Open Access
Add to BibSonomy
Abstract
All inorganic perovskite CsPbBr3 shows great potential in laser device because of its excellent luminescence characteristics, while the room temperature amplified spontaneous emission (ASE) in a large size CsPbBr3 bulk single crystal is still quite difficult. Herein, we have obtained the room temperature ASE in a sub-centimeter size CsPbBr3 bulk single crystal pumped with the single-photon excitation. Based on the reproducible light path within the CsPbBr3 bulk single crystal, the photonic feedback between the bottom and top facets naturally enhances the population inversion, which exhibits an amplified spontaneous emission threshold of ∼320 µJ/cm2. The blue shift of the ASE peak along with the increased pumping intensity is also observed and ascribed to the reduction of the refractive index and the energy band filling effect. These findings demonstrate the sub-centimeter size CsPbBr3 bulk single crystal to be an excellent candidate as an optical gain media for crystal lasers.
© 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
As a star material with outstanding optoelectronic characteristics including long carrier diffusion length, large optical absorption coefficient, large optical gain, and adjustable bandgaps, lead halide perovskite has been widely applied for optoelectronic devices such as light emitting diodes, lasers, solar cells, and photodetectors [1–4]. Organic-inorganic hybrid perovskites MAPbX3 (where MA = methyl ammonium and X = Cl, Br or I, or mixed Cl/Br and Br/I systems) is first reported and shows excellent performance in solar cells [5]. However, the surface degradation of the hybrid perovskite usually occurs in the ambient environment, in which the oxygen and moisture will lead to the decomposition of the perovskite. Compared to the traditional hybrid perovskite structure, all inorganic perovskite CsPbBr3 by substituting organic cation with cesium (Cs+) exhibits a much better atmospheric stability, a narrower line width, and a higher photoluminescence (PL) quantum yield [6–10]. Especially, recent reports reveal that CsPbBr3 nanocrystals and quantum dots are employed as the active layer for high stable and efficiency white light emitting diode, which also suggests its potential application in high-CRI warm white light luminescence and visible light communication [11–14].
Among optoelectronic devices, laser is one kind of coherent light source which can be widely employed in optical communication, biological labeling, and high-density data storage. To date, CsPbBr3 based lasers working at random lasing mode [15–17], whispering gallery mode (WGM) [18–20], and Fabry-Pérot (F-P) mode [21–24] have been reported. However, most of the current reported CsPbBr3 lasers mainly focus on the micro/nano structures including microcube, nanoplate, microdisk, quantum dot, and nanocrystals. Owing to the quantum confinement effect, the lasing threshold of the micro/nano structures can be reduced significantly. Furthermore, as the prerequisite for lasing, ASE in CsPbBr3 is also typically observed from micro/nano structures like nanoparticle [25], nanocrystal [26,27], quantum dot [28–30], nano film [31], and microplate [32]. While compared to the micro/nano structures, the large size bulk single crystal reveals more difficulty in ASE but more promising in practical applications. Typically, one-photon induced ASE in bulk crystal is rather difficult because of the limited photon penetration depth and reabsorption of the material. Kim et al. report a room temperature ASE in CsPbBr3 bulk crystal with different excited wavelengths [33]. Under the excitation of 520 nm pulse laser, a high ASE threshold of 46 MW/cm2 (1.38 mJ/cm2) and a narrow full width at half maximum (FWHM) of 4 nm are measured. In addition, the ASE active point usually occurs near the crystal edge, indicating the existence of microcrystal with loose or cracked surfaces. Compared with one-photon excitation, two-photon excitation is a nonlinear process with long penetration depth and less Rayleigh scattering. Zhao et al. [34] realize a much lower threshold ASE (0.65 mJ/cm2) in millimeter size CsPbBr3 crystal by employing 800 nm pulse laser as excited source, while the FWHM (7 nm) is much larger than that reported by Kim [33]. To date, studies regrading ASE in CsPbBr3 bulk single crystal laser are still rare, and different kinds of bulk structure are also favorable in order to further reduce the ASE threshold.
