Abstract
CsPbBr3 and Cs4PbBr6 perovskite powders have been synthesized through a relatively simple low-temperature and low-cost method. Nanocrystalline films have also been deposited from solutions with four different molar compositions of binary salt precursors. Optical absorption, emission and excitation spectra have been performed in the UV-visible spectral range while X-ray diffraction (XRD) has been recorded to characterize the nanocrystal morphology for the different molar compositions. A preferential orientation of crystallites along the (024) crystalline plane has been observed as a function of the different deposition conditions in films growth. All the crystals show an absorption edge around 530 nm; Tauc plots of the absorption returned bandgaps ranging from 2.29 to 2.35 eV characteristic of CsPbBr3 phase. We attribute the UV absorption band peaked at 324 nm to the fundamental band-to-band transition for Cs4PbBr6. It was observed that the samples with the most ordered Cs4PbBr6 crystals exhibited the most intense emission of light, with a bright green emission at 520 nm, which are however due to the luminescence of the inclusion of CsPbBr3 nanoclusters into the Cs4PbBr6. The latter shows instead an intense UV emission. Differently, the pure CsPbBr3 powder did not show any intense fluorescent emission. The excitation spectra of the green fluorescent emission in all samples closely resemble the CsPbBr3 absorption with the peculiar dip around 324 nm as expected from density of state calculations reported in the literature.
Highlights
Calcium titanium oxide mineral (CaTiO3) was the first crystal to be named perovskite
Microcrystal investigate the distribution of the different crystalline phases
3a shows the spectra the investigate the distribution of the different crystalline phases
Summary
Calcium titanium oxide mineral (CaTiO3) was the first crystal to be named perovskite. Its name has been extended to a class of compounds which have the same type of crystal structure, known as the perovskite structure. Many different cations can be embedded in this structure, allowing the development of diverse engineered materials. With the chemical formula An BX(2+n) , where A and B are respectively the monovalent and divalent (Pb, Sn) cations and X is a monovalent anion (Cl, Br, I), are a large family of materials with a wide range of compositional and structural flexibilities [1]. Perovskites are typically divided into two main categories depending on the chemical component of the cation A. When A is an organic cation (e.g., the well-known methyl ammonium MA = CH3 NH3 + )
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