Search Results (1,543)

The appearance of spin-induced ferroelectric polarization in the so-called type-II multiferroic materials has received a lot of attention. The nature and mechanisms of such polarization were intensively studied using perovskite rare-earth manganites, RMnO₃, as model systems. Later, multiferroic properties were discovered in some RFeO₃ perovskites and possibly in some RCrO₃ perovskites. However, R₂NiMnO₆ double perovskites have ferromagnetic structures that do not break the inversion symmetry. It was found recently that more complex magnetic structures are realized in A-site-ordered quadruple perovskites, RMn₃Ni₂Mn₂O₁₂. Therefore, they have the potential to be multiferroics. In this work, dielectric properties in magnetic fields up to 9 T were investigated for such perovskites as RMn₃Ni₂Mn₂O₁₂ with R = Ce to Ho and for BiMn₃Ni₂Mn₂O₁₂. The samples with R = Bi, Ce, and Nd showed no dielectric anomalies at all magnetic fields, and the dielectric constant decreases with decreasing temperature. The samples with R = Sm to Ho showed qualitatively different behavior when the dielectric constant started increasing with decreasing temperature below certain temperatures close to the magnetic ordering temperatures, T_N. This difference could suggest different magnetic ground states. The samples with R = Eu, Dy, and Ho still showed no anomalies on the dielectric constant. On the other hand, peaks emerged at T_N on the dielectric constant in the R = Sm sample from about 2 T up to the maximum available field of 9 T. The Gd sample showed peaks on dielectric constant at T_N between about 1 T and 7 T. Transition temperatures increase with increasing magnetic fields for R = Sm and decrease for R = Gd. These findings suggest the presence of magnetic-field-induced multiferroic states in the R = Sm and Gd samples with intermediate ionic radii. Dielectric properties at different magnetic fields are also reported for Lu₂NiMnO₆ for comparison. Full article

Perovskites (ABX₃) exhibit remarkable potential in optoelectronic conversion, catalysis, and diverse energy-related fields. However, the tunability of A, B, and X-site compositions renders conventional screening methods labor-intensive and inefficient. This review systematically synthesizes the roles of physical simulations and machine learning (ML) in accelerating perovskite discovery. By harnessing existing experimental datasets and high-throughput computational results, ML models elucidate structure-property relationships and predict performance metrics for solar cells, (photo)electrocatalysts, oxygen carriers, and energy-storage materials, with experimental validation confirming their predictive reliability. While data scarcity and heterogeneity inherently limit ML-based prediction of material property, integrating high-throughput computational methods as external mechanistic constraints—supplementing standardized, large-scale training data and imposing loss penalties—can improve accuracy and efficiency in bandgap prediction and defect engineering. Moreover, although embedding high-throughput simulations into ML architectures remains nascent, physics-embedded approaches (e.g., symmetry-aware networks) show increasing promise for enhancing physical consistency. This dual-driven paradigm, integrating data and physics, provides a versatile framework for perovskite design, achieving both high predictive accuracy and interpretability—key milestones toward a rational design strategy for functional materials discovery. Full article

The intrinsic structural stability of ABO₃ perovskite materials is a pivotal factor determining their efficiency and durability in photovoltaic applications. However, accurately predicting stability, commonly measured by the energy above hull metric, remains challenging due to the complex interplay of compositional, crystallographic, and electronic features. To address this challenge, we propose a streamlined hybrid machine learning framework that combines the sequence modeling capability of Long Short-Term Memory (LSTM) networks with the robustness of Random Forest regressors. A genetic algorithm-based feature selection strategy is incorporated to identify the most relevant descriptors and reduce noise, thereby enhancing both predictive accuracy and interpretability. Comprehensive evaluations on a curated ABO₃ dataset demonstrate strong performance, achieving an $R^2$ of 0.98 on training data and 0.83 on independent test data, with a Mean Absolute Error (MAE) of 8.78 for training and 21.23 for testing, and Root Mean Squared Error (RMSE) values that further confirm predictive reliability. These results validate the effectiveness of the proposed approach in capturing the multifactorial nature of perovskite stability while ensuring robust generalization. This study highlights a practical and reliable pathway for accelerating the discovery and optimization of stable perovskite materials, contributing to the development of more durable next-generation solar technologies. Full article

