Recent progress on optical properties of double perovskite phosphors

Double perovskite materials have been studied in detail by many researchers, as their magnetic and electronic properties can be controlled by the substitution of alkaline earth metals or lanthanides in the A site and transition metals in the B site. Here we report the temperature-driven, p–n-type conduction switching assisted, large change in thermopower in La3+-doped Sr2TiFeO6-based double perovskites. Stoichiometric compositions of LaxSr2−xTiFeO6 (LSTF) with 0 ⩽ x ⩽ 0.25 were synthesized by the solid-state reaction method. Rietveld refinement of room-temperature XRD data confirmed a single-phase solid solution with cubic crystal structure and space group. From temperature-dependent electrical conductivity and Seebeck coefficient (S) studies it is evident that all the compositions underwent an intermediate semiconductor-to-metal transition before the semiconductor phase reappeared at higher temperature. In the process of semiconductor–metal–semiconductor transition, LSTF compositions demonstrated temperature-driven p–n-type conduction switching behavior. The electronic restructuring which occurs due to the intermediate metallic phase between semiconductor phases leads to the colossal change in S for LSTF oxides. The maximum drop in thermopower (ΔS ~ 2516 µV K−1) was observed for LSTF with x = 0.1 composition. Owing to their enormous change in thermopower of the order of millivolts per kelvin, integrated with p–n-type resistance switching, these double perovskites can be used for various high-temperature multifunctional device applications such as diodes, sensors, switches, thermistors, thyristors, thermal runaway monitors etc. Furthermore, the conduction mechanisms of these oxides were explained by the small polaron hopping model.

The toxicity of lead ions in halide perovskite absorbing materials is the main bottleneck for practical application. To replace the traditional lead halide perovskites by environmental friendly double perovskite, computational tools based on density functional theory were employed to predict the intrinsic properties of potential double perovskites to efficiently and rapidly find more double perovskites with properties suitable for optoelectronic applications. Screening homovalent alternatives for B and X‐site ions in vacancy‐ordered double perovskite Cs2BX6 for solar cell applications and photocatalyst was done using Perdew–Burke–Ernzerhof and Heyd–Scuseria–Ernzerhof functional with spin‐orbit coupling. Three empirical factors and formation enthalpy were used to evaluate the stability of 30 materials at different temperatures. Finally, the Cs‐based vacancy‐ordered double perovskites with suitable bandgap for optoelectronic applications can thus be obtained. Using computational techniques, this study can also provide theoretical guidance for the rational design of possible double perovskite materials with improved photocatalytic characteristics.image

All-inorganic double-metal perovskite materials have recently gained much attention due to their three dimensionality (3D) and non-toxic nature to replace lead-based perovskite materials. Among all those double perovskite materials, theoretical works have demonstrated that Cs2 AgBiBr6 shows high stability and possesses a suitable band gap for solar-cell applications. However, the film-forming ability of Cs2 AgBiBr6 is found to be the utmost challenge hindering its development in thin-film solar-cell devices. In this work, a high-quality Cs2 AgBiBr6 film with ultra-smooth morphology, micro-sized grains, and high crystallinity is realized via anti-solvent dropping technology and post-annealing at high temperature. After optimization, the first example of an inverted planar heterojunction solar-cell device based on Cs2 AgBiBr6 exhibits a power conversion efficiency of 2.23 % with VOC =1.01 V, JSC =3.19 mA/cm2 , and FF=69.2 %. Besides, the device shows no hysteresis and a high stability.

Theoretical pressure-tuning bandgaps of double perovskites A2(BB’) X6 for photo-voltaics

First principles study on electronic, magnetic and optical properties of Gd2NiMnO6

Dielectric, electrochemical and magnetic properties of the hydrothermally synthesized double perovskite La2NiMnO6 for energy storage applications

First principle insights on mechanical, electronic and optical properties of direct bandgap material Cs2KScX6 (X=Cl, Br and I) for optoelectronic applications

