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We report an enhanced magnetoelectric (ME) effect in spin–phonon coupled single-phase La1−xSmxYFe2O6 (0 ≤ x ≤ 1). The structural, electric, magnetic, and ME properties have been investigated to establish their interplay leading to magnetoelectricity. X-ray diffraction study suggests the facilitation of the P21nm phase (double perovskite lattice arrangements) formation and improved structural order due to the substitution of Sm in the lattice. Antiferromagnetic (AFM) transition ∼700 K along with a spin-reorientation transition around room temperature (RT) and below is observed in the thermomagnetic curve. The indication of short range ordering in the magnetization data in the form of a non-Griffiths-like phase (nGP) is observed. The short range ordering could be minimized along with consequent improvement in AFM ordering, due to Sm substitution. An enhanced (∼31% with respect to x = 0) RT first-order ME coupling coefficient ∼0.59 mV cm−1 Oe−1 in x = 0.75 composition is observed. The findings reported here open the door to exercise spin-reorientation transition in the spin–phonon coupled double perovskites for spintronic device applications. [ABSTRACT FROM AUTHOR]

We report an enhanced magnetoelectric (ME) effect in spin–phonon coupled single-phase La1−xSmxYFe2O6 (0 ≤ x ≤ 1). The structural, electric, magnetic, and ME properties have been investigated to establish their interplay leading to magnetoelectricity. X-ray diffraction study suggests the facilitation of the P21nm phase (double perovskite lattice arrangements) formation and improved structural order due to the substitution of Sm in the lattice. Antiferromagnetic (AFM) transition ∼700 K along with a spin-reorientation transition around room temperature (RT) and below is observed in the thermomagnetic curve. The indication of short range ordering in the magnetization data in the form of a non-Griffiths-like phase (nGP) is observed. The short range ordering could be minimized along with consequent improvement in AFM ordering, due to Sm substitution. An enhanced (∼31% with respect to x = 0) RT first-order ME coupling coefficient ∼0.59 mV cm−1 Oe−1 in x = 0.75 composition is observed. The findings reported here open the door to exercise spin-reorientation transition in the spin–phonon coupled double perovskites for spintronic device applications. [ABSTRACT FROM AUTHOR]

High‐pressure oxides like perovskite‐type FeTiO3, CaTi2O4‐type Fe2TiO4, and ferrous‐ferric oxides that form polysomes between wüstite and CaFe2O4‐type Fe3O4 are potential carriers of Fe, Ti, and other transition metals in the mantle and may play an important role in the redox budget of the deep Earth. Here, we report the occurrence of three of these phases as the new minerals: feiite (Sr2Tl2O5‐type Fe2+2(Fe2+Ti4+)O5), liuite (FeTiO3 with a GdFeO3‐type perovskite structure), and tschaunerite (CaTi2O4‐type (Fe2+)(Fe2+Ti4+)O4), along with wangdaodeite (LiNbO3‐type FeTiO3) in a transformed ulvöspinel clast entrained in a shock melt pocket in the Shergotty Martian meteorite. We show that reaction between the shocked ulvöspinel precursor and melt occurred at pressures between 20 and 25 GPa. The high‐pressure Fe‐, Ti‐minerals lost Fe and O to the surrounding shock melt in exchange for Si, Mg, and Ca. Concentrations of Si and Mg in all of these clast phases and of Na in liuite are significant. They substantiate chemical interaction of the clast with melt during the shock event and highlight potential elemental distributions in complex Fe‐ and Ti‐rich lithologies at pressures of the deep transition zone to shallow lower mantle. [ABSTRACT FROM AUTHOR]

Tin(II) perovskite oxides are promising for lead-free ferroelectric applications because Sn(II) is isoelectronic to Pb(II) and is predicted to amplify displacements and polarization. Though typically difficult to synthesize, a metastable perovskite structure of barium zirconate titanate with Sn(II) substituted for Ba was recently reported. In the present work, a detailed structural analysis is performed on 40% Sn(II)-substituted BaZr0.5Ti0.5O3 with high-resolution synchrotron X-ray diffraction. The main diffraction peaks of the cubic perovskite persist with the incorporation of tin into the structure. Additionally, superstructure reflections are observed in the low 2θ region of the diffraction pattern at d-spacings that are multiples of the main perovskite peaks. The origin of these superstructure peaks is attributed to atomic displacements of the Sn and Zr/Ti cations. A Bayesian inference method is applied to conduct a refinement of the atomic displacements in a supercell with no symmetry constraints (i.e., P1 symmetry setting) using the superstructure diffraction reflections. In the absence of a known structure and symmetry, the Bayesian method allows for simultaneous refinement of all atomic positions without convergence to unrealistic local minima, resulting in the most probable configurations of atoms. Through the refined solution, it is found that displacements of the cations result in symmetry-breaking distortions from the parent cubic perovskite structure that can be modeled using a P1 supercell with the potential for ferroelectric polarization. [ABSTRACT FROM AUTHOR]

Chalcogenide perovskites are a family of compounds related to perovskite structures or compositions, which have witnessed rapid advances in recent years. They possess favorable properties such as high stability, low toxicity, direct band gaps, good carrier transport abilities, strong light absorption, and potential luminescent properties, making them stand out in emerging applications, such as photovoltaics, photodetectors, light-emitting devices, and photocatalysts, among others. In this review, we aim to provide a comprehensive overview of the properties, synthesis, and applications of chalcogenide perovskites. First, we first survey the reported material structures/compositions and current understanding of their structural/optical/electrical properties, mechanics, magnetics, and stabilities. Furthermore, we discuss the synthesis strategies of these materials covering various material types such as powders, pellets, thin films, nanocrystals, and single crystals, with a focus on their potential applications, including photovoltaics, photodetectors, and other devices. Finally, we outline a brief conclusion and some prospects for the further research of chalcogenide perovskites, thus promoting more studies and developments in this field. This review can provide new insights into the fundamental properties and potential applications of chalcogenide perovskites, and thereby facilitating their further studies and developments. [ABSTRACT FROM AUTHOR]

