of 95 nm. The red PL emission which assigned 4 T 1 → 6 A 1 transition in [MnBr 6 ] 4- octahedrons of the CsMnBr 3 nanocrystals is considered to be due to the relaxation from the lowest excited state to the ground state of Mn 2+ ions. This is consistent with reports of red emission from Mn 2+ in the MnBr 6 octahedron [ 24 , 25 ]. On the other hand, the emission spectrum of the Cs 3 MnBr 5 nanocrystals shows green emission at 520 nm with an FWHM of 50 nm. The strong green emission is ascribed to the metal-centered d–d transition of the Mn 2+ ion in the d 5 configuration with a [MnBr 4 ] tetrahedral coordination geometry [ 26 ]. Interestingly, the PL spectra of the Cs–Mn–Br nanocrystals can be controlled by simply changing the amount of TOP solvent, as depicted in Fig. 4 . With an increase of the amount of TOP solvent, the relative emission of red (CsMnBr 3 ) and green (Cs 3 MnBr 5 ) shifts toward green emission, implying that our study can achieve tunable the color between green and red by simply controlling the amount of TOP solvent. To evaluate the thermal and chemical stability of the CsMnBr 3 and Cs 3 MnBr 5 nanocrystals, a durability test was performed under high-temperature and high-humidity conditions of 85°C and 85%, respectively, for 24 h. The PL behaviors of the CsMnBr 3 and Cs 3 MnBr 5 nanocrystals after the durability test are shown in Fig. 5 (a). The lead-free perovskite CsMnBr 3 nanocrystal powder exhibits extremely high durability and maintains its initial PL intensity. In comparison, the PL intensity of the metal halide Cs 3 MnBr 5 nanocrystal powder does not decrease but rather increases in the red emission (CsMnBr 3 ) region. It is considered that the materials that remained unreacted during the preparation of the nanocrystals reacted to form more CsMnBr 3 nanocrystals due to the high temperature during the durability test. Both nanocrystals exhibited no change in the PL peak wavelength and FWHM values after the durability test. The structures of CsMnBr 3 and Cs 3 MnBr 5 are considered to have remained intact even after the durability test because no difference was observed between the XRD patterns before and after the test. The XRD patterns of the CsMnBr 3 and Cs 3 MnBr 5 nanocrystals before and after the durability test are presented in Fig. 5 (b). Both samples exhibited identical XRD patterns before and after the test, indicating that the CsMnBr 3 and Cs 3 MnBr 5 structures were not degraded during the durability test. Conclusions We discovered the crystal phase transition of lead-free cesium manganese bromine perovskite nanocrystal from hexagonal CsMnBr 3 to tetragonal Cs 3 MnBr 5 due to change the concentration of TOP solvent for the first time. The CsMnBr 3 nanocrystals had a hexagonal structure and exhibited a dispersed hexagonal morphology with an average size of ~ 20 nm and an interplanar spacing of 0.3 nm. The Cs 3 MnBr 5 nanocrystals had a tetragonal structure and exhibiting a dispersed tetragonal morphology with an average size of ~ 30 nm and an interplanar spacing of 0.33 nm. The compositional change between the CsMnBr 3 and Cs 3 MnBr 5 nanocrystals was determined by the amount of TOP solvent, the nanocrystal phase is changed from CsMnBr 3 to Cs 3 MnBr 5 as the amount of TOP increases. The emission peaks of the CsMnBr 3 and Cs 3 MnBr 5 nanocrystals were observed to be at 650 nm (FWHM = 95 nm) and 520 nm (FWHM = 50 nm), respectively. With an increase in the amount of TOP solvent, the relative emission of red (CsMnBr 3 ) and green (Cs 3 MnBr 5 ) shifted toward green emission. To examine the stability of the lead-free cesium manganese bromine perovskite nanocrystals, durability tests were performed. The CsMnBr 3 and Cs 3 MnBr 5 nanocrystal powders fabricated from the nanocrystal solutions were subjected to high-temperature and high-humidity testing at 85°C and 85% humidity for 24 h. After the durability test, no change was observed in the PL intensity of the lead-free perovskite CsMnBr 3 nanocrystal however, an increase in red emission was observed for the metal halide Cs 3 MnBr 5 nanocrystal. Our study demonstrates that phase-tunable synthesis between lead-free perovskite CsMnBr 3 and metal halide Cs 3 MnBr 5 nanocrystals can be easily achieved by controlling the amount of TOP solvent; it’s material represents a potential next-generation luminescence material for mini LED devices and applications in optoelectronic devices. Method Materials Cesium carbonate (Cs 2 CO 3 , purity; 99.995%), manganese(II) bromide (MnBr 2 , purity; 98%), 1-octadecene (ODE, technical grade; 90%), trioctylphosphine (TOP, technical grade; 90%), oleic acid (OA, technical grade; 90%), and oleylamine (OLA, technical grade; 90%) were purchased from Aldrich. Synthesis of CsMnBr 3 and Cs 3 MnBr 5 nanocrystal Cs-oleate was prepared by mixing 0.13 g Cs 2 CO 3 , 0.55 mL OA, 0.4 mL OLA, and 12 mL ODE in a 30 mL glass vial for 1 h at 170°C for dissolution. The solution containing MnBr 2 was prepared by mixing 0.5369 g MnBr 2 and 5–20 mL TOP in a 30 mL glass vial at 170°C for 1 h; then, Cs-oleate was quickly injected into the solution containing MnBr 2 . The CsMnBr 3 or Cs 3 MnBr 5 nanocrystal solutions reacted at 170°C for 1 min and were cooled in an ice-water bath to suppress the crystal growth of the nanocrystals. The obtained CsMnBr 3 /Cs 3 MnBr 5 nanocrystal solution was separated via centrifugation at 4000 rpm for 5 min. Characterizations The crystal structure of the CsMnBr 3 and Cs 3 MnBr 5 nanocrystal was identified using X-ray powder diffraction (XRD; Rigaku SmartLab) analysis, and the microstructure and morphology of the nanocrystals was characterized using transmission electron microscopy (TEM; JEOL). The photoluminescence (PL) spectrum was recorded at room temperature using a fluorescence spectrophotometer (PSI, DARSA PRO-3400), and the emission spectrum was obtained at an excitation wavelength of 365 nm. The lead-free cesium manganese bromine perovskite nanocrystal powder was prepared using the nanocrystal solution; a durability test was performed at 85°C and 85% humidity for 24 h. Declarations Acknowledgement This research was financially supported by the Ministry of Trade, Industry and Energy (MOTIE) and Korea Institute for Advancement of Technology (KIAT) through the International Cooperative R&D program (P0006844_Development of color conversion nanocrystal luminescence materials for next generation display). Author Contributions T. W. Kang, J. Hwang, B. S. Bae and S. W. Kim, contributed to the design experiments, interpreted the data and prepared the paper. E. J. Choi and Y. J. Park contributed to the experiments. All authors discussed the results and reviewed the manuscript. Additional Information The authors declare no competing financial interest. References MØLLER, C. K. Crystal structure and photoconductivity of caesium plumbohalides. Nature 182 , 1436 (1958). Poglitsch, A. & Weber, D. Dynamic disorder in methylammonium- trihalogenoplumbates (II) observed by millimeter-wave spectroscopy. J. Chem. Phy. 87 , 6373-6378 (1987). Weber, D. CH 3 NH 3 PbX 3 , ein Pb(II)-System mit kubischer Perowskitstruktur/CH 3 NH 3 PbX 3 , a Pb(II)-System with Cubic Perovskite Structure. Naturforsch. B 33 , 1443-1445 (1978). Onoda-Yamamuro, N., Matsuo, T. & Suga, H. Dielectric study of CH 3 NH 3 PbX 3 (X= Cl, Br, I). J. Phys. Chem. Solids 53 , 935-939 (1992). Papavassiliou, G. C. & Koutselas, I. B. Structural, optical and related properties of some natural three-and lower-dimensional semiconductor systems. Synth. Met. 71 , 1713-1714 (1995). Song, J., Li, J., Li, X., Xu, L., Dong, Y. & Zeng, H. Quantum Dot Light-Emitting Diodes Based on Inorganic Perovskite Cesium Lead Halides (CsPbX 3 ). Adv. Mater. 27 , 7162-7167 (2015). Pan, J., et al. Highly Efficient Perovskite-Quantum-Dot Light-Emitting Diodes by Surface Engineering. Adv. Mater. 28 , 8718-8725 (2016). Zhang, X., et al. Enhancing the Brightness of Cesium Lead Halide Perovskite Nanocrystal Based Green Light-Emitting Devices through the Interface Engineering with Perfluorinated Ionomer. Nano Lett. 16 , 1415-1420 (2016). Wang, Y., Li, X., Song, J., Xiao, L., Zeng, H. &Sun, H. All-Inorganic Colloidal Perovskite Quantum Dots: A New Class of Lasing Materials with Favorable Characteristics. Adv. Mater. 27 , 7101-7108 (2016). Li, X., et al. Healing All-Inorganic Perovskite Films via Recyclable Dissolution- Recyrstallization for Compact and Smooth Carrier Channels of Optoelectronic Devices with High Stability. Adv. Funct. Mater. 26 , 5903-5912 (2016). Ramasamy, P., Lim, D. H., Kim, B., Lee, S. H., Lee, M. S. & Lee, J. S. All-inorganic cesium lead halide perovskite nanocrystals for photodetector applications. Chem. Commun. 