Perovskite solar cells (PSCs) have emerged as promising photovoltaic technologies owing to their high power conversion efficiency (PCE) and material versatility. Conventional optimization of PSC architectures largely depends on iterative experimental approaches, which are often labor-intensive and time-consuming. In this study, a data-driven modeling strategy is introduced to accelerate the design of efficient and mechanically robust PSCs. Seven supervised regression models were evaluated for predicting key photovoltaic parameters, including PCE, short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF). Among these, a stacking ensemble framework exhibited superior predictive accuracy, achieving an R² of 0.8577 and a root mean square error of 2.084 for PCE prediction. Model interpretability was ensured through Shapley Additive exPlanations(SHAP) analysis, which identified precursor solvent composition, A-site cation ratio, and hole-transport-layer additives as the most influential parameters. Guided by these insights, ten device configurations were fabricated, achieving a maximum PCE of 24.9%, in close agreement with model forecasts. Furthermore, multiscale mechanical assessments, including bending, compression, impact resistance, peeling adhesion, and nanoindentation tests, were conducted to evaluate structural reliability. The optimized device demonstrated enhanced interfacial stability and fracture resistance, validating the proposed predictive–experimental framework. This work establishes a comprehensive approach for performance-oriented and reliability-driven PSC design, providing a foundation for scalable and durable photovoltaic technologies. Full article

Recent advances in energy conversion technologies, especially solar-driven photocatalytic water splitting, are vital for satisfying the increasing global need for sustainable and clean energy. Perovskite oxides have attracted considerable attention among photocatalytic materials due to their tunable electronic structures, exceptional stability, and promise for effective hydrogen generation and environmental remediation. In this study, the optoelectronic and photocatalytic (PC) characteristics of ATiO₃ (A = Ca, Mg) perovskites, undoped and codoped with Se and Zr, have been analyzed using ab initio simulations based on the density functional theory (DFT). The calculated formation energies for codoped systems range from −1.01 to −3.32 Ry/atom, confirming their thermodynamic stability. Furthermore, band structure calculations indicate that the undoped compounds CaTiO₃ and MgTiO₃ possess indirect band gaps of 2.766 eV and 2.926 eV, respectively. In contrast, codoping alters the electronic properties by changing the band gap from indirect to direct and reducing its energy, resulting in the direct band gap values 2.153 eV, 1.374 eV, 2.159 eV, and 1.726 eV for the compounds ${{\mathrm{C}\mathrm{a}}_8\mathrm{T}\mathrm{i}}_7{\mathrm{Z}\mathrm{r}}_1{\mathrm{O}}_{23}{\mathrm{S}\mathrm{e}}_1$, ${{\mathrm{C}\mathrm{a}}_8\mathrm{T}\mathrm{i}}_6{\mathrm{Z}\mathrm{r}}_2{\mathrm{O}}_{22}{\mathrm{S}\mathrm{e}}_2$, ${{\mathrm{M}\mathrm{g}}_8\mathrm{T}\mathrm{i}}_7{\mathrm{Z}\mathrm{r}}_1{\mathrm{O}}_{23}{\mathrm{S}\mathrm{e}}_1$, and ${{\mathrm{M}\mathrm{g}}_8\mathrm{T}\mathrm{i}}_6{\mathrm{Z}\mathrm{r}}_2{\mathrm{O}}_{22}{\mathrm{S}\mathrm{e}}_2$, respectively. Additionally, this codoping improves light absorption and optical conductivity in the visible and ultraviolet ranges. These enhancements become increasingly evident with elevated dopant concentrations, leading to intensified light–matter interactions. Analysis of the band edge potentials reveals that the Se-/Zr-codoped CaTiO₃ compounds satisfy the necessary criteria for the photodissociation of water, conferring on them an ability to generate H₂ and O₂ under light irradiation. However, under different pH conditions, Se-/Zr-codoped MgTiO₃ is expected to perform better at higher pH levels, while Se-/Zr-codoped CaTiO₃ is more effective at lower pH levels. These findings highlight the promise of codoped materials for renewable energy applications, such as solar-driven hydrogen production and optoelectronic devices, with pH being a critical factor in enhancing their photocatalytic performance. Full article

