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Ellipsometry - Principles and Techniques for Materials Characterization || Spectroscopic Ellipsometry Study of Organic-Inorganic Halide: FAPbIxBr3?x Perovskite Thin Films by Two-Step Method
摘要： Spectroscopic ellipsometry (SE) was used to investigate the role of isopropyl alcohol (IPA) solvent in the synthesis of organic-lead-halide perovskite CH(NH2)2PbIxBr3?x [FAPbIxBr3?x] thin films including the effect of I/Br composition ratio by the two-step reaction of an amorphous (a-)PbIxBr2?x layer and FAIxBr1?x solution diluted in IPA. An optical dispersion model was developed to extract the complex refractive index N (=n + ik), optical transition, and film thickness of FAPbIxBr3?x perovskites by SE analysis at different I/Br composition ratio as a function of immersion time in a solution of FAIxBr1?x diluted in IPA. SE combined with X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) revealed that Br incorporation into films promoted the densification of FAPbIxBr3?x perovskite network along with increased film thickness and volume fraction of void. IPA promoted film crystallization of a-PbIxBr2?x accompanied by the formation of surface roughness, grain boundaries, and voids, followed by enhanced diffusion of FAIxBr1?x into the grain boundaries/voids in the mesoporous crystallized PbIxBr2?x network. These processes contribute synergistically to the growth of the perovskite structure.
关键词： growth mechanism,two-step reaction,ellipsometry,role of isopropyl alcohol (IPA) solvent,organic-lead-halide perovskite
更新于2025-09-09 09:28:46
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Room-Temperature Synthesis of Cesium Lead Halide Perovskite Nanorods
摘要： Low-dimensional materials attract much attention because of their unique and outstanding properties in optical and electronic products, giving a promising class of materials for optoelectronic applications. A facile synthesis method of CsPbBr3 nanorods (NRs) was presented in this paper. The nanorods have a one-dimensional (1D) scale, a high photoluminescence quantum yield (PLQY, 60%) and a narrow FWHM. By tuning the ratio of organic ligands, the CsPbBr3 NRs with the diameter of less than 20 nm and length up to several hundred nanometers were obtained. Moreover, because of the quantum confinement effects, a large blue-shift have happened in PL spectra. A light-emitting diode (LED) device was fabricated with our synthesized CsPbBr3 NRs. The LED device showed a strong green emission. All of these shows the ability of halide perovskite nanocrystals for applications on photoelectron, such as optical communication, display, lightning and so on.
关键词： formation mechanism,cesium lead halide perovskite nanorods,light-emitting diode
更新于2025-09-09 09:28:46
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Dimensionality engineering of hybrid halide perovskite light absorbers
摘要： Hybrid halide perovskite solar cells were first demonstrated in 2009 with cell efficiency quickly soaring from below 10% to more than 23% in a few years. Halide perovskites have the desirable processing simplicity but are very fragile when exposed to water and heat. This fragility represents a great challenge for the achievement of their full practical potential in photovoltaic technologies. To address this problem, here we review the recent development of the mixed-dimensional perovskites, whereby the trade-off between power conversion efficiency and stability of the material can be finely tuned using organic amine cations with different sizes and functionalities.
关键词： hybrid halide perovskite,organic amine cations,stability,mixed-dimensional perovskites,solar cells,power conversion efficiency
更新于2025-09-09 09:28:46
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Binary metal zinc-lead perovskite built-in air ambient: Towards lead-less and stable perovskite materials
摘要： Organo-metal halide perovskites are promising new-generation photovoltaic materials owing to their efficient electrical/optical characteristics. Despite having high efficiency, perovskites are toxic due to the presence of lead and instable in air ambient. Therefore, the toxicity and instability call for more efforts in this area. Here, methylammonium-zinc-lead iodide (MAZn0.2Pb0.8I3) is synthesized in air ambient as lead-less and more stable perovskite material for applying as the active layer of solar cells. 1.65 eV optical band gap and 51 nm minority carrier diffusion length (Ldiff) have been obtained with the help of UV–Visible spectroscopy (UV–Vis) and steady-state photocarrier grating (SSPG) technique respectively. Structural, chemical bonding and surface studies are done by X-ray powder diffraction (XRPD), Fourier-transform infrared spectroscopy (FTIR) and Field Emission Scanning Electron Microscope (FESEM) respectively. The sample has been stored in dark air ambient with average relative humidity of 45% at room temperature (27 °C) for 60 days and the properties of 60 days aged sample is investigated and compared with characteristics of 60 days aged MAPbI3. The results confirm MAZn0.2Pb0.8I3 is more stable than MAPbI3.