52 , 2067-2070 (2016). Protesescu, L., et al. Nanocrystals of Cesium Lead Halide Perovskites (CsPbX 3 , X = Cl, Br, and I): Novel Optoelectronic Materials Showing Bright Emission with Wide Color Gamut. Nano Lett. 15 , 3692-3696 (2015). Kulkarni, S. A., Mhaisalkar, S. G., Mathews, N. & Boix, P. P. Perovskite nanoparticles: synthesis, properties, and novel applications in photovoltaics and LEDs. Small Methods 3 , 1800231 (2019). Kamat, P. V., Bisquert, J. & Buriak, J. Lead-free perovskite solar cells. ACS Energy Letters 2 , 904-905 (2017). McDonald, C., et al. Nanostructured perovskite solar cells. Nanomaterials 9 , 1481 (2019). Takenaka, T. & Nagata, H. Current status and prospects of lead-free piezoelectric ceramics. J. Eur. Ceram. Soc. 25 , 2693-2700 (2005). Shi, Z., et al. Lead-free organic–inorganic hybrid perovskites for photovoltaic applications: recent advances and perspectives. Adv. Mater . 29 , 1605005 (2017). Hao, F., Stoumpos, C. C., Cao, D. H., Chang, R. P. H. & Kanatzidis, M. G. Lead-free solid-state organic-inorganic halide perovskite solar cells. Nat. Photonics 8 , 489−494 (2014). Ju, M. G., Dai, J., Ma, L. & Zeng, X. C. Lead-Free Mixed Tin and Germanium Perovskites for Photovoltaic Application. J. Am. Chem. Soc. 139 , 8038−8043 (2017). Almutlaq, J., et al. CsMnBr 3 : Lead-Free Nanocrystals with High Photoluminescence Quantum Yield and Picosecond Radiative Lifetime. ACS Materials Lett. 3 , 290-297 (2021). Su, B., Molokeev, M. S. & Xia, Z. Mn 2+ -Based narrow-band green-emitting Cs 3 MnBr 5 phosphor and the performance optimization by Zn 2+ alloying. J. Mater. Chem. C 7 , 11220-11226 (2019). Shao, L., et al. Broadband Ultraviolet Photodetectors Based on Cerium Doped Lead-Free Cs 3 MnBr 5 Metal Halide Nanocrystals. ACS Sustainable Chem. Eng. 9 , 4980-4987 (2021). Kwon, S. B., et al. Organic solvent-free lyophilization assisted recrystallization synthesis of high-purity green emissive Cs 3 MnX 5 (X = I, Br). J. Alloy Compd. 845, 156324 (2020). Lin, J., et al. Atomically Precise Doping of Monomanganese Ion into Coreless Supertetrahedral Chalcogenide Nanocluster Inducing Unusual Red Shift in Mn 2+ Emission. J. Am. Chem. Soc. 136 , 4769−4779 (2014). Orive, J., et al. Enhancement of the Luminescent Properties of a New Red-Emitting Phosphor, Mn 2 (HPO 3 )F 2 , by Zn Substitution. Inorg. Chem. 50 , 12463−12476 (2011). Palumbo, D. T. & Brown, J. J. Electronic States of Mn 2+ -Activated Phosphors.: I. Green-Emitting Phosphors. J. Electrochem. Soc. 117 , 1184-1188 (1970). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-805887","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":45385732,"identity":"66959a94-e398-4ebe-8be4-c106cc382026","order_by":0,"name":"Tae Wook Kang","email":"","orcid":"","institution":"Korea Institute of Ceramic Engineering and Technology","correspondingAuthor":false,"prefix":"","firstName":"Tae","middleName":"Wook","lastName":"Kang","suffix":""},{"id":45385733,"identity":"8492ee1e-a684-4a98-8f06-9c84c5565dbf","order_by":1,"name":"Eun Jin Choi","email":"","orcid":"","institution":"Korea Institute of Ceramic Engineering and 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07:29:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-805887/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-805887/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":12419141,"identity":"c3c3bc17-855c-4fa8-bfc3-d8c64245a950","added_by":"auto","created_at":"2021-08-13 18:44:54","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":82992,"visible":true,"origin":"","legend":"XRD patterns of the lead-free cesium manganese bromine perovskite nanocrystals by modified hot-injection method with the amount of TOP solvent.","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-805887/v1/12b6ed8f6dbb3969c7e4225e.jpg"},{"id":12419142,"identity":"5a3469b4-f6b2-43f1-98e5-407ca1228bfc","added_by":"auto","created_at":"2021-08-13 18:44:55","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":196926,"visible":true,"origin":"","legend":"Schematic of (a) CsMnBr3 crystal structure with (b) the ab plane illustrating the octahedral coordination of Mn2+, and (c) Cs3MnBr5 crystal structure with (d) the ab plane illustrating the tetrahedral coordination of Mn2+.","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-805887/v1/19273fc5a92c80fe52706f72.jpg"},{"id":12419217,"identity":"6936dc95-8b6f-43af-8601-4bee0c86679d","added_by":"auto","created_at":"2021-08-13 18:47:55","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":452602,"visible":true,"origin":"","legend":"Low- and high-resolution TEM images of the synthesized nanocrystals prepared using different amount of TOP solvent: (a) CsMnBr3 (10 mL), (b) Cs3MnBr5 (20 