In optical one-dimensional grating-on-layer planar structures, an optical resonance occurs when the incident light wave becomes phase-matched to a leaky waveguide mode excited in the layer underneath the grating by an appropriate tuning of the grating periodicity. Changing the refractive indices of the grating’s constituents, and/or thickness, changes the resonance frequency. In the case of a two-dimensional grating atop such a smooth layer, a similar and also cavity-mode resonance can occur. This idea has straightforward usage in diverse optical sensor applications. In this study, a novel guided-mode resonance sensor design for detecting glucose and hemoglobin in minute concentrations at a wide range of incidence angles is presented. In this design, materials of the grating, such as a polymer and cesium-lead halide with a perovskite crystal structure, are examined, which will allow flexible, low-cost fabrication by soft-lithography/imprint-lithography methods. The sensitivity, figure of merit, and quality factor are reported for one- and two-dimensional grating structures. The simulations performed are based on rigorous coupled-wave analysis. Optical resonance quality factor of ∼$5·{10}^5$ is achieved at oblique incidence for a structure comprising a one-dimensional grating etched in a poly-vinylidene chloride layer atop a silicon nitride waveguide layer on a substrate. Record values of the above-noted characteristics are achieved with a synergetic interplay of the materials, structural dimensions, incidence angle, polarization, and grating geometry. Full article

This study addresses the development of advanced anode materials for lithium-ion batteries by investigating the high-entropy perovskite La(Co_0.2Mn_0.2Fe_0.2Ni_0.2Cu_0.2)O₃. The material was synthesized via spray drying of aqueous metal nitrate solutions, followed by calcination at various temperatures (800 °C/1 h, 1000 °C/1 h, 1000 °C/2 h, 1100 °C/1 h) to optimize structural properties. Structural analysis using X-ray diffraction confirmed the formation of a single-phase perovskite in the sample calcined at 1100 °C for 1 h, while SEM/EDS revealed homogeneous elemental distribution. Electrochemical testing of the powders as anode materials in coin-type lithium-ion cells revealed a trend of slightly increasing capacity over 150 cycles, with capacity ultimately reaching 617 mAh g⁻¹, indicating progressive electrochemical activation. Although the samples share the same composition, variations in calcination conditions resulted in differences in capacity and cycling behavior. These results demonstrate that synthesis parameters critically influence the electrochemical performance of high-entropy perovskites. The findings suggest that such materials have potential as stable anodes for next-generation lithium-ion batteries, contributing to improved durability and efficiency in energy-storage technologies. Full article

Perovskite solar cells (PSCs) rarely report, on a single-device platform, concurrent gains in optoelectronic efficiency and buried-interface mechanical robustness—two prerequisites for flexible and roll-to-roll (R2R) integration. We engineered a nanoplate-structured fluorine-doped tin oxide (NP-FTO) front electrode that couples light management with three-dimensional interfacial anchoring, and we quantified both photovoltaic (PV) and nanomechanical metrics on the same device stack. Relative to planar FTO, the NP-FTO PSCs achieved PCE of up to 25.65%, with simultaneous improvements in Voc (to 1.196 V), Jsc (up to 26.35 mA cm⁻²), and FF (to 82.65%). Nanoindentation revealed a ~28% increase in reduced modulus and >70% higher hardness, accompanied by a ~32% reduction in maximum indentation depth, indicating enhanced load-bearing capacity consistent with the observed FF gains. The low-temperature, solution-compatible NP-FTO interface is amenable to R2R manufacturing and flexible substrates, offering a unified route to bridge high PCE with reinforced interfacial mechanics toward integration-ready perovskite modules. Full article

We report the observation of a linear electro-optic (EO) response in CsPbX₃ (X = Cl, Br, I) perovskite nanocrystal (NC) films fabricated via electrophoretic deposition (EPD). Under an alternating electric field, the EPD films exhibit clear linear EO modulation of transmitted light intensity, indicating the formation of an anisotropic medium through field-induced NC alignment. In contrast, spin-coated NC films show no measurable linear EO response, underscoring the critical role of structural anisotropy introduced by EPD. All EPD samples exhibit a decreasing EO response with increasing modulation frequency, consistent with the involvement of slow ion migration dynamics. The halide composition influences EO behavior, with Br/Cl mixed-composition films maintaining the highest EO response at elevated frequencies, and Br-based NCs showing stronger EO signals than their Cl counterparts, while Bi-doped CsPbBr₃ films exhibit quenched photoluminescence yet retain a measurable but weaker EO response, underscoring the trade-off between defect-induced nonradiative recombination and EO activity. These results highlight the potential of EPD-assembled perovskite NCs for reconfigurable EO applications by tailoring composition and microstructure. Full article