In this work, we have first successfully achieved a sub-centimeter size CsPbBr3 bulk single crystal. The sub-centimeter size single crystal is prepared through a simple and low-cost solution method. The as-prepared perovskite presents ideal stoichiometric ratio of 1:1:3 (Cs:Pb:Br) and no precipitate of Pb metal is detected. Then, the CsPbBr3 bulk single crystal is pumped by a pulse laser with wavelength of 355 nnm and repetition rate of 1000 Hz. Owing to the emission photons reflected by the two smooth facets of the CsPbBr3 bulk single crystal, one-photon excited room temperature ASE is realized with a threshold of ∼320 µJ/cm2. In addition, blue shifts of the ASE peak are observed as the excited intensity increases.
2. Experimental
2.1 Synthesis of materials
The preparation processes of the sub-centimeter size CsPbBr3 bulk single crystals were schematically presented in Fig. 1. Firstly, 15 mL dimethyl sulfoxide (DMSO) solution was added into a glass container, and then the PbBr2 (Aladdin, 99.99%) and CsBr (Aladdin, 99.99%) precursors (weight ratio of 1:1) were subsequently added into the DMSO solution. After that, the mixed PbBr2 and CsBr precursors were stirred for 30 min until the raw materials were completely dissolved. Then the saturated solution was loaded into an oven with temperature steadied at 60 °C. After 12 hours, the precipitated CsPbBr3 crystals can be collected when the DMSO solvent completely volatilized. Finally, the sub-centimeter size CsPbBr3 bulk single crystals were further blow dried and cleaned by ethanol and nitrogen gun.
2.2 Characterization
Optical microscope under both dark field and bright field conditions was employed to observe the morphology of the sub-centimeter size CsPbBr3 bulk single crystal. X-ray diffraction (XRD) with Cu Kα-line (0.154 nm) is utilized to study the crystal structure of the single crystal. The optical characteristics of the single crystal are investigated by room temperature Raman, photoluminescence (PL), and absorption spectra. X-ray photoelectron spectroscopy (XPS) is used to study the chemical state of Cs-3d, Pb-4f, and Br-3d core electrons.
2.3 ASE measurement
355 nm laser (100 fs, 1 kHz) with different pumping intensities is used as the excitation source to excite the sub-centimeter size CsPbBr3 bulk single crystal. Pumping spectra collected from the top facet (region II) and lateral facets (region I & II) were both studied for clarifying the pumping behavior of the single crystal. The pumping spectra were collected through a spectrometer with resolution of 0.09 nm (Princeton Instrument, SpectraPro HRS-300).
3. Results and discussion
Figure 2(a) presents the top view bright field optical image of a CsPbBr3 bulk single crystal under a 5x optical objective. The CsPbBr3 bulk single crystal shows a three-dimensional trapezoidal shape column structure with column length of ∼0.5 cm. Owing to the geometric shapes of the bulk single crystal doesn’t show an extremely regular boarder. Thus, the bottom margin length (L1/L5), top margin length (L2), and length (L3/L4) of the side profile are statistically measured and corresponding average values (L1/L5 = 1421 nm/1481 nm, L2 = 293 nm, L3/L4 = 632.5 nm/495 nm) are presented in Fig. S1. From the dark field optical image as shown in Fig. 2(b), the CsPbBr3 bulk single crystal reveals transparent characteristics to the yellow-orange lights. That is because of the lights from the white light source with wavelength longer than ∼550 nm can penetrate through the CsPbBr3 bulk single crystal. Figure 2(c-d) show the morphological difference between leg facets (facet I & III) and top facet (region II) of the CsPbBr3 crystal by the top view bright field optical images under the 10x and 20x optical objectives, respectively. Except some scratches formed by tweezer during the transfer process, the top facet (region II) exhibits a relative smooth surface, which is favorable for the formation of reflection cavity, which is apparently different from the side facets (region I & III). The zigzag surface of side facets will result in diffuse reflection when the pumping light irradiates. The different morphologies of crystal facets formed by the varied nucleation speeds, which will be systematically studied in future.
Fig. 2. The (a) bright field and (b) dark field optical images of the as-prepared CsPbBr3 bulk single crystal under a 5x optical objective; (c-d) The bright field optical images of the as-prepared CsPbBr3 bulk single crystal under the 10x and 20x optical objectives, respectively.