This study investigates the potential of Cesium−formamidinium-based (CsyFA1−yPb(IxBr1−x)3) perovskite materials as promising candidates for efficient and stable perovskite solar cells (PSCs), that can be tailored for indoor applications. These materials offer the unique advantage of simultaneously stabilizing photoactive compositional phase transitions and enhancing thermal stability, making them well-suited for indoor environments. The optical band gaps of Cesium−formamidinium, ranging from 1.5 to 1.8 eV, can be engineered to align with the spectrum of light sources commonly used indoors. Therefore, this study directs into the design and simulation of Cesium-Formamidinium-Based PSCs, with a specific emphasis on optimizing their performance under indoor LED illumination. Parameter manipulation related to the Hole Transport Layer (HTL) and Electron Transport Layer (ETL) is utilized to establish optimal band alignment in order to reduce recombination losses and boost power conversion efficiency. A co-design approach between the ETL and HTL is introduced, enabling precise engineering of interfaces, and optimizing charge transport and collection efficiency. This research presents an optimal design with a conduction band minimum (VBM) energy level of 4.05 eV for the ETL and a valence band maximum (VBM) energy level of 5.15 eV for the HTL, resulting in a power conversion efficiency (PCE) of 25.00%, and an open-circuit voltage (Voc) of 0.939 V. [ABSTRACT FROM AUTHOR]

This study prepared ultralow electron-loss perovskites with spinel-like structures via a solid-state reaction. The (Mg0.95Co0.05)2(Ti0.95Sn0.05)O4 (MCTS) ceramic exhibited approximate values for ultrahigh quality factor, permittivity, and negative temperature coefficient (τf) of 310,000 GHz, 14.25, and −48.1 ppm/oC, respectively. To bring the τf closer to zero, a trace amount of (Ca0.95Sr0.05)(Ti0.97Sn0.03)O3 (CSTS) perovskite was added to MCTS during ceramic manufacturing. CSTS exhibited a permittivity of 92 and a large positive τf value of 810 ppm/°C. A 0.92MCTS–0.08CSTS hybrid ceramic sintered at 1325°C achieved remarkable microwave dielectric properties of εr ~18.42, Q×f ~ 237,000 GHz and τf ~3.72 ppm/°C. This mixed ceramic has significant potential for applications in manufacturing microwave devices. [ABSTRACT FROM AUTHOR]

The switch to sustainable power generation sources has gained substantial spotlight due to the essential need to decrease fossil fuels dependence, and alleviate climate change issues. This research aims to explore the first principle calculations for geometrical structure, enthalpy of formation, electronic structure behavior, optical spectra, and photocatalytic performance of the clean new Iodine-based triple perovskite compounds A3B2I9 (A = Rb or Cs, and B = Sb or Bi) using FP-LAPW method based on the density functional theory implemented in Wien2K software. The outcomes prove that these triple perovskite compounds can be formed spontaneously under standard conditions, because they are thermodynamically stable. Moreover, the electronic band structure shows an indirect semiconductor behavior of all studied compounds. Further, the optical spectra highlights that all studied compounds have high visible light absorption due to their suitable forbidden band values [1.8 eV–2.369 eV] which facilitate efficient electron–hole pairs generation maximizing the conversion of light into electrical energy. In addition, all studied compounds are satisfied the limits necessary to split water and then to produce hydrogen. Consequently, these compounds are most likely to be used as Lead-free perovskites in various optoelectronic applications, especially solar cells and hydrogen production from water splitting. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have garnered remarkable attention for their efficiency and tunable optoelectronic properties. However, their instability to moisture and heat poses challenges. Traditional trial‐and‐error approaches for finding stable halide perovskites are inefficient due to the vast compositional possibilities within ABX3 perovskite structure. This study uses machine learning (ML) to predict bandgaps and photovoltaic parameters of PSCs, using a dataset of 447 data points containing chemical composition, bandgaps, and photovoltaic parameters. Various ML models including support vector regressor, random forest, gradient boost regressor, XGBoost, extratree Regressor, and AdaBoost Regressor have been used herein. Positional average elemental property (PAEP) approach is introduced to featurize the data. As ABX3 perovskite involves distinct A, B, and X sites, the proposed PAEP model captures site‐specific effects, enhancing model accuracy. The best model exhibits impressive r‐values of 0.98 for bandgap prediction and 0.86 for power conversion efficiency of PSCs. Elemental properties of B and X sites, such as ionization energy, electron affinity, and electronegativity, are found to be crucial features in the analysis by Shapley additive explanation. This study underscores the potential of ML in designing novel, stable, and efficient PSCs, offering a more efficient alternative to conventional trial‐and‐error methods. [ABSTRACT FROM AUTHOR]

Perovskite oxides, with their diverse properties and versatile structures, have emerged as promising materials for electrochemical energy storage devices. The X‐ray diffraction patterns of both BaLaMnFeO6 (BLMFO), and its reduced graphene oxide (rGO) composite, synthesized through solvothermal process, revealed the formation of rhombohedral structure with space group R‐3C (no. 167). The estimated lattice parameter are a = 5.59 Å, b = 5.59 Å and c = 13.60 Å. As per the Brunauer–Emmett–Teller (BET) analysis, BLMFO/rGO composite (≈32.12 m2 g−1) exhibited a higher specific surface area than pristine BLMFO (≈11.85 m2 g−1), which has been attributed to the enhanced porosity resulted due to addition of rGO. The specific capacitance of pristine BLMFO and composite BLMFO/rGO is found to be 170.7 and 330.2 Fg−1, respectively, at the current density 1 Ag−1. The present investigation on the solvothermal synthesis and electrochemical analysis of BLMFO perovskite and its rGO composite, demonstrates potential for energy storage application. [ABSTRACT FROM AUTHOR]