Due to their notable antimicrobial activity and optical properties, Schiff base ligands, along with their lanthanide and transition metal complexes, have seen extensive use in various applications. However, despite their potential, a comprehensive investigation into lanthanide and transition metal complexes using the same Schiff base ligand has not been reported to date. In this study, coordination compounds of lanthanide and transition metal ions were synthesized from the Schiff base ligand salicylaldehyde‐dipropylenetriamine. These complexes were characterized by elemental analysis, 1H and 13C NMR, mass spectroscopy, Fourier‐transform infrared spectroscopy ultraviolet–visible spectroscopy (UV–Vis), fluorescence spectroscopy, molar conductivity measurements, and thermogravimetric studies. Furthermore, the molecular structure of the Co (II) complex was determined by means of X‐ray crystallography. Thermogravimetric studies illustrated endothermic and non‐spontaneous degradation pathways of the complexes. UV–Vis spectra showed a new absorption band attributed to the ligand‐to‐metal charge transfer peak supporting the complexation between the ligand and metals. The lanthanide complexes exhibited distinctive luminescence emissions in the Sm (III), Tb (III), and Eu (III) complexes. This observation suggests that the ligand possesses the capability to absorb and efficiently transfer energy to the metal center of these lanthanide ions, thereby resulting in their characteristic luminescent properties. Additionally, antimicrobial investigations revealed that transition metal complexes generally exhibited antimicrobial activity against both gram‐positive and gram‐negative bacterial strains compared to lanthanide metal complexes, in most cases. However, it is noteworthy that the Dy (III) complex displayed the lowest minimum inhibitory concentration and minimum biocidal concentration values of 16 μg/ml against Staphylococcus epidermidis, indicating its potential as a candidate for the treatment of this pathogenic bacterium. The main purpose of this article is to investigate the variations in the synthesis and characterization of lanthanide and transition metal complexes utilizing the same Schiff base ligand suitable for applications in the pharmaceutical industry and optical material sciences.

In the field of perovskite solar cells, explorations of new lead-free all-inorganic perovskite materials are of great interest to address the instability and toxicity issues of lead-based hybrid perovskites. Recently, copper-antimony-based double perovskite materials have been reported with ideal band gaps, which possess great potential as absorbers for photovoltaic applications. Here, we synthesize Cs2CuSbCl6 double perovskite nanocrystals (DPNCs) at ambient conditions by a facile and fast synthesis method, namely, a modified ligand-assisted reprecipitation method. We choose methanol as a solvent for precursor salts as it is less toxic and easily removed in contrast to widely used dimethylformamide. Our computational structure search shows that the Cs2CuSbCl6 structure containing alternating [CuCl6]5− and [SbCl6]3− octahedral units is a metastable phase that is 30 meV/atom higher in energy compared to the ground state structure with [CuCl3]2− and [SbCl6]3− polyhedra. However, this metastable Cs2CuSbCl6 double perovskite structure can be stabilized through solution-based nanocrystal synthesis. Using an anion-exchange method, Cs2CuSbBr6 DPNCs are obtained for the first time, featuring a narrow bandgap of 0.9 eV. Finally, taking advantage of the solution processability of DPNCs, smooth and dense Cs2CuSbCl6 and Cs2CuSbBr6 DPNC films are successfully fabricated.

A first principle comparison of arsenic-based double halide perovskite materials for photovoltaic and optoelectronic application

Anomalous magnetic behaviors of double perovskite R2CrFeO6 (R = rare earth elements) predicted by first-principles calculations

Experimental and theoretical studies of synthesized <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si10.svg"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="italic">Bi</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi mathvariant="italic">NiCrO</mml:mi></mml:mrow><mml:mrow><mml:mn>6</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> double perovskite material

The double perovskite materials are exceptional for energy applications due to their non-toxic, efficient, and eco-friendly nature. Here, we comprehensively addressed the electronic, optical, and thermoelectric characteristics of double perovskites Tl2PtX6 (X = Cl, Br, I). The tolerance factor and formation energy, an important criterion for the existence of structural and thermodynamic stability are computed. The strong p-d hybridization between cations (Pt) and anions (Cl, Br, I) tune the band gaps from 2.83 eV, 2.18 eV, and 1.35 eV. The diminution of band gap due to replacement of Cl to I anions shifts the absorption to visible region. For detailed analysis, the optical behavior is explored from 0–5 eV in terms of absorption, optical loss, dielectric constants, and reflection of light from materials under study. Furthermore, thermoelectric behavior has been examined by power factor, Seebeck coefficient, and figure of merit. The high figure of merit and ultralow lattice thermal conductivity increased their significance for thermoelectric applications.