The sub-centimeter size CsPbBr3 bulk single crystal is placed onto a glass holder to study the crystal structure and corresponding XRD pattern is presented in Fig. 3(a). Besides the signal from the underneath holder, four distinct and sharp peaks located at 15.08°, 15.21°, 30.45°, and 30.70° are collected. These peaks can be respectively ascribed to the diffraction signals from the (002), (110), (004), and (220) facets of the orthorhombic CsPbBr3 with lattice constants of a = 8.2248 Å, b = 8.2741 Å, and c = 11.7748 Å [35]. Compared with previous report [11], an additional broad background XRD signal is probed in our sample and can be ascribed to the diffraction from a plasticine, which is commonly used for supporting the sample during the measurement. The room temperature Raman spectrum of the sub-centimeter size CsPbBr3 bulk single crystal is investigated under a back-scattering configuration by using a 785 nm laser as excitation source. Five peaks can be observed and assigned to the bending mode of Br-Pb-Br (40.6 cm−1 and 65.8 cm−1), antisymmetric stretching mode of Pb-Br (121.8 cm−1), symmetric stretching mode of Pb-Br (142.8 cm−1), and the second-order phonon mode of the [PbBr6]4- octahedron (310.0 cm−1) [36]. The UV-Vis absorption spectrum of the sub-centimeter size CsPbBr3 bulk single crystal is revealed in Fig. 3(c). Clearly, a sharp absorption edge locates at ∼540 nm is determined and corresponding bandgap is calculated as ∼2.3 eV. The PL spectrum indicated in Fig. 3(c) shows a broaden emission peak, which can be deconvoluted to two peaks centered at 528 nm and 539 nm. The time resolved PL decay trace of the sub-centimeter size CsPbBr3 bulk single crystal excited by a 360 nm pico-second laser is provided in Fig. 3(d). The PL life time decreases from 7.2 ns to 4.6 ns as the temperature increases from 100 K to 300 K. This is owing to the thermal expansion and lattice vibration of CsPbBr3 become server at higher temperature, which promotes the scattering between the phonons and photo-generated carriers and also reduces the recombination life time of the CsPbBr3.
Fig. 3. (a) The XRD pattern, (b) Raman spectrum, (c) absorption and PL spectra, (d) and temperature dependent time resolved PL spectra of the sub-centimeter size CsPbBr3 bulk single crystal.
The chemical states of the sub-centimeter size CsPbBr3 bulk single crystal are studied by XPS with a standard C-1s peak (284.5 eV) for calibration. In Fig. 4(a-c), all the XPS spectra of Cs-3d, Pb-4f, and Br-3d core electrons can be well deconvoluted to two symmetric Gaussian peaks, which can be ascribed to the spin-orbital splitting. The XPS peaks of the Cs-3d5/2, Cs-3d3/2, Pb-4f7/2, Pb-4f5/2, Br-3d5/2, and Br-3d3/2 orbitals are determined as 723.8 eV, 737.8 eV, 137.6 eV, 142.4 eV, 67.5 eV, and 68.5 eV, thus corresponding spin-orbital splitting of the Cs-3d, Pb-4f, and Br-3d core electrons are calculated as 14 eV, 4.8 eV, and 1 eV. In addition, no signal of the Pb metal can be detected, which is normally observed in other CsPbBr3 materials prepared by a solution method [37]. The valence band scanning spectrum of the CsPbBr3 is presented in Fig. 4(d). According to the intersection of linear fits to the valence band leading edge and the background, the position of the valence band maximum (VBM) with respect to the Fermi energy level can be calculated as ∼1.88 eV.
Fig. 4. The X-ray photoelectron spectroscopy (XPS) spectra of the (a) Cs-3d; (b) Pb-4f; and (c) Br-3d core electrons; (d) The valence band scanning spectrum of the CsPbBr3 bulk single crystal.