mL).","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-805887/v1/ea011703cd802632eea3f653.jpg"},{"id":12419144,"identity":"dd84869a-ca0f-4a01-8f33-83274dd9ae34","added_by":"auto","created_at":"2021-08-13 18:44:55","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":88128,"visible":true,"origin":"","legend":"PL spectra of CsMnBr3 and Cs3MnBr5 nanocrystals with the amount of TOP solvent. ","description":"","filename":"Fig4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-805887/v1/4584a75bacd90e707d2b3eb1.jpg"},{"id":12419145,"identity":"ea6d09b1-e21d-42b9-afcf-e43e0c9f0f0b","added_by":"auto","created_at":"2021-08-13 18:44:55","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":255251,"visible":true,"origin":"","legend":"(a) PL spectra of the high-temperature and high-humidity testing of lead-free perovskite CsMnBr3 (red) and metal halide Cs3MnBr5 (green) nanocrystals at 85 °C and 85% humidity for 24 h, and (b) XRD patterns of the CsMnBr3 and Cs3MnBr5 nanocrystals before and after the durability test.","description":"","filename":"Fig5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-805887/v1/b15d67632f8fa826b1f48e23.jpg"},{"id":13710021,"identity":"317ffa3a-427d-4252-9e65-d9af13bd72fb","added_by":"auto","created_at":"2021-09-17 14:15:56","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":755263,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-805887/v1/8b8b238c-766d-46f2-9410-8901f35979ef.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eDiscovery of the Crystal Phase Transition on Lead-free Cesium Manganese Bromine Perovskite Nanocrystal by Solvent Concentration\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eLead halide perovskites, which have the general formula APbX\u003csub\u003e3\u003c/sub\u003e (where A\u0026thinsp;=\u0026thinsp;CH\u003csub\u003e3\u003c/sub\u003eNH\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e (MA), HC(NH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e (FA), or Cs\u003csup\u003e+\u003c/sup\u003e; X\u0026thinsp;=\u0026thinsp;Cl, Br or I), has been studied since the middle of the 20th century [\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Among these perovskites, inorganic cesium lead halide perovskite (Cs\u003csub\u003en\u003c/sub\u003ePbX\u003csub\u003e2+n\u003c/sub\u003e, X\u0026thinsp;=\u0026thinsp;Cl, Br, I, or a mixture thereof) nanocrystals have attracted significant attention as an optical material for display and lamp applications (e.g. color converter material), as an alternative to quantum dot materials. Within the past decade, there have been rapid advances in the synthesis of cesium lead halide perovskite nanocrystals for use in solar cells, light-emitting diodes (LEDs), lasers, and photodetectors because of the excellent optoelectronic performance of these perovskite nanocrystals [\u003cspan additionalcitationids=\"CR7 CR8 CR9 CR10 CR11 CR12\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. They have interesting optical, excitonic, and charge-transport properties, including an outstanding photoluminescence quantum yield (PLQY) and tunable optical bandgap.\u003c/p\u003e \u003cp\u003eDespite these advantages, however, the presence of Pb, a toxic element, in perovskite nanocrystals raises critical concerns with regard to commercialization. This is because the heavy metal Pb can affect human health and the environment [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The US EPA has set the maximum allowable content of Pb in air and water as 0.15 \u0026micro;g/L and 15 \u0026micro;g/L, respectively. The European Union regulates the use of heavy and toxic materials (including Pb) in electronic devices, and the use of lead-based technology is expected to decline in the future [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] Therefore, the development of a lead-free cesium halide perovskite that retains the outstanding properties of cesium lead halide nanocrystals is important, and several studies have been conducted recently in this regard.\u003c/p\u003e \u003cp\u003eMetallic elements that have an electronic structure similar to that of Pb and can thus form stable perovskite structures\u0026mdash;such as Sn, Sb, Bi, Eu, and Yb\u0026mdash;have been considered as alternatives for Pb. Various lead-free halide perovskite nanocrystals, including those containing the aforementioned metal elements, have recently been developed and have achieved optoelectronic performance comparable to that of Pb-based counterparts [\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. These encouraging results obtained via exploration of lead-free perovskite nanocrystals indicate a major imminent breakthrough in the fabrication of new optoelectronic devices.