In this work, theoretical investigations were performed for the structural, elastic, optoelectronic, thermodynamic, and thermoelectric characteristics of barium ceroplatinate Ba2CePtO6 double perovskite oxide. The direct band gaps 1.518 eV and 1.385 are calculated with TB-mBJ potential, and PBE-GGA approximation. The findings of elastic constants C11, C12 and C44, ensure the mechanical stability, ductile nature, anisotropic, Debye temperature, and ionic bonding. In visible and ultraviolet spectrums, Ba2CePtO6 exhibits a high absorption coefficient (> 105 cm−1), low optical reflectivity, low electron energy loss and excellent refractive index. Finally, the thermoelectric properties are computed using BoltzTraP code. At room temperature the figure of merit has been reported as 0.84 and 0.998. Therefore, the reported results are likely to serve as an inspiration for the forthcoming experimental and theoretical investigations. [ABSTRACT FROM AUTHOR]

Lead Halide Perovskites (LHPs) have garnered great attention in recent times due to their astonishing properties that range from direct tunable bandgaps, strong light absorption, defect resistance and the easily accessible synthesis of high‐quality crystals and films. These materials find application in multitudinous fields including photovoltaics, optoelectronics, lasers, catalysis and in the emerging field of spintronics. Though they show exceptional optoelectronic properties with enhanced applications, the instability of LHPs act as a main downside when it comes to real world applications. Integrating complementary materials to LHPs that form composites with better stability along with improved performance have started to gain traction. These composites and heterostructures incorporating functional materials with LHPs have made the utilization of perovskites in everyday life more feasible. The existing synthetic strategies for heterostructure and composites heavily draw from the techniques used for halide perovskite synthesis. These methods often under‐utilize the potential of exploring the synergy of materials interaction. This review explores the synthesis methods followed to produce these hybrid materials focusing on the improvements required in terms of fundamental studies and their applications. [ABSTRACT FROM AUTHOR]

In this communication, we report a typical structural, optical and electrical analysis of thin films of hole transport material (HTM) based on aromatic phenyl benzidine derivative (N,N ′ -Di-1-naphthyl-N,N ′ -diphenylbenzidine) deposited by thermal evaporation technique onto the glass substrate. The effect of substrate temperature on the physical and electronic properties of these organic thin films for perovskite solar cells (PSCs) applications has been investigated. The films have been characterized by FTIR, XRD, SEM, UV–Vis spectroscopy and photoluminescence spectroscopy. Electrical conductivity and activation energies of films have also been calculated. From FTIR data of fabricated films and powder, it was found that the compound does not decompose during the thermal evaporation process as observed vibrational frequencies of films and the powder are the same. From the results, it has been determined that the substrate temperature has a huge impact on the physical structure and has also influenced the optical, electrical properties of the films. As observed from the studies it appears that these amorphous films with bandgap near to 3 eV and suitable conductivity have potential for photovoltaics layer devices. From this study, it can be concluded that N,N ′ -Di-1-naphthyl-N,N ′ -diphenylbenzidine can be used as an active hole transport layer in PSCs. [ABSTRACT FROM AUTHOR]

Halide base perovskite LiCdX3 (X = F, Cl) is tested by CASTEP (Cambridge Serial Total Energy Package) based on density function theory (DFT). The presented discussion is to explore the structural, electronic, and optical properties of LiCdX3 (X = F, Cl). The calculated values of the lattice parameter are found to be 3.8 Å and 5.27 Å of LiCdF3 and LiCdCl3 respectively. The ideal structure of LiCdX3 (X = F, Cl) is cubic and dynamically stable. Electronic properties show that materials are semiconductors. The results from band structure are further evaluated by the total and partial density of states. The partial and total density of states confirms the degree of localization of electrons. In optical properties, the highest absorption coefficient is observed in LiCdCl3. The material is half metallic and has a narrow indirect band gap which may be used in photovoltaic applications. [ABSTRACT FROM AUTHOR]

Over the past few decades, organic–inorganic halide perovskites (OIHPs) as novel photocatalyst materials have attracted intensive attention for an impressive variety of photocatalytic applications due to their excellent photophysical (chemical) properties. Regarding practical application and future commercialization, the air–water stability and photocatalytic performance of OIHPs need to be further improved. Accordingly, studying modification strategies and interfacial interaction mechanisms is crucial. In this review, the current progress in the development and photocatalytic fundamentals of OIHPs is summarized. Furthermore, the structural modification strategies of OIHPs, including dimensionality control, heterojunction design, encapsulation techniques, and so on for the enhancement of charge‐carrier transfer and the enlargement of long‐term stability, are elucidated. Subsequently, the interfacial mechanisms and charge‐carrier dynamics of OIHPs during the photocatalytic process are systematically specified and classified via diverse photophysical and electrochemical characterization methods, such as time‐resolved photoluminescence measurements, ultrafast transient absorption spectroscopy, electrochemical impedance spectroscopy measurements, transient photocurrent densities, and so forth. Eventually, various photocatalytic applications of OIHPs, including hydrogen evolution, CO2 reduction, pollutant degradation, and photocatalytic conversion of organic matter. [ABSTRACT FROM AUTHOR]

This work mainly focuses on synthesizing and evaluating the efficiency of methylammonium lead halide‐based perovskite (MAPbX3; X=Cl, Br, I) solar cells. We used the colloidal Hot‐injection method (HIM) to synthesize MAPbX3 (X=Cl, Br, I) perovskites using the specific precursors and organic solvents under ambient conditions. We studied the structural, morphological and optical properties of MAPbX3 perovskites using XRD, FESEM, TEM, UV‐Vis, PL and TRPL (time‐resolved photoluminescence) characterization techniques. The particle size and morphology of these perovskites vary with respect to the halide variation. The MAPbI3 perovskite possesses a low band gap and low carrier lifetime but delivers the highest PCE among other halide perovskite samples, making it a promising candidate for solar cell technology. To further enrich the investigations, the conversion efficiency of the MAPbX3 perovskites has been evaluated through extensive device simulations. Here, the optical constants, band gap energy and carrier lifetime of MAPbX3 were used for simulating three different perovskite solar cells, namely I, Cl or Br halide‐based perovskite solar cells. MAPbI3, MAPbBr3 and MAPbCl3 absorber layer‐based devices showed ~13.7 %, 6.9 % and 5.0 % conversion efficiency. The correlation between the experimental and SCAPS simulation data for HIM‐synthesized MAPBX3‐based perovskites has been reported for the first time. [ABSTRACT FROM AUTHOR]