As schematic shown in Fig. 5(a), the pumping spectra collected from the top facet (region II) and lateral facets (region I & II) are studied by using a 355 nm laser (100 fs, 1 kHz) as excited source. As showed in Fig. 5(b), under the same pumping intensity (375 µJ/cm2), only the spectrum from the top facet reveals amplified spontaneous emission (ASE) with an additional sharp peak centered at ∼543.5 nm. According to the optical image of the CsPbBr3 bulk single crystal, the smooth surface of the top facet can be naturally identified as the reflection mirrors. However, diffuse reflections from the rough side facets (region I & III) rarely contribute to the amplified spontaneous emission. The PL spectra from region II under different pumping intensities are presented in Fig. 5(c). The PL intensity of the broad emission (composed by two peaks at 528 nm (A) and 539 nm (B)) gradually increases with the raised pumping intensity from 66 to 475 µJ/cm2. The A and B peaks are observed in both top facet (region II) and lateral facets (region I & II), which can be ascribed to the radiative recombination of excitons and P-band emission, respectively [33]. In addition, though their intensities monotonously increase with the increase of the pumping intensity (as shown in Figure S2), the peak positions maintain without any shifts (Fig. 5(f)). However, as the pumping intensity is at a high level, a sharp ASE peak emerges at ∼543.8 nm with dramatically increased intensities. Since the light path within the CsPbBr3 bulk single crystal is reproducible, the feedback of the emission photons between the bottom facet and the top facet subsequently leads to the ASE. As indicated in Fig. 5(d), the sharp emission peak blue shifts from ∼543.8 nm to ∼543.4 nm as the pumping intensity increases to 475 µJ/cm2. This result can be attributed to the reduction of the refractive index induced by the powerful generated carrier intensity and the energy band filling effect [38]. The threshold of the amplified spontaneous emission is studied by deriving the inflection point of the pumping intensity, which can be determined as ∼320 µJ/cm2 (as shown in Fig. 5(e)). Some ASE parameters of CsPbBr3 perovskites with different structures are summarized in Table 1. Apparently, compared with the bulk single crystal, CsPbBr3 micro/nano structures can easily realize one-photon and two-photon excited ASE with much lower energy threshold. In addition, our study presents a one-photon excited ASE with a low energy threshold.
Fig. 5. (a) Schematic diagram of the sub-centimeter size CsPbBr3 bulk single crystal pumped by a 355 nm laser (100 fs, 1 kHz); (b) The PL spectra from the different regions, inset is the far-field PL optical image; (c-d) The PL spectra collected from region II using different pumping intensities; (e) The PL intensity as a function of the pumping intensity; (f) The PL peak position as a function of the pumping intensity.
Table 1. Comparison of the ASE parameters reported for CsPbBr3 perovskites.
4. Conclusions
In summary, amplified spontaneous emission is reported on the sub-centimeter size CsPbBr3 bulk single crystal. The nucleation and crystallization of the CsPbBr3 bulk single crystal is realized through a simple and low-cost solution method. No precipitation of the Pb metal is observed owing to ideal stoichiometric ratio of the perovskite. Thanks to the naturally formation of the F-P cavity between the top and bottom facets of the bulk single crystal, a one-photon excited amplified spontaneous emission is realized with a threshold of ∼320 µJ/cm2. In addition, the blue shift of the ASE peak is also verified and ascribed to the energy band filling effect and the reduction of the refractive index. This study demonstrates the potential of the emerging all inorganic perovskite CsPbBr3 bulk single crystal as a working media for high-power crystal laser.
Funding
National Natural Science Foundation of China (52172149, 61705043); Dongguan University of Technology Startup Fund.
Acknowledgments
The authors thank Dr. F. Yi for her helpful discussion and improvement on this manuscript. The authors also acknowledge the Materials and Devices Testing Center at Tsinghua Shenzhen International Graduate School, Shenzhen 518055, China, and Dongguan University of Technology Analytical and Testing Center.
Disclosures
The authors declare that there are no conflicts of interest related to this article.
Data availability
The data that supports the findings of this study are available from the corresponding author upon reasonable request.
Supplemental document
See Supplement 1 for supporting content.