Perovskite-type CaBiO₂Cl with a unique layered Sillen X1 structure exhibits great potential as an efficient visible-light photocatalyst. In this study, CaBiO₂Cl was synthesized through calcination at 800 °C and subsequently composited with varying amounts of g-C₃N₄ to optimize photocatalytic performance. The prepared catalysts were characterized by multiple techniques to confirm their structural and compositional features. Under visible-light irradiation, the photocatalytic activities toward Rh6G degradation were systematically evaluated using UV–vis PDA and EPR analyses. To further elucidate the degradation mechanism, radical scavenger experiments were conducted to identify the reactive species generated during the photodegradation process. Kinetic analysis revealed that the reaction rate constant (k) of pure CaBiO₂Cl was 0.0525 h⁻¹, while that of pure g-C₃N₄ was 0.0423 h⁻¹. Notably, the CaBiO₂Cl/10 wt% g-C₃N₄ composite exhibited an enhanced k value of 0.0568 h⁻¹, which is 1.1 and 1.3 times higher than those of CaBiO₂Cl and g-C₃N₄, respectively. Furthermore, under ambient conditions (25 °C, 1 atm), the CO₂-to-CH₄ photocatalytic conversion efficiency of the CaBiO₂Cl/10 wt% g-C₃N₄ composite reached 0.5652 μmol g⁻¹ h⁻¹. These findings demonstrate that CaBiO₂Cl-based composite photocatalysts not only achieve superior visible-light photocatalytic activity but also exhibit excellent stability, highlighting their potential for environmental remediation and alignment with the principles of green chemistry. Full article

Lead-free perovskite variants have emerged as promising candidates due to their self-trapped exciton emission. However, in ASnX₃ systems, facile oxidation of Sn(II) to Sn(IV) yields A₂SnCl₆ vacancy-ordered derivatives. Paradoxically, despite possessing a direct bandgap, these variants exhibit diminished photoluminescence (PL). Doping engineering thus becomes essential for precise optical tailoring of A₂SnX₆ materials. Herein, through integrated first-principles calculations and spectroscopic analysis, we elucidate the luminescence mechanism in Te⁴⁺-doped (NH₄)₂SnCl₆ lead-free perovskites. Density functional theory, X-ray diffraction (XRD) patterns and X-ray photoelectron spectroscopy (XPS) confirm Te⁴⁺ substitution at Sn sites via favorable chemical potentials. Spectral interrogations, including absorption and emission profiles, reveal that the intense emission originates from the triplet STE recombination (³P₁ → ¹S₀) of Te centers. Temperature-dependent PL spectra further demonstrate strong electron–phonon coupling that induces symmetry-breaking distortions to stabilize STEs. Complementary electronic band structure and molecular orbital calculations unveil the underlying photophysical pathway. Leveraging these distinct thermal responses of PL intensity and peak position, 0.5%Te:(NH₄)₂SnCl₆ emerges as a highly promising candidate for non-contact, dual-parameter optical thermometry over an ultra-broad range (100–400 K). This work provides fundamental insights into the exciton dynamics and thermal engineering of optical properties in this material system, establishing its significant potential for advanced temperature-sensing applications. Full article

A novel, eco-friendly perovskite solar cell design is investigated using numerical simulations based on the finite-difference time-domain (FDTD) method. The proposed structure incorporates a two-dimensional (2D) photonic crystal (PhC) architecture featuring a titanium dioxide (TiO₂) cylindrical electron extraction layer. To reduce fabrication complexity and overall production costs, a hole-transport-layer-free (HTL-free) configuration is employed. Simulation results reveal a significant enhancement in photovoltaic performance compared to conventional planar structures, achieving an ultimate efficiency of 42.3%, compared to 36.6% for the traditional design—an improvement of over 16%. Electromagnetic field distributions are analyzed to elucidate the physical mechanisms behind the enhanced absorption. The improved optical performance is attributed to strong coupling between photonic modes and surface plasmon polaritons (SPPs), which enhances light–matter interaction. Furthermore, the device exhibits polarization-insensitive and angle-independent absorption characteristics, maintaining high performance for both transverse magnetic (TM) and transverse electric (TE) polarizations at incidence angles up to 60°. These findings highlight a promising pathway toward the development of cost-effective, lead-free perovskite solar cells with high efficiency and simplified fabrication processes. Full article