The emerging solution‐based solar cells and photodetectors have gained worldwide research interest over the past decades. Hole transport materials (HTMs) have greatly advanced the progress of these solution‐based electronics. Nevertheless, developing low‐cost and efficient HTMs is far from satisfactory. In this contribution, poly(3‐pentylthiophene) (P3PT) is introduced as a facile, low‐cost, and versatile dopant‐free polymer HTM for both quantum dot (QD) and perovskite electronic devices. Compared to the broadly used poly(3‐hexylthiophene), P3PT presents the reduced molecular aggregation and preferential face‐on orientation, which can markedly enhance the hole‐carrier transport in optoelectronic devices. Accordingly, P3PT can deliver the substantial improvement of photovoltaic performance from ∼8.6% to ∼9.5% for QD/polythiophene solar cells and from ∼16% to ∼18.8% for perovskite/polythiophene solar cells, which are both among the topmost values in the corresponding fields. Furthermore, P3PT HTMs can also significantly enhance the photodetection performance of QD and perovskite photodetectors by a factor of ∼3, indicating its great application potential in a variety of emerging optoelectronics. [ABSTRACT FROM AUTHOR]

In this study, the perovskite‐type oxide LaFeO3 is treated by electroless Ni deposition with different reaction time and the electrochemical properties of the resulting material are investigated as the anode for MH‐Ni batteries. XRD, SEM, and TEM measurements reveal a uniform deposition of crystalline nickel on the oxide surface and a clear increase in the amount of Ni coating with the deposition time. The electrochemical analysis shows that the electroless deposition can significantly improve the maximum discharge capacity of the battery. Furthermore, the coated electrodes exhibit excellent activation performance and superior cyclic stability. With the increase in the reaction temperature, improvements in the discharge ability, exchange current density, and diffusing coefficient of hydrogen are also observed. [ABSTRACT FROM AUTHOR]

The strain engineering effects induced by different means, e.g., the substrate lattice mismatch and/or chemical doping, on the functional properties of perovskite thin films have triggered interest in the use of these materials in different applications such as energy storage/generation or photonics. The effects of the film's thickness and strain state of the structure for the lead-free perovskite ferrite-based materials (BiFeO3-BFO; Y-doped BiFeO3-BYFO; LaFeO3-LFO) on their functional properties are highlighted here. As was previously demonstrated, the dielectric properties of BFO epitaxial thin films are strongly affected by the film thickness and by the epitaxial strain induced by the lattice mismatch between substrate and film. Doping the BiFeO3 ferroelectric perovskite with rare-earth elements or inducing a high level of structural deformation into the crystalline structure of LaFeO3 thin films have allowed the tuning of functional properties of these materials, such as dielectric, optical or photocatalytic ones. These changes are presented in relation to the appearance of complex ensembles of nanoscale phase/nanodomains within the epitaxial films due to strain engineering. However, it is a challenge to maintain the same level of epitaxial strain present in ultrathin films (<10 nm) and to preserve or tune the positive effects in films of thicknesses usually higher than 30 nm. [ABSTRACT FROM AUTHOR]

Perovskite oxides with unique crystal structures and high defect tolerance are promising as atomic surface passivation layers for photoelectrodes for efficient and stable water splitting. However, controllably depositing and crystalizing perovskite-type metal oxides at the atomic level remains challenging, as they usually crystalize at higher temperatures than regular metal oxides. Here, we report a mild solution chemistry approach for the quasiepitaxial growth of an atomic CaTiO3 perovskite layer on rutile TiO2 nanorod arrays. The high-temperature crystallization of CaTiO3 perovskite is overcome by a sequential hydrothermal conversion of the atomic amorphous TiOx layer to CaTiO3 perovskite. The atomic quasi-epitaxial CaTiO3 layer passivated TiO2 nanorod arrays exhibit more efficient interface charge transfer and high photoelectrochemical performance for water splitting. Such a mild solution-based approach for the quasi-epitaxial growth of atomic metal oxide perovskite layers could be a promising strategy for both fabricating atomic perovskite layers and improving their photoelectrochemical properties. [ABSTRACT FROM AUTHOR]

Air‐stable p‐type SnF2:Cs2SnI6 with a bandgap of 1.6 eV has been demonstrated as a promising material for Pb‐free halide perovskite solar cells. Crystalline Cs2SnI6 phase is obtained with CsI, SnI2, and SnF2 salts in gamma‐butyrolactone solvent, but not with dimethyl sulfoxide and N,N‐dimethylformamide solvents. Cs2SnI6 is found to be stable for at least 1000 h at 100 °C when dark annealed in nitrogen atmosphere. In this study, Cs2SnI6 has been used in a superstrate n–i–p planar device structure enabled by a spin‐coated absorber thickness of ≈2 μm on a chemical bath deposited Zn(O,S) electron transport layer. The best device power conversion efficiency reported here is 5.18% with VOC of 0.81 V, 9.28 mA cm−2JSC, and 68% fill factor. The dark saturation current and diode ideality factor are estimated as 1.5 × 10−3 mA cm−2 and 2.18, respectively. The devices exhibit a high VOC deficit and low short‐circuit current density due to high bulk and interface recombination. Device efficiency can be expected to increase with improvement in material and interface quality, charge transport, and device engineering. [ABSTRACT FROM AUTHOR]