References
1. Z. Q. Li, E. Hong, X. Zhang, et al., “Perovskite-type 2D materials for high-performance photodetectors,” J. Phys. Chem. Lett. 13(5), 1215–1225 (2022). [CrossRef]
2. B. R. Sutherland and E. H. Sargent, “Perovskite photonic sources,” Nat. Photonics 10(5), 295–302 (2016). [CrossRef]
3. Z. Q. Li, X. Liu, C. Zuo, et al., “Supersaturation-controlled growth of monolithically integrated lead-free halide perovskite single-crystalline thin film for high-sensitivity photodetectors,” Adv. Mater. 33(41), 2103010 (2021). [CrossRef]
4. L. X. Su, T. F. Li, and Y. Zhu, “A vertical CsPbBr3/ZnO heterojunction for photo-sensing lights from UV to green band,” Opt. Express 30(13), 23330–23340 (2022). [CrossRef]
5. M. A. Green, A. H. Baillie, and H. J. Snaith, “The emergence of perovskite solar cells,” Nat. Photonics 8(7), 506–514 (2014). [CrossRef]
6. C. Dang, J. Lee, K. Roh, et al., “Highly efficient, spatially coherent distributed feedback lasers from dense colloidal quantum dot films,” Appl. Phys. Lett. 103(17), 171104 (2013). [CrossRef]
7. S. Alshaibani, O. Alkhazragi, I. Ashry, et al., “Wide-field-of-view optical detectors for deep ultraviolet light communication using all-inorganic CsPbBr3 perovskite nanocrystals,” Opt. Express 31(16), 25385–25397 (2023). [CrossRef]
8. X. Y. Shan, S. J. Zhu, R. J. Lin, et al., “Improvements of the modulation bandwidth and data rate of green-emitting CsPbBr3 perovskite quantum dots for Gbps visible light communication,” Opt. Express 31(2), 2195–2207 (2023). [CrossRef]
9. Z. F. Shi, Y. Li, Y. T. Zhang, et al., “High-efficiency and air-stable perovskite quantum dots light-emitting diodes with an all-inorganic heterostructure,” Nano Lett. 17(1), 313–321 (2017). [CrossRef]
10. Z. F. Shi, Y. Li, S. Li, et al., “Localized surface plasmon enhanced all-inorganic perovskite quantum dot light-emitting diodes based on coaxial core/shell heterojunction architecture,” Adv. Funct. Mater. 28(20), 1707031 (2018). [CrossRef]
11. B. Q. Wang, J. L. Peng, X. Yang, et al., “Template assembled large-size CsPbBr3 nanocomposite films toward flexible, stable, and high-performance X-Ray scintillators,” Laser Photonics Rev. 16(7), 2100736 (2022). [CrossRef]
12. D. D. Yan, S. Y. Zhao, Y. B. Zhang, et al., “Highly efficient emission and high-CRI warm white light-emitting diodes from ligand-modified CsPbBr3 quantum dots,” Opto-Electron. Adv. 5(1), 200075 (2022). [CrossRef]
13. Q. H. Mo, C. Chen, W. S. Cai, et al., “High-performance CsPbBr3@Cs4PbBr6/SiO2 nanocrystals via double coating layers for white light emission and visible light communication,” eScience 2(6), 646–654 (2022). [CrossRef]
14. H. L. Guan, S. Y. Zhao, H. X. Wang, et al., “Room temperature synthesis of stable single silica-coated CsPbBr3 quantum dots combining tunable red emission of Ag-In-Zn-S for High-CRI white light-emitting diodes,” Nano Energy 67, 104279 (2020). [CrossRef]
15. X. S. Tang, Y. Bian, Z. Z. Liu, et al., “Room-temperature up-conversion random lasing from CsPbBr3 quantum dots with TiO2 nanotubes,” Opt. Lett. 44(19), 4706–4709 (2019). [CrossRef]
16. C. L. Li, Z. G. Zang, C. Han, et al., “Highly compact CsPbBr3 perovskite thin films decorated by ZnO nanoparticles for enhanced random lasing,” Nano Energy 40, 195–202 (2017). [CrossRef]
17. S. Yuan, D. Q. Chen, X. Y. Li, et al., “In situ crystallization synthesis of CsPbBr3 perovskite quantum dot-embedded glasses with improved stability for solid-state lighting and random upconverted lasing,” ACS Appl. Mater. Interfaces 10(22), 18918–18926 (2018). [CrossRef]
18. S. Yakunin, L. Protesescu, F. Krieg, et al., “Low-threshold amplified spontaneous emission and lasing from colloidal nanocrystals of caesium lead halide perovskites,” Nat. Commun. 6(1), 8056 (2015). [CrossRef]
19. J. M. Li, J. M. Liu, E. R. Mei, et al., “Low threshold amplified spontaneous emission in ultrastable CsPbBr3-TS-1 nanocomposite films under two-photon excitation,” Appl. Phys. Lett. 119(9), 091102 (2021). [CrossRef]
