Exploring spin-polarized structural, ferromagnetic, optoelectronic, thermodynamic, and mechanical attributes of lead-free Cs 2 GdAuX 6 (X = Br/I) double perovskites for spintronics and green energy applications

In recent years, inorganic halide-based non-toxic double perovskite (DP) has emerged as a promising group of materials that are more stable than hybrid lead-based organic and inorganic perovskite materials for green energy applications. In this work, first time we report the synthesis of a new inorganic non-toxic halide-based double perovskite Cs2AlBiCl6 by a simple room-temperature synthesis technique. The structural properties of the synthesized material has been observed by using X-Ray diffraction (XRD). The observed peaks of XRD were found to be in good agreement with the reference data. To envisage the photo physical properties, we have done the photoluminescence (PL) spectroscopy of the synthesized material at low temperature (19 K) and high temperature (300 K). It is clear from the PL spectra that the main peak has been observed around 424 nm corresponding to 2.9 eV energy which also confirms the luminescent behavior of the material. The observed peak in the PL spectra is due to phonon-assisted carrier recombination of the excitons. Also, the PL intensity at low temperature (19K) is high as compared to high temperature (300K) due to a decrease in carrier recombination rate with an increase in temperature. This novel work opens a new path for the synthesis of non-toxic double perovskite materials for photovoltaic and green energy applications.

First-principles investigations of the mechanically and thermodynamically stable potassium-based double perovskites K2TlAsX6 (X = Cl, Br) for optoelectronic and renewable applications

Explored the potential of Rb2SeX6 (X=Cl, Br) double perovskites for energy harvesting devices: A DFT study

Study of Mechanical, Optoelectronic, and thermoelectric aspects of lithium-based double perovskites Li2AgSbX6 (X=Cl, Br, I) for energy harvesting applications

The effect of diamagnetic dilution of the Fe sublattice on the structural and magnetic properties of the double perovskite ${\mathrm{Sr}}_{2}{\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}\mathrm{Re}{\mathrm{O}}_{6}$ $(0<x<0.7)$ has been explored by means of x-ray structural analysis, magnetometry, M\"ossbauer spectroscopy, and band structure calculations. The end member of the solid solution series, ${\mathrm{Sr}}_{2}\mathrm{Ga}\mathrm{Re}{\mathrm{O}}_{6}$, was predicted to be a half-metallic ferromagnet based on ab initio band structure calculations using the WIEN2k software package. Because the Re-containing double perovskites, like the parent compound ${\mathrm{Sr}}_{2}\mathrm{Fe}\mathrm{Re}{\mathrm{O}}_{6}$, rarely exhibit antisite disorder, the appearance of increasing amounts of antisite disorder in ${\mathrm{Sr}}_{2}{\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}\mathrm{Re}{\mathrm{O}}_{6}$ $(0<x<0.7)$ is unexpected. Although the amount of antisite disorder increases with increasing Ga content, it also depends on the sample preparation history. For $0<x<0.4$ only a tetragonal, magnetically ordered phase was detected by x-ray structural analysis as well as M\"ossbauer analysis. A phase separation into a tetragonal and a cubic phase for $x\ensuremath{\geqslant}0.4$ is detected by x-ray structural analysis accompanied by the observation of a magnetically ordered and a paramagnetic phase in the corresponding M\"ossbauer spectra. Below 20% Ga content, Ga statistically dilutes the -Fe-O-Re-O-Fe- double-exchange pathways. Phase separation begins at 20% Ga substitution; between 20% and 40% of Ga content, the paramagnetic Ga-based phase does not contain any Fe. The Fe-containing, paramagnetic cubic phases which can be detected by M\"ossbauer spectroscopy first appear for $x=0.4$.

Investigating structural, phonons, optoelectronics, and thermodynamic properties of lead-free double perovskites of A-site cation ordering in LiXTl2Cl6 (X= Sc and Y) compounds for green energy applications

Theoretical investigations of double perovskites Rb2YCuX6 (X =Cl, F) for green energy applications: DFT study

Hybrid lead halide perovskites have been considered as promising candidates for a large variety of optoelectronic applications. By exploring novel combinations of lead-free double perovskite halides, it is possible to find a suitable replacement for poisonous lead halide perovskites, enhancing electronic and optical response for their application as optically-influenced resistive switching random access memory (RRAM). In this work, the structural, mechanical, elastic, electronic, optical, and thermoelectric characteristics of lead-free double halide perovskites were investigated by Vienna ab initio simulation package (VASP) to explore their role in RRAM. From the analysis of mechanical constraints, it is clear that all three composites of Cs2CaSnX6 (X = Cl, Br, I) are mechanically stable and ductile in nature. The electronic bandgap with and without spin–orbit coupling (SOC), and total and sub-total density of states (TDOS, sub-TDOS) have been calculated using the Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) potentials. The observed direct band gaps of 3.58 eV, 3.09 eV, and 2.60 eV for Cs2CaSnCl6, Cs2CaSnBr6, and Cs2CaSnI6, respectively, reveal the suitability of these specified composites as resistive switching material for RRAM devices. Additionally, the optical characteristics, such as complex refractive index, absorption coefficient, and reflectivity of the compounds under consideration have been calculated under the action of incident photons of 0 to 14 eV energy. The thermoelectric properties of Cs2CaSnX6 (X = Cl, Br, I) double perovskite halide were computed and analyzed with the help of the BoltzTraP Code.