关键词： Lead-less organo-zinc-lead halide perovskite,Synthesis in air ambient,Stability
更新于2025-09-09 09:28:46
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Stabilizing RbPbBr3 Perovskite Nanocrystals through Cs+ Substitution
摘要： The ABX3-type halide perovskite nanocrystals (NCs) have been a hot topic recently due to their fascinating optoelectronic properties. It has been demonstrated that A-site ion has an impact on the photophysical and chemical properties, such as optical bandgap and chemical stability. The pursuit of halide perovskite materials with diversified A-site species would deepen the understanding on the structure-property relationship of the perovskite family. Herein, we attempt to synthesis the Rb-based perovskite NCs. We discover that the partial substitution of Rb+ by Cs+ helps to stabilize the orthorhombic RbPbBr3 NCs at low temperature, which otherwise can only be obtained at high temperature. The inclusion of Cs+ into RbPbBr3 lattice results in highly photoluminescent Rb1-xCsxPbBr3 NCs. With the increasing amount of Cs+, the bandgap of Rb1-xCsxPbBr3 NCs decreases, leading to the red shift of photoluminescence peak. The Rb1-xCsxPbBr3 NCs (x=0.4) show good stability in ambient condition. This work demonstrates the high structural flexibility and tunability of halide perovskite materials through A-site cation substitution strategy and sheds light on the optimization of perovskite materials for high-performance optoelectronic devices.
关键词： halide perovskite,phase stabilization,cation substitution,RbPbBr3,nanocrystals
更新于2025-09-04 15:30:14
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X-ray study of anisotropically shaped metal halide perovskite nanoparticles in tubular pores
摘要： Recently, we have reported that metal halide perovskite nanoparticles formed in nanoporous alumina and silicon thin films exhibit blue shifted photoluminescence due to spatial confinement, thus allowing for color tuning of the emission by varying the pore size. While perovskite nanoparticles grown in nanoporous alumina films have been integrated into LEDs, similar approaches have failed with silicon. Here, we report the results of investigating the structure of the alumina pore system and the perovskite crystallites forming within. We use two x-ray diffraction techniques, namely, small-angle x-ray scattering (SAXS) and high-energy microbeam wide-angle x-ray scattering (WAXS). SAXS reveals that the alumina pore system diffracts like regularly arranged tubes with the average diameter and nearest neighbor distance of 12 nm and 20 nm, respectively. High-energy microbeam WAXS shows that perovskite nanoparticles within the nanoporous alumina have a distinctly anisotropic shape with the average particle length along and perpendicular to the pore axis of 26 nm and 13 nm, respectively. In contrast, no shape anisotropy has been detected for nanoparticles inside the silicon pores in a previous study. This suggests that utilizing nanoporous alumina has a twofold advantage. First, the tubular alumina pores, spanning the entire insulating film, offer percolated paths for the perovskite to fill. Second, the elongation of the nanoparticles in the tubular alumina pores can be expected to aid device performance as the length of the nanoparticles approaches the active layer thickness (ca. 40 nm) of LEDs, while the small diameter of the crystallites accounts for the observed blue shifted emission.
关键词： LEDs,anisotropic shape,nanoporous alumina,SAXS,WAXS,nanoparticles,metal halide perovskite
更新于2025-09-04 15:30:14