Inorganic lead halide perovskite semiconductor materials exhibit great potential in the optoelectronic field due to their excellent optical and electrical properties. However, lead toxicity and limited material stability hinder their commercial applications. Consequently, the pursuit of non-toxic, stable alternatives is imperative for the sustainable development of halide-perovskite semiconductors. Non-toxic germanium-based halide perovskites, as promising candidates, have attracted considerable attention. Here, we present a systematic first-principles investigation of the structural, electronic, elastic, and optical properties of cost-effective germanium-based halide perovskites NaGeX₃ (X = Cl, Br, I). Energy and phonon-spectrum calculations demonstrate that NaGeX₃ with the R3c space group exhibits the highest structural stability, rather than the commonly assumed cubic phase. Hybrid functional calculations reveal that the band gaps of R3c NaGeX₃ decrease monotonically with increasing halogen radius, that is, 4.75 eV (NaGeCl₃) → 3.76 eV (NaGeBr₃) → 2.69 eV (NaGeI₃), accompanied by a reduction in carrier effective masses. Additionally, mechanically stable R3c NaGeX₃ exhibits lower hardness and ductility than that of the cubic phase. Optical properties indicate that NaGeX₃ materials have strong absorption coefficients (>10⁶ cm⁻¹) and low loss in the photon energy range of 9–11 eV, suggesting that such cost-effective germanium-based halide perovskites can be used in various optoelectronic devices in the ultraviolet region. Full article

The rising demand for clean energy, especially hydrogen, has heightened the need for efficient storage materials. Perovskites, with their unique structures, show great promise for hydrogen storage and optical uses. To identify promising candidates for hydrogen storage materials, the mechanical, electronic, and optical properties of four ordered vacancy double perovskite structures X₂MH₆ (Ba₂BeH₆, Ba₂MgH₆, Ca₂BeH₆, and Sr₂MgH₆) were predicted using density functional theory. These materials were confirmed to be stable, and their hydrogen storage capacity, mechanical properties, electronic structures, and optical performance were thoroughly analyzed. Ca₂BeH₆ demonstrated the highest gravimetric (6.32%) and volumetric (32.29 g·H₂/L) hydrogen storage capacity, showcasing its exceptional potential. It should be noted that the hydrogen storage capacities reported here are theoretical estimates based solely on structural models, and this study does not assess the practical storage and delivery performance of these materials. Its mechanical stiffness and near-isotropic properties further enhance its practicality. Electrical studies revealed all four materials are semiconductors, all of them are direct semiconductors. Optical properties were analyzed via dielectric functions, offering key insights for designing advanced hydrogen storage and optical materials. Full article

In recent decades, photocatalysis has received huge attention as a way to address the main environmental challenges affecting planet Earth. Among these, the control of CO₂ emission and its concentration in the atmosphere, as one of the greenhouse gases causing global warming, is of primary importance. This study focuses on the hydrothermal preparation of doped Ba and Ca-based titanates as efficient photocatalytic materials for CO₂ photoreduction under solar light. The materials were characterized by SEM-EDX, XPS, FT-IR ATR, DRS, CHNS, XRD, and N₂ physisorption analyses, and tested for gas-phase methane production from the target reaction. According to the results, the visible light harvesting properties were significantly improved with C and N doping, where glucose and a bio-based chitosan acted as the C and C+N sources, respectively. In particular, C-Ba-based titanate (CBaT) indicated the highest CH₄ productivity, 2.3 µmol/g_cat, against zero activity of the corresponding bare titanate structure, BaT. The larger surface area and pore volume, as well as its narrower band gap, are suggested as the major reasons for the promising performance of CBaT. This work provides new insights for the facile fabrication of efficient photoactive perovskite materials with the aim of CO₂-to-CH₄ photoreduction under solar light. Full article