Layered double perovskite materials of type AA’B2O5+δ (where A is rare earth element and A’ is alkaline earth element) are suggested as potential candidate for a cathode in solid oxide fuel cells (SOFCs) because of their distinct oxygen-deficient perovskite-related structure, higher oxygen ion diffusion rate and surface exchange coefficient following a stacking sequence of /BO/AO/BO/A’O/BO/... [1,2]. In general, the layered double perovskites with rare earth metals at A-site, Ba at A’-site and Co at B-site have received much attention due to high oxygen vacancy concentration, high electronic conductivity and high catalytic activity. Presence of Pr, Gd and Nd at the A-site of the structure are observed to improve electronic conductivities, oxygen self-diffusion, oxygen exchange, resulting into reduced area specific resistances (ASRs) of the electrode [1-3]. In this study, Density Functional theory (DFT) calculations are performed for NdBaCo2O5+δ (NBCO) and Sr-doped at NBCO to study and compare oxygen vacancy formation energies in different planes and surface energies for different terminating surfaces of the NBCO material and access the role of Sr doping.Using DFT with Hubbard U correction of 3.3 eV for Co, oxygen vacancy formation energies in Ba/O, Co/O and Nd/O planes of bulk are observed as 245.88 KJ/mol, 144.93 KJ/mol and 72.13 KJ/mol respectively. DFT calculations predicted difficulty in creating oxygen vacancies in Ba/O plane as compared to Co/O and Nd/O plane of bulk NBCO. On doping one fourth and half of Ba with Sr resulted into a decrease in oxygen vacancy formation energies in BaSr/O plane of bulk i.e., less energy is needed to remove oxygen in BaSr/O plane. Further the Sr-doping at A’-site have shown decrease in lattice parameters. The energetics of surface with terminating surfaces Ba/Co, Nd/Co, Co/Ba and Co/Nd in (001) direction revealed Ba/Co and Co/Nd surface as the stable terminal surfaces. The trend of surface energies revealing Ba/Co surface as most stable in NBCO material is found to be similar as predicted in our previous studies on PrBaCo2O5+δ, GdBaCo2O5+δ[4,5]. Different energetics of the surfaces play an important role in the electrochemical performance of the cathode material. In conclusion, Sr-doping at A’-site in is likely to improve the energetics of oxygen vacancy formation in the BaSr/O planes as compared to undoped NBCO material.

Double perovskite materials have emerged as key players in the realm of advanced materials due to their unique structural and functional properties. This research mainly focuses on the synthesis and comprehensive characterization of Ba2CoWO6 double perovskite nanopowders utilizing a high-temperature conventional solid-state reaction technique. The successful formation of Ba2CoWO6 powders was confirmed through detailed analysis employing advanced characterization techniques. Rietveld refinement of X-ray diffraction (XRD) and Raman data established that Ba2CoWO6 crystallizes in a cubic crystal structure with the space group Fm-3m, indicative of a highly ordered perovskite lattice. The typical crystallite size, approximately 65 nm, highlights the nanocrystalline nature of the material. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) discovered a distinctive morphology characterized by spherical shaped particles, suggesting a complex particle formation process influenced by synthesis conditions. To probe the electronic structure, X-ray Photoelectron Spectroscopy (XPS) identified cobalt and tungsten valence states, critical for understanding dielectric properties associated with localized charge carriers. The semiconducting character of the synthesized Ba2CoWO6 nanocrystalline material was confirmed through UV-Visible analysis, which revealed an energy bandgap value of 3.3 eV, which aligns well with the theoretical predictions, indicating the accuracy and reliability of the experimental results. The photoluminescence spectrum exhibited two distinct emissions in the blue-green region. These emissions were attributed to the transitions 3P0→3H4, 3P0→3H5, and 3P0→3H6, primarily resulting from the contributions of Ba2+ ions. The dielectric characteristics of the compound were analyzed across a different range of frequencies, spanning from 1 kHz to 1 MHz. Magnetic characterization using Vibrating Sample Magnetometry (VSM) revealed antiferromagnetic behavior of Ba2CoWO6 ceramics at room temperature, attributed to super-exchange interactions between Co3+ and W5+ ions mediated by oxygen ions in the perovskite lattice. Additionally, first-principles calculations based on the Generalized Gradient Approximation (GGA+U) with a modified Becke–Johnson (mBJ) potential were employed to gain a deeper understanding of the structural and electronic properties of the materials. This approach involved systematically varying the Hubbard U parameter to optimize the description of electron correlation effects. These results deliver an extensive understanding of the structural, optical, morphological, electronic, and magnetic properties of Ba2CoWO6 ceramics, underscoring their potential for electronic and magnetic device applications.