All-inorganic and organic–inorganic hybrid perovskite solar cells (PSCs) have taken a quantum leap owing to their high performance and low-cost solution processability. Their efficiency has been dramatically increased up to ∼26%, matching the conventional inorganic photovoltaics like monocrystalline Si (26.1%), polycrystalline Si (21.6%), CdTe (22.1%), and CIGS (22.3%). Such outstanding performance has been achieved due to their excellent optoelectronic properties, such as a direct bandgap in the visible region, a very high absorption coefficient, a long charge-carrier diffusion length, and ambipolar carrier transport characteristics. FAPbI3 (FA = formamidinium) and CsPbI3 perovskites among the pool of perovskites are recommended for solar cell applications because they meet all the requirements for photovoltaic applications. However, the fundamental problem of these perovskites is that their photoactive black phase is highly unstable under ambient conditions due to small and large sizes of Cs+ and FA+ ions, respectively. The instability of the black phase of these perovskites hinders their applications in photovoltaic devices as a high-quality light absorber layer. Several approaches have been employed to prevent the formation of the photo-inactive yellow phase or to enhance the stability of the black phase of perovskites, such as dimensional and compositional engineering, the addition of external additives, and dimensional engineering. This perspective summarizes the various methods for stabilizing the black phase of CsPbI3 and FAPbI3 perovskites at room temperature as well as their application in photovoltaic devices. [ABSTRACT FROM AUTHOR]

The flexible type of displays, which can alter their shape freely (e.g., bendable or foldable displays) according to situational demands, is under an intense spotlight due to applications in human‐friendly mobile electronics. Among various types of light‐emitting diodes (LEDs), meanwhile, perovskite‐based LEDs (PeLEDs) have garnered particular attention in recent years as next‐generation optoelectronic devices due to their exceptional optical characteristics, such as high efficiency (up to theoretical limits), high color purity, wide color gamut over the entire visible range, and ultrathin form factor. By integrating perovskite materials on an ultrathin flexible substrate with a proper encapsulation layer, the flexible PeLEDs, which can conform to various curved surfaces and be stably operated in an ambient condition, have been developed. Here, recent advances of the flexible PeLEDs are reviewed. First, light‐emitting materials and device structures for the PeLEDs are introduced. Then, research progress on the flexible PeLEDs, either with and without the encapsulation layer are summarized. Next, some representative application examples of the flexible PeLEDs are briefly discussed. Finally, this review includes a brief discussion on future prospects. [ABSTRACT FROM AUTHOR]

This study is on the enhancement of the efficiency of wide bandgap (FA0.8Cs0.2PbI1.8Br1.2) perovskite solar cells (PSCs) used as the top layer of the perovskite/perovskite tandem solar cell. Poly[bis(4‐phenyl) (2,4,6‐trimethylphenyl) amine] (PTAA) and the monomolecular layer called SAM layer are effective hole collection layers for APbI3 PSCs. However, these hole transport layers (HTL) do not give high efficiencies for the wide bandgap FA0.8Cs0.2PbI1.8Br1.2 PSCs. It is found that the surface‐modified PTAA by monomolecular layer (MNL) improves the efficiency of PSCs. The improved efficiency is explained by the improved FA0.8Cs0.2PbI1.8Br1.2 film quality, decreased film distortion (low lattice disordering) and low density of the charge recombination site, and improves carrier collection by the surface modified PTAA layer. In addition, the relationship between the length of the alkyl group linking the anchor group and the carbazole group is also discussed. Finally, the wide bandgap lead PSCs (Eg = 1.77 eV) fabricated on the PTAA/monomolecular bilayer give a higher power conversion efficiency of 16.57%. Meanwhile, all‐perovskite tandem solar cells with over 25% efficiency are reported by using the PTAA/monomolecular substrate. [ABSTRACT FROM AUTHOR]

Crystalline materials have governed the development of hybrid organic‐inorganic perovskites (HOIPs), giving rise to a variety of fascinating applications such as solar cells and optoelectronic devices. With increasing interest in non‐crystalline systems, the glassy state of HOIPs has recently been identified. Here, the basic building blocks of crystalline HOIPs appear to be retained, though their glasses lack long‐range periodic order. The emerging family of glasses formed from HOIPs exhibits diverse properties, complementary to their crystalline state. This mini review describes the chemical diversity of both three‐dimensional and two‐dimensional crystalline HOIPs and demonstrates how glasses are produced from these materials. Specifically, current achievements in melt‐quenched glasses formed from HOIPs are highlighted. We conclude with our perspective on the future of this new family of materials. [ABSTRACT FROM AUTHOR]

Nitride perovskite LaWN3 has been predicted to be a promising ferroelectric material with unique properties for diverse applications. However, due to the challenging sample preparation at ambient pressure, the crystal structure of this nitride remains unsolved, which results in many ambiguities in its properties. Here, the authors report a comprehensive study of LaWN3 based on high‐quality samples synthesized by a high‐pressure method, leading to a definitive resolution of its crystal structure involving nitrogen deficiency. Combined with theoretical calculations, these results show that LaWN3 adopts an orthorhombic Pna21 structure with a polar symmetry, possessing a unique atomic polarization along the c‐axis. The associated atomic polar distortions in LaWN3 are driven by covalent hybridization of W: 5d and N: 2p orbitals, opening a direct bandgap that explains its semiconducting behaviors. The structural stability and electronic properties of this nitride are also revealed to be closely associated with its nitrogen deficiency. The success in unraveling the structural and electronic ambiguities of LaWN3 would provide important insights into the structures and properties of the family of nitride perovskites. [ABSTRACT FROM AUTHOR]

Caesium-based mixed halide perovskite single crystals, CsPbBr3-xIx, are shown to be good candidates for many optoelectronic applications under ambient conditions. The partial substitution of iodine into the bromine sites of CsPbBr3 single crystal makes attractive effects in optical and structural properties as well as their thermal and phase stability. Herein, the Inverse Temperature Crystallization (ITC) method has been utilised to grow high-quality, large, and single-phase single crystals of CsPbBr2.4I0.6 perovskites. The iodine doping is found to result in improved purity, thermal, phase, and atmospheric stability of the single crystal and helped to tune the band gap. Further, there is a conspicuous decrease in the defect density with iodine doping. Thus the present study establishes iodine doping as a facile route to grow CsPbBr3 single crystals with overall stability and improved defect density with a broad absorption spectrum, that point toward extended optoelectronic and photovoltaic applications. [ABSTRACT FROM AUTHOR]