20. B. E. Zhou, M. M. Jiang, H. X. Dong, et al., “High-temperature upconverted single-mode lasing in 3D fully inorganic perovskite microcubic cavity,” ACS Photonics 6(3), 793–801 (2019). [CrossRef]
21. Y. G. Zhong, K. Liao, W. N. Du, et al., “Large-scale thin CsPbBr3 single-crystal film grown on sapphire via chemical vapor deposition: Toward laser array application,” ACS Nano 14(11), 15605–15615 (2020). [CrossRef]
22. Q. Li, C. Li, Q. Y. Shang, et al., “Lasing from reduced dimensional perovskite microplatelets: Fabry-Pérot or whispering-gallery-mode?” J. Chem. Phys. 151(21), 211101 (2019). [CrossRef]
23. Q. Y. Shang, C. Li, S. Zhang, et al., “Enhanced optical absorption and slowed light of reduced-dimensional CsPbBr3 nanowire crystal by exciton-polariton,” Nano Lett. 20(2), 1023–1032 (2020). [CrossRef]
24. S. J. Cheng, Z. Qiao, Z. Wang, et al., “Single mode lasing from CsPbBr3 microcrystals fabricated by solid state space-confined growth,” Adv. Opt. Mater. 11(15), 2203133 (2023). [CrossRef]
25. Y. Wang, M. Zhi, Y.-Q. Chang, et al., “Stable, ultralow threshold amplified spontaneous emission from CsPbBr3 nanoparticles exhibiting trion gain,” Nano Lett. 18(8), 4976–4984 (2018). [CrossRef]
26. Y. Q. Shi, R. X. Li, G. X. Yin, et al., “Laser-induced secondary crystallization of CsPbBr3 perovskite film for robust and low threshold amplified spontaneous emission,” Adv. Funct. Mater. 32(49), 2207206 (2022). [CrossRef]
27. A. Balena, A. Perulli, M. Fernandez, et al., “Temperature dependence of the amplified spontaneous emission from CsPbBr3 nanocrystal thin films,” J. Phys. Chem. C 122(10), 5813–5819 (2018). [CrossRef]
28. Z. P. Hu, Z. Z. Liu, Y. Bian, et al., “Enhanced two-photon-pumped emission from in situ synthesized nonblinking CsPbBr3/SiO2 nanocrystals with excellent stability,” Adv. Opt. Mater. 6(3), 1700997 (2018). [CrossRef]
29. H. L. Zhang, L. Yuan, Y. Chen, et al., “Amplified spontaneous emission and random lasing using CsPbBr3 quantum dot glass through controlling crystallization,” Chem. Commun. 56(19), 2853–2856 (2020). [CrossRef]
30. D. D. Yan, T. C. Shi, Z. G. Zang, et al., “Ultrastable CsPbBr3 perovskite quantum dot and their enhanced amplified spontaneous emission by surface ligand modification,” Small 15(23), 1901173 (2019). [CrossRef]
31. M. L. D. Giorgi, F. Krieg, M. V. Kovalenko, et al., “Amplified spontaneous emission threshold reduction and operational stability improvement in CsPbBr3 nanocrystals films by hydrophobic functionalization of the substrate,” Sci. Rep. 9(1), 17964 (2019). [CrossRef]
32. H. J. He, E. Ma, X. Y. Chen, et al., “Single crystal perovskite microplate for high-order multiphoton excitation,” Small Methods 3(12), 1900396 (2019). [CrossRef]
33. D. Kim, H. Ryu, S. Y. Lim, et al., “On the origin of room-temperature amplified spontaneous emission in CsPbBr3 single crystals,” Chem. Mater. 33(18), 7185–7193 (2021). [CrossRef]
34. C. Y. Zhao, W. M. Tian, J. X. Liu, et al., “Stable two-photon pumped amplified spontaneous emission from millimeter-sized CsPbBr3 single crystals,” J. Phys. Chem. Lett. 10(10), 2357–2362 (2019). [CrossRef]
35. S. Toso, D. Baranov, C. Giannini, et al., “Wide-angle x-ray diffraction evidence of structural coherence in CsPbBr3 nanocrystal superlattices,” ACS Mater. Lett. 1(2), 272–276 (2019). [CrossRef]
36. L. Zhang, Q. X. Zeng, K. Wang, et al., “Pressure-induced structural and optical properties of inorganic halide perovskite CsPbBr3,” J. Phys. Chem. Lett. 8(16), 3752–3758 (2017). [CrossRef]
37. Q. L. Jiang, X. Q. Zeng, N. Wang, et al., “Electrochemical lithium doping induced property changes in halide perovskite CsPbBr3 crystal,” ACS Energy Lett. 3(1), 264–269 (2018). [CrossRef]
38. B. Hua, J. Motohisa, Y. Kobayashi, et al., “Single GaAs/GaAsP coaxial core-shell nanowire lasers,” Nano Lett. 9(1), 112–116 (2009). [CrossRef]