\u003c/p\u003e \u003cp\u003eIn this study, to obtain lead-free inorganic halide perovskite nanocrystals, we focused on replacing Pb with the transition metal Mn. Mn has an ionic radius (0.083 nm for 6 coordination) similar to that of Pb (0.119 nm for 6 coordination), as well as a low toxicity, and has therefore attracted attention as a substitute for the B site in halide perovskites. Cesium manganese bromide perovskite nanocrystals, such as the red-emitting CsMnBr\u003csub\u003e3\u003c/sub\u003e and green-emitting Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e, have been reported to exhibit excellent optical properties [\u003cspan additionalcitationids=\"CR21 CR22\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In this paper, we synthesized red-emitting CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e perovskite nanocrystals using the modified hot-injection method and investigated the optical properties of these perovskite nanocrystals. Furthermore, we investigated the phase-tunable synthesis from Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e to CsMnBr\u003csub\u003e3\u003c/sub\u003e with controlling the amount of solvent.\u003c/p\u003e"},{"header":"Results And Discussion","content":"\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e shows the XRD patterns of the cesium manganese bromide perovskite nanocrystals with the amount of TOP solvent as well as the standard XRD patterns of the CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e from JCPDS card No. 26\u0026ndash;0387 and No. 27\u0026ndash;0117, respectively. The crystal structures of CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e are shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e. The crystal structure of CsMnBr\u003csub\u003e3\u003c/sub\u003e consists of linear chains of distorted face-sharing [MnBr\u003csub\u003e6\u003c/sub\u003e] octahedron with a D\u003csub\u003e3d\u003c/sub\u003e symmetry parallel to the c-axis, that are bridged by Cs ions. Interestingly, the Mn\u0026thinsp;\u0026minus;\u0026thinsp;Mn distance is very short (~\u0026thinsp;0.32982 nm) along the c-axis, leading to strongly coupled optical transitions. The XRD pattern of the sample prepared with 10 mL TOP solvent was indexed to the standard hexagonal CsMnBr\u003csub\u003e3\u003c/sub\u003e structure (JCPDS No. 26\u0026ndash;0387); this sample contains the P6\u003csub\u003e3\u003c/sub\u003e/mmc (#194) space group and has lattice parameters a\u0026thinsp;=\u0026thinsp;b\u0026thinsp;=\u0026thinsp;0.785878 nm and c\u0026thinsp;=\u0026thinsp;0.659641 nm. In the crystal structure of Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e, the Mn\u003csup\u003e2+\u003c/sup\u003e ions are coordinated by four Br\u003csup\u003e-\u003c/sup\u003e ions to form a [MnBr\u003csub\u003e4\u003c/sub\u003e] regular tetrahedron geometry with D\u003csub\u003e2d\u003c/sub\u003e symmetry. The Mn\u003csup\u003e2+\u003c/sup\u003e site layers are separated by Cs\u003csup\u003e+\u003c/sup\u003e site layers in the direction of the c-axis, and the adjacent [MnBr\u003csub\u003e4\u003c/sub\u003e] tetrahedrons maintain a distance of 0.780593(6) nm. The XRD pattern of the sample prepared with 20 mL TOP solvent corresponds to a single-phase tetragonal Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e structure (JCPDS No. 27\u0026ndash;0117); this sample has the I4/mcm (#140) space group and lattice constants a\u0026thinsp;=\u0026thinsp;b\u0026thinsp;=\u0026thinsp;0.992839 nm and c\u0026thinsp;=\u0026thinsp;1.561187 nm. The nanocrystal samples prepared with 12.5 and 17.5 mL TOP solvent exhibit a mixed phase with hexagonal CsMnBr\u003csub\u003e3\u003c/sub\u003e and tetragonal Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e phases, and the phase transition of nanocrystal phase from CsMnBr\u003csub\u003e3\u003c/sub\u003e to Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e was observed as the amount of TOP solvent increased.