Lead-free halide double perovskites are stable and versatile materials for a wide range of applications, particularly for lighting, thanks to their very efficient emission of warm white light. Element substitution in halide double perovskite is recognized as a powerful method for tuning the emission wavelength and improve the efficiency. This review provides an overview on composition and recent progress in halide double perovskite with main focus on the synthesis and emission properties of chloride-based compounds. [ABSTRACT FROM AUTHOR]

The exact control of material properties essential for solar applications has been made possible because of perovskites' compositional engineering. However, tackling efficiency, stability, and toxicity at the same time is still a difficulty. Mixed lead-free and inorganic perovskites have lately shown promise in addressing these problems, but their composition space is vast, making it challenging to find good candidates even with high-throughput approaches. We investigated two groups of halide perovskite compound data with the ABX3 formula to investigate the formation energy data for 81 compounds. The structural stability was analyzed over 63 compounds. For these perovskites, we used new library data extracted from a calculation using generalized-gradient approximation within the Perdew–Burke–Ernzerhof (PBE) functional established on density functional theory. As a second step, we built machine learning models, based on a kernel-based naive Bayes algorithm that anticipate a variety of target characteristics, including the mixing enthalpy, different octahedral distortions, and band gap calculations. In addition to laying the groundwork for observing new perovskites that go beyond currently available technical uses, this work creates a framework for finding and optimizing perovskites in a photovoltaic application. [ABSTRACT FROM AUTHOR]

The increase in cost-effective materials for harvesting solar energy is essential for the development of renewable energy technologies. Photovoltaics and photocatalysts are been actively researched in the field of harvesting solar photons. In this communication, we explore stable Ru-doped Ba 2 HoSbO 6 (BHSR) complex perovskites with promising photocatalytic properties and a bandgap that is tunable in the UV–Vis region. The band gap shows a non-linear decrease with increased Ru doping, which follows an asymmetrically-weighted Vegard's law. UV–Visible absorption measurements and density functional theory (DFT) based simulations reveal a transition in magnitude (energy) as well as nature of the band structure (direct-to-indirect) upon Ru substitution; an observation which is unique and can influence future band structure engineering in perovskite oxides. This tailored band structure engineering plays an important role in the carrier recombination process aptly captured through photoluminescence (PL) spectroscopy. The photocatalytic activity of BHSR is demonstrated through a time varying photo-degradation of rhodamine B (Rh–B)-particulate BHSR solution. The catalytic activity is seen to improve with increased Ru doping which can be attributed to the reduction in the electron localization (electrical conductivity), increased dielectric screening, decrease in band gap and carrier recombination (electronic structure). [ABSTRACT FROM AUTHOR]

The internal friction and creep deformation behavior of La0.8Ca0.2CoO3 and pure LaCoO3 mixed ionic electronic conducting perovskite ceramics have been studied by Dynamic Mechanical Analysis and uniaxial compression under constant applied load, respectively. It was found that both the internal friction and creep strain were almost an order of magnitude higher for Ca2+ doped LaCoO3 as compared to pure undoped LaCoO3. The difference in Ca2+ doped LaCoO3 behavior was attributed to the much higher concentration of point defects (e.g., oxygen vacancies) in the structure and their interaction with other mobile defects, such as ferroelastic domain/twin walls, stacking faults, dislocations, etc. Such interactions of numerous point defects with domain walls produce energetic barriers and slow down the movement of ferroelastic domain walls under applied stress. At the same time, the defects' interactions increase the internal friction resulting in a much higher creep strain of La0.8Ca0.2CoO3 as compared to pure LaCoO3, as the creep strain is determined by the distance between the domain wall and its equilibrium position at the onset of the creep process. Therefore, the high friction will result in the larger distance the wall has to move to reach the equilibrium which in turn results in higher creep strain. The expansion of LaCoO3 under constant applied compressive stress, named here as negative creep, was also discovered to occur during room temperature creep experiments. [ABSTRACT FROM AUTHOR]

The power conversion efficiency of organic–inorganic halide perovskite solar cells is exceeding 22%. However, their potential for low cost and facile fabrication process needs to overcome barriers related to environmental stability and compatibility. Herein, using first-principles calculations, we studied the structural and electronic properties of air molecules (H2O, O2, N2, and CO2) in MAPbI3 and FAPbI3. Both formation energy and electronic band structures show large differences for H2O and O2 in these perovskites. In addition, the stability of inorganic perovskite, CsPbI3, was investigated and compared with the aforementioned organic ones. Based on the degradation mechanisms revealed by crosswise comparative analysis here, possible routes can be developed to stabilize the hybrid perovskite solar cells and thus accelerate their commercial applications. [ABSTRACT FROM AUTHOR]

A multi-step ion-exchange methodology was developed for the fabrication of Cu(LaTa2O7)2 lamellar architectures capable of wastewater depollution. The (001) diffraction line of RbLaTa2O7 depended on the guest species hosted by the starting material. SEM and TEM images confirmed the well-preserved lamellar structure for all intercalated layered perovskites. The UV–Vis, XPS, and photocurrent spectroscopies proved that Cu intercalation induces a red-shift band gap compared to the perovskite host. Moreover, the UV–Vis spectroscopy elucidated the copper ions environment in the Cu-modified layered perovskites. H2-TPR results confirmed that Cu species located on the surface are reduced at a lower temperature while those from the interlayer occur at higher temperature ranges. The photocatalytic degradation of phenol under simulated solar irradiation was used as a model reaction to assess the performances of the studied catalysts. Increased photocatalytic activity was observed for Cu-modified layered perovskites compared to RbLaTa2O7 pristine. This behavior resulted from the efficient separation of photogenerated charge carriers and light absorption induced by copper spacer insertion. [ABSTRACT FROM AUTHOR]