A2LiGaI6 (A = Cs, Rb): New lead-free and direct bandgap halide double perovskites for IR application

Density functional study on electronic properties of transition metal-based vacancy-ordered halide perovskites

Using density functional theory, we investigated the structural, vibrational, and electronic properties of A2LnRuO6 (A = Ba, Ca; Ln = Eu, Dy) double perovskite oxides using GGA and GGA+U exchange-correlation approximations. Ba2LnRuO6 double perovskites exhibit a structure with cubic ( Fm3¯m ) symmetry, whereas Ca2LnRuO6 compounds have monoclinic (P21/n) symmetry. Raman spectroscopy analysis shows stability and the presence of A1g , E g and 2F2g modes for Ba2LnRuO6, while for Ca2LnRuO6, the observed Raman active modes are A g and B g . A2LnRuO6 shows semiconducting nature with an electronic band gap in the range of 1.3 eV-3.27 eV with GGA+U calculations. The spin-polarized calculations indicate the presence of strong magnetic behaviour with magnetic moment equal to 3 μ B /unit cell for Ba2LnRuO6 and 6 μ B /unit cell for Ca2LnRuO6. The spin-up and spin-down states show different band gap values so these compounds can be useful for applications in spintronics and magnetic memory devices.

The physical, magneto-electronic, optical, and transport characteristics of the noble inorganic f-electron-based double perovskite Sr2PrSnO6 are analyzed, with first-principles density functional theory (DFT) computation for advanced spintronics, optoelectronic, and magneto-RAM applications. The DFT-optimized tolerance factor, formation enthalpy (ΔHf), and structural parameters confirm the ferromagnetic state’s stability in the cubic phase. The density of states profiles and electronic energy band from generalized-gradient approximation + Perdew–Berke–Ernzerhof demonstrate Sr2PrSnO6 half-metallic behavior, exhibiting maximal spin polarization at the Fermi level and dominance by the Pr-f orbital on the event of spin-polarized band edge behavior. Thereby, the Pr-Sn-based double perovskite resembles ferromagnetic behavior, where the total magnetic moment is 3.6 μB, primarily originating from the Pr and Sn atoms at the B-site. The optical properties of Sr2PrSnO6, including high UV absorption, dielectric function, low reflectivity, high refractive index at lower energies, and optical conductivity, indicate its potential for optoelectronic devices. The elastic parameters indicate that Sr2PrSnO6 is ductile, enhancing its suitability for use in the practical industry. Finally, thermodynamic and transport properties were examined for temperatures ranging from 100 to 1000 K. The analysis of transport parameters, namely the Seebeck coefficient, power factor, and thermoelectrical conductivity, shows the material’s enhanced performance at higher temperatures, providing insights into potential applications in spintronics and advanced thermoelectric technologies.

Computational study of Rubidium-Rb based cubic Rb2TlCoF6 double perovskite material for photocatalytic water degradation applications: A DFT investigations

Recently, the unique double perovskites are continuously being used for solar cells and thermoelectric applications because of stable structures and high energy conversion efficiency. We addressed the optical and transport characteristics of X2GeI6 (X = K, Rb, Cs) by first-principle calculations. The tolerance factor confirms the structural stability. The computed band gaps 1.27 eV (K2GeI6), 1.24 eV (Rb2GeI6), and 1.13 eV (Cs2GeI6) plunge the maximum absorption in visible light zone. The first absorption bands 459 to 826 nm for K2GeI6, 477 to 885 nm for Rb2GeI6, and 653 to 992 nm for Cs2GeI6 are outstanding for visible light solar cells. While the second absorption bands are for other optoelectronic devices like surgical equipment. The optical characteristics are debated by frequency-dependent dielectric constants (ε1, ε2), refractive index, and absorption coefficient. Thermoelectric performance is evaluated by large values of power factor and ultralow values of thermal conductivity for both n- and p-type of charge carriers. Highlights An alternative of organic-inorganic and Pb based perovskites Ideal band gaps 1.27 eV, 1.24 eV, and 1.13 eV of K2GeI6, Rb2GeI6, and Cs2GeI6 for solar cells Absorption in the visible region increases their potential for solar cells. Observation of ultralow lattice thermal conductivity.

Crystal structure, mechanical, electronic, optical and thermoelectric characteristics of Cs2MCl6 (M = Se, Sn, Te and Ti) cubic double perovskites