\u003c/p\u003e\n\u003cp\u003eThe morphology of the synthesized nanocrystals with the amount of TOP solvent was analyzed using high-resolution TEM, as shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e. The TEM images of lead-free perovskite CsMnBr\u003csub\u003e3\u003c/sub\u003e nanocrystals present a dispersed hexagonal morphology with an average size of ~\u0026thinsp;20 nm. The interplanar spacing relative to the (021) crystalline planes of the CsMnBr\u003csub\u003e3\u003c/sub\u003e nanocrystals is about 0.3 nm. In contrast, the TEM image of Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals shows a dispersed tetragonal morphology with an average size of ~\u0026thinsp;30 nm. The interplanar spacing relative to the (213) crystalline planes of the Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals is about 0.33 nm. The nanocrystals prepared with 12.5 and 17.5 mL TOP solvent coexist with the CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals; the compositional change between the CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals is determined by the amount of TOP solvent.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e presents the PL spectra of the obtained nanocrystals with the amount of TOP solvent. The inset images show the emission of the nanocrystals under irradiation with a 365 nm UV lamp; their color changes from red to green as the amount of TOP solvent increases from 10 to 20 mL. The emission spectrum of the lead-free perovskite CsMnBr\u003csub\u003e3\u003c/sub\u003e nanocrystals exhibits a broad red emission peak centered at 650 nm with a full-width-at-half-maximum (FWHM) of 95 nm. The red PL emission which assigned \u003csup\u003e4\u003c/sup\u003eT\u003csub\u003e1\u003c/sub\u003e\u0026rarr;\u003csup\u003e6\u003c/sup\u003eA\u003csub\u003e1\u003c/sub\u003e transition in [MnBr\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e4-\u003c/sup\u003e octahedrons of the CsMnBr\u003csub\u003e3\u003c/sub\u003e nanocrystals is considered to be due to the relaxation from the lowest excited state to the ground state of Mn\u003csup\u003e2+\u003c/sup\u003e ions. This is consistent with reports of red emission from Mn\u003csup\u003e2+\u003c/sup\u003e in the MnBr\u003csub\u003e6\u003c/sub\u003e octahedron [\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e]. On the other hand, the emission spectrum of the Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals shows green emission at 520 nm with an FWHM of 50 nm. The strong green emission is ascribed to the metal-centered d\u0026ndash;d transition of the Mn\u003csup\u003e2+\u003c/sup\u003e ion in the d\u003csup\u003e5\u003c/sup\u003e configuration with a [MnBr\u003csub\u003e4\u003c/sub\u003e] tetrahedral coordination geometry [\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e]. Interestingly, the PL spectra of the Cs\u0026ndash;Mn\u0026ndash;Br nanocrystals can be controlled by simply changing the amount of TOP solvent, as depicted in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. With an increase of the amount of TOP solvent, the relative emission of red (CsMnBr\u003csub\u003e3\u003c/sub\u003e) and green (Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e) shifts toward green emission, implying that our study can achieve tunable the color between green and red by simply controlling the amount of TOP solvent.\u003c/p\u003e\n\u003cp\u003eTo evaluate the thermal and chemical stability of the CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals, a durability test was performed under high-temperature and high-humidity conditions of 85\u0026deg;C and 85%, respectively, for 24 h. The PL behaviors of the CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals after the durability test are shown in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e (a). The lead-free perovskite CsMnBr\u003csub\u003e3\u003c/sub\u003e nanocrystal powder exhibits extremely high durability and maintains its initial PL intensity. In comparison, the PL intensity of the metal halide Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystal powder does not decrease but rather increases in the red emission (CsMnBr\u003csub\u003e3\u003c/sub\u003e) region. It is considered that the materials that remained unreacted during the preparation of the nanocrystals reacted to form more CsMnBr\u003csub\u003e3\u003c/sub\u003e nanocrystals due to the high temperature during the durability test. Both nanocrystals exhibited no change in the PL peak wavelength and FWHM values after the durability test. The structures of CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e are considered to have remained intact even after the durability test because no difference was observed between the XRD patterns before and after the test. The XRD patterns of the CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals before and after the durability test are presented in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e (b). Both samples exhibited identical XRD patterns before and after the test, indicating that the CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e structures were not degraded during the durability test.