2D Ruddlesden–Popper halide perovskites have attracted considerable attention due to their desirable optoelectronic properties, high chemical and structural tunability, and improved environmental stability. However, the understanding of their structure–properties relationships is still limited. In particular, the energy level positions and band alignments at interfaces involving these materials, which are important features to control in the context of any applications, are still under debate. Here, the electronic structure of high‐purity films of BA2MAn−1PbnI3n+1 for n = 1–5 (where BA stands for butylammonium and MA for methylammonium) is investigated, using optical absorption, ultraviolet, and inverse photoemission spectroscopies, and density functional theory calculations. This study determines the ionization energy and electron affinity of each compound and demonstrates a type‐I band alignment for the BA2MAn−1PbnI3n+1 series. This study further describes the evolution of the exciton binding energy as a function of the thickness of the inorganic layers. [ABSTRACT FROM AUTHOR]

In this paper, the synthesis and characterization (structural, dielectric, electrical and optical) of a double perovskite, BaSrZrMnO6 (BSZMO), by a conventional solid-state reaction route are reported. The sample has an orthorhombic crystal symmetry with an average crystallite size of 40.7 nm and a micro-lattice strain of 0.226%. A microstructural and compositional analysis was presented by using a scanning electron microscope (SEM) and energy dispersive x-ray analysis (EDX), respectively. Grains are well-grown and distributed uniformly through well-defined grain boundaries on the sample surface to enhance physical properties. EDX analysis confirms the presence of all constituent elements and is well-supported by the Raman study. The analysis of the UV–Visible spectrum reveals an energy bandgap of 2.1 eV, suitable for photovoltaic applications. The study of dielectric properties as a function of temperature and frequency reveals a Maxwell–Wagner type of dispersion and explores possible applications in energy storage devices. The discussion on the impedance spectroscopy supports the negative temperature coefficient of resistance (NTCR) character whereas the modulus study suggests a non-Debye type of relaxation in the sample. The study of AC conductivity confirms a thermally activated relaxation process. Both Nyquist and Cole–Cole plots support the semiconducting nature of the sample. The study of resistance versus temperature (R ∼ T) supports NTC thermistor character for temperature sensor applications. The analysis of the P-E loop reveals the possibility of the ferroelectrics' character. [ABSTRACT FROM AUTHOR]

We report the structures of three new materials in the MDABCO-based perovskite family. Analysis of the Goldschmidt tolerance factor and octahedral factor enable us to propose compositional limits for pseudo-cubic perovskite phase formation and suggest directions for further materials discovery in this family of new ferroelectrics. [ABSTRACT FROM AUTHOR]

A high-pressure-synthesized double perovskite Sr2YOsO6 was investigated by synchrotron X-ray diffraction and measurements of its magnetic susceptibility, specific heat capacity, complex impedance, and complex dielectric constant. It crystallized into a monoclinic double perovskite structure (P21/n) with complete ordering of the Y and Os atoms. Its magnetic behaviors, including the antiferromagnetic transition temperature (~52 K), Curie-Weiss effective moment [3.48(5) μB/Os], and Weiss temperature [-350.1(7) K], were close to the respective values of Sr2YOsO6 previously synthesized without an applied pressure of 6 GPa. Transport property measurements revealed that the lower limit of the activation energy was 192(1) meV and the charge gap remained open regardless of the presence of magnetic order, conflicting with the electron delocalization predicted by theoretical calculations. Further consideration, including theoretical and experimental investigations of the roles of spin-orbit coupling and U of the 5d electrons of Os 5d-t2g³, may assist in understanding the general magnetic and insulating behaviors of quasi-half-filled 5d-t2g 3oxides in the perovskite category toward the use of 5d double perovskite for magnetic applications. [ABSTRACT FROM AUTHOR]

A high-pressure-synthesized double perovskite Sr2YOsO6 was investigated by synchrotron X-ray diffraction and measurements of its magnetic susceptibility, specific heat capacity, complex impedance, and complex dielectric constant. It crystallized into a monoclinic double perovskite structure (P21/n) with complete ordering of the Y and Os atoms. Its magnetic behaviors, including the antiferromagnetic transition temperature (~52 K), Curie-Weiss effective moment [3.48(5) μB/Os], and Weiss temperature [-350.1(7) K], were close to the respective values of Sr2YOsO6 previously synthesized without an applied pressure of 6 GPa. Transport property measurements revealed that the lower limit of the activation energy was 192(1) meV and the charge gap remained open regardless of the presence of magnetic order, conflicting with the electron delocalization predicted by theoretical calculations. Further consideration, including theoretical and experimental investigations of the roles of spin-orbit coupling and U of the 5d electrons of Os 5d-t2g³, may assist in understanding the general magnetic and insulating behaviors of quasi-half-filled 5d-t2g 3oxides in the perovskite category toward the use of 5d double perovskite for magnetic applications. [ABSTRACT FROM AUTHOR]

A series of unsynthesized perovskite-type oxyhydrides ATiO2H(A= Li, Na, K, Rb, Cs) are investigated by the density functional calculations. These oxyhydrides are stable in the sense of the formation energies for some possible synthesis reactions. They are crystallized into quite similar crystal structures with the long c-axis, and the corner-sharing TiO4H2 octahedra of the ideal perovskite-type structure are deformed into the 5-fold coordinated titanium atoms with the OH plane and the apical oxygen atoms. All of these oxyhydrides exhibit two-dimensional electronic states at the valence band maximum characterized by the in-plane oxygen 2p and the hydrogen 1s orbitals. While the c-axis becomes short as the ionic radius of the A atom becomes small and the two-dimensional characteristics are weakened, the electronic state at the valence band maximum is still characterized as the O--H in-plane state. Additionally, the Born effective charge tensors, spontaneous electric polarizations, dielectric tensors, and piezoelectric tensors are evaluated. It is found that the spontaneous electric polarizations of these oxyhydrides are much larger than that of tetragonal BaTiO3. [ABSTRACT FROM AUTHOR]