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eWe discovered the crystal phase transition of lead-free cesium manganese bromine perovskite nanocrystal from hexagonal CsMnBr\u003csub\u003e3\u003c/sub\u003e to tetragonal Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e due to change the concentration of TOP solvent for the first time. The CsMnBr\u003csub\u003e3\u003c/sub\u003e nanocrystals had a hexagonal structure and exhibited a dispersed hexagonal morphology with an average size of ~\u0026thinsp;20 nm and an interplanar spacing of 0.3 nm. The Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals had a tetragonal structure and exhibiting a dispersed tetragonal morphology with an average size of ~\u0026thinsp;30 nm and an interplanar spacing of 0.33 nm. The compositional change between the CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals was determined by the amount of TOP solvent, the nanocrystal phase is changed from CsMnBr\u003csub\u003e3\u003c/sub\u003e to Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e as the amount of TOP increases. The emission peaks of the CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals were observed to be at 650 nm (FWHM\u0026thinsp;=\u0026thinsp;95 nm) and 520 nm (FWHM\u0026thinsp;=\u0026thinsp;50 nm), respectively. With an increase in the amount of TOP solvent, the relative emission of red (CsMnBr\u003csub\u003e3\u003c/sub\u003e) and green (Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e) shifted toward green emission. To examine the stability of the lead-free cesium manganese bromine perovskite nanocrystals, durability tests were performed. The CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystal powders fabricated from the nanocrystal solutions were subjected to high-temperature and high-humidity testing at 85\u0026deg;C and 85% humidity for 24 h. After the durability test, no change was observed in the PL intensity of the lead-free perovskite CsMnBr\u003csub\u003e3\u003c/sub\u003e nanocrystal however, an increase in red emission was observed for the metal halide Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystal. Our study demonstrates that phase-tunable synthesis between lead-free perovskite CsMnBr\u003csub\u003e3\u003c/sub\u003e and metal halide Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals can be easily achieved by controlling the amount of TOP solvent; it\u0026rsquo;s material represents a potential next-generation luminescence material for mini LED devices and applications in optoelectronic devices.\u003c/p\u003e"},{"header":"Method","content":"\u003cp\u003e \u003cem\u003eMaterials\u003c/em\u003e Cesium carbonate (Cs\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e, purity; 99.995%), manganese(II) bromide (MnBr\u003csub\u003e2\u003c/sub\u003e, purity; 98%), 1-octadecene (ODE, technical grade; 90%), trioctylphosphine (TOP, technical grade; 90%), oleic acid (OA, technical grade; 90%), and oleylamine (OLA, technical grade; 90%) were purchased from Aldrich.\u003c/p\u003e \u003cp\u003e \u003cem\u003eSynthesis of CsMnBr\u003c/em\u003e \u003csub\u003e \u003cem\u003e3\u003c/em\u003e \u003c/sub\u003e \u003cem\u003eand Cs\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eMnBr\u003c/em\u003e\u003csub\u003e\u003cem\u003e5\u003c/em\u003e\u003c/sub\u003e \u003cem\u003enanocrystal\u003c/em\u003e Cs-oleate was prepared by mixing 0.13 g Cs\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e, 0.55 mL OA, 0.4 mL OLA, and 12 mL ODE in a 30 mL glass vial for 1 h at 170\u0026deg;C for dissolution. The solution containing MnBr\u003csub\u003e2\u003c/sub\u003e was prepared by mixing 0.5369 g MnBr\u003csub\u003e2\u003c/sub\u003e and 5\u0026ndash;20 mL TOP in a 30 mL glass vial at 170\u0026deg;C for 1 h; then, Cs-oleate was quickly injected into the solution containing MnBr\u003csub\u003e2\u003c/sub\u003e. The CsMnBr\u003csub\u003e3\u003c/sub\u003e or Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystal solutions reacted at 170\u0026deg;C for 1 min and were cooled in an ice-water bath to suppress the crystal growth of the nanocrystals. The obtained CsMnBr\u003csub\u003e3\u003c/sub\u003e/Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystal solution was separated via centrifugation at 4000 rpm for 5 min.\u003c/p\u003e \u003cp\u003e \u003cem\u003eCharacterizations\u003c/em\u003e The crystal structure of the CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystal was identified using X-ray powder diffraction (XRD; Rigaku SmartLab) analysis, and the microstructure and morphology of the nanocrystals was characterized using transmission electron microscopy (TEM; JEOL). The photoluminescence (PL) spectrum was recorded at room temperature using a fluorescence spectrophotometer (PSI, DARSA PRO-3400), and the emission spectrum was obtained at an excitation wavelength of 365 nm. The lead-free cesium manganese bromine perovskite nanocrystal powder was prepared using the nanocrystal solution; a durability test was performed at 85\u0026deg;C and 85% humidity for 24 h.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was financially supported by the Ministry of Trade, Industry and Energy (MOTIE) and Korea Institute for Advancement of Technology (KIAT) through the International Cooperative R\u0026amp;D program (P0006844_Development of color conversion nanocrystal luminescence materials for next generation display).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eT. W. Kang, J. Hwang, B. S. Bae and S. W. Kim, contributed to the design experiments, interpreted the data and prepared the paper. E. J. Choi and Y. J. Park contributed to the experiments. All authors discussed the results and reviewed the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional Information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing financial interest.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eM\u0026Oslash;LLER, C. K. Crystal structure and photoconductivity of caesium plumbohalides. \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e182\u003c/strong\u003e, 1436 (1958).\u003c/li\u003e\n \u003cli\u003ePoglitsch, A. \u0026amp; Weber, D. Dynamic disorder in methylammonium- trihalogenoplumbates (II) observed by millimeter-wave spectroscopy. \u003cem\u003eJ. Chem. Phy.\u003c/em\u003e \u003cstrong\u003e87\u003c/strong\u003e, 6373-6378 (1987).\u003c/li\u003e\n \u003cli\u003eWeber, D. 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Soc.\u003c/em\u003e \u003cstrong\u003e117\u003c/strong\u003e, 1184-1188 (1970).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"CsMnBr3 perovskite nanocrystals, Metal halide Cs3MnBr5 nanocrystal, Phase-tunable synthesis","lastPublishedDoi":"10.21203/rs.3.rs-805887/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-805887/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWe have been demonstrated the crystal phase transition for lead-free cesium manganese bromine perovskite nanocrystal synthesized by the modified hot-injection method due to change the concentration of solvent (trioctylphosphine; TOP). The compositions to be synthesized were determined by the amount of TOP solvent, and the structure phase of nanocrystal was changed from hexagonal CsMnBr\u003csub\u003e3\u003c/sub\u003e to tetragonal Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e as the amount of TOP solvent increased. The emission peaks of CsMnBr\u003csub\u003e3\u003c/sub\u003e and Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystals were observed at 650 nm (red) and 520 nm (green), respectively. After a durability test at 85 °C and 85% humidity for 24 h, the lead-free perovskite CsMnBr\u003csub\u003e3\u003c/sub\u003e nanocrystal powder maintained its initial emission intensity, and the metal halide Cs\u003csub\u003e3\u003c/sub\u003eMnBr\u003csub\u003e5\u003c/sub\u003e nanocrystal powder exhibited an increase in red emission due to the post-synthesis of CsMnBr\u003csub\u003e3\u003c/sub\u003e nanocrystals.\u003c/p\u003e","manuscriptTitle":"Discovery of the Crystal Phase Transition on Lead-free Cesium Manganese Bromine Perovskite Nanocrystal by Solvent Concentration","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2021-08-13 18:44:53","doi":"10.21203/rs.3.rs-805887/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3b7caa10-c5eb-43e5-ab15-4588b58eb34d","owner":[],"postedDate":"August 13th, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":6447908,"name":"Optical Materials and Devices"}],"tags":[],"updatedAt":"2021-08-27T10:29:04+00:00","versionOfRecord":[],"versionCreatedAt":"2021-08-13 18:44:53","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-805887","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-805887","identity":"rs-805887","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}