This article describes the structure and the electronic properties of a series of layered perovskites of a general formula (A+)2(SnX4)-2 where X = I, Br and A+ is an organic cation, either formamidinium, 1-methylimidazolium, or phenylethylammonium. For each system, two conformations are considered, with eclipsed or staggered stacking of the adjacent inorganic layers. Geometry optimizations are performed at the density functional theory level with generalized gradient approximation (GGA) functional and semiempirical correction for dispersion energies; band profiles and bandgaps are computed including both spin orbit coupling (SOC) and correlation (GW) effects through an additive scheme. The theoretical procedures are validated by reproducing the experimental data of a well known 3D tin iodide perovskite. The results, combined with the calculations previously reported on PbI4 analogues, allow us to discuss the effect of cation, metal, and halide substitution in these systems and in particular to explore the possibility of changing the electronic bandgap as required by different applications. The balance of SOC and GW effects depends on the chemical nature of the studied perovskites and strongly influences the value of the simulated bandgap. [ABSTRACT FROM AUTHOR]

Applications of metal halide perovskite have been rapidly developing in recent years. However, very little research focusing on basic growth kinetics of perovskite films can be found in the literature. This paper discusses a hybrid physical-chemical deposition process of planar perovskite films. A 2-D ANSYS Fluent simulation is presented to calculate the heat and mass transfer during the deposition process. An optimized mass flow configuration with a flow resistance imposed by a porous screen is shown to give a uniform distribution of the methylammonium iodide vapor precursor and an even surface deposition rate of perovskite films. Both steady and transient calculations indicate that increasing operating temperature or vessel pressure within certain limits can boost the surface deposition rate of perovskite. Limitations on working pressure are presented for preventing reverse flow into the chamber and associated deterioration of deposition uniformity of the perovskite films. [ABSTRACT FROM AUTHOR]

Applications of metal halide perovskite have been rapidly developing in recent years. However, very little research focusing on basic growth kinetics of perovskite films can be found in the literature. This paper discusses a hybrid physical-chemical deposition process of planar perovskite films. A 2-D ANSYS Fluent simulation is presented to calculate the heat and mass transfer during the deposition process. An optimized mass flow configuration with a flow resistance imposed by a porous screen is shown to give a uniform distribution of the methylammonium iodide vapor precursor and an even surface deposition rate of perovskite films. Both steady and transient calculations indicate that increasing operating temperature or vessel pressure within certain limits can boost the surface deposition rate of perovskite. Limitations on working pressure are presented for preventing reverse flow into the chamber and associated deterioration of deposition uniformity of the perovskite films. [ABSTRACT FROM AUTHOR]

Polarized‐light detection in the deep ultraviolet solar‐blind region is indispensable for optoelectronic applications. 2D hybrid perovskite ferroelectrics with inherent anisotropy and bulk photovoltaic effect (BPVE) have become a robust candidate in this portfolio. We here report a wide band‐gap 2D perovskite ferroelectric, (isobutylammonium)2(methylamium)Pb2Cl7 (1), in which the BPVE behaves as self‐driving source for solar‐blind ultraviolet polarized‐light detection. It exhibits a large dichroism ratio (≈15.7) and superior BPVE‐directed photocurrent (≈3.6 μA cm−2, under 266 nm). These attributes facilitate excellent self‐powered polarized‐light detection of high on/off contrast (≈103) and polarization ratio (≈2.5), beyond those of inorganic oxides (e.g. ZnO, 1.47; GaN, 1.38). This study highlights potential of 2D perovskite ferroelectrics for new optoelectronic application. [ABSTRACT FROM AUTHOR]

Oxide materials with the perovskite structure have been used in sensors and actuators for half a century, and halide perovskites transformed photovoltaics research in the past decade. Nitride perovskites have been computationally predicted to be stable, but few have been synthesized, and their properties remain largely unknown. We synthesized and characterized a nitride perovskite lanthanum tungsten nitride (LaWN3) in the form of oxygen-free sputtered thin films, according to spectroscopy, scattering, and microscopy techniques. We report a large piezoelectric response measured with scanning probe microscopy that together with synchrotron diffraction confirm polar symmetry of the perovskite LaWN3. Our LaWN3 synthesis should inspire growth of other predicted nitride perovskites, and measurements of their properties could lead to functional integration with nitride semiconductors for microelectromechanical devices. [ABSTRACT FROM AUTHOR]

The variation of leakage current and polarization hysteresis properties for bulk CH3NH3PbI3 perovskite was studied as a function of temperature to understand the reported hysteresis in photocurrent and the role of ferroelectricity. The leakage current decreased by two orders of magnitude when the temperature was lowered from 350K to 100 K. The transitions in leakage current were observed at structural phase transition temperatures. The temperature dependence study allowed the identification of current conduction mechanism based on various models for ferroelectrics and insulating materials. Our results show that the leakage current is governed by the space charge limited conduction mechanism which should be considered in addition to ion conduction and ferroelectricity when analyzing current-voltage hysteresis for thin film and bulk materials. The Mott's variable range hopping model fits well to the experimental data indicating the charge conduction is through hopping mechanism from 300K to 160K and possibly tunneling below 160 K. The conclusions from polarization hysteresis study are: (1) the hysteresis loop shape is highly dependent upon frequency and show non-saturating behavior, an indicative of strong non-ferroelectric contributions such as resistive component. (2) No domain switching current was observed between the temperature range of 100 K-350 K. (3) An electric field off-set was observed in polarization-electric field curves and it was dependent upon the frequency and temperature. This offset could be caused by the accumulation of vacancies at one interface, which could give rise to hysteresis in forward and reverse bias photocurrent. (4) The time dependence study of instantaneous current as the voltage was increased linearly show strong resistive contribution to hysteresis loop at temperatures above 200K and capacitive contribution at 100 K. [ABSTRACT FROM AUTHOR]

Due to their high potentiality for photovoltaic applications or coherent light sources, a renewed interest in hybrid organic perovskites has emerged for few years. When they are arranged in two dimensions, these materials can be considered as hybrid quantum wells. One consequence of the unique structure of 2D hybrid organic perovskites is a huge exciton binding energy that can be tailored through chemical engineering. We present experimental investigations of the exciton non-linearities by means of femtosecond pump-probe spectroscopy. The exciton dynamics is fitted with a bi-exponential decay with a free exciton life-time of ~100 ps. Moreover, an ultrafast intraband relaxation (<150 fs) is also reported. Finally, the transient modification of the excitonic line is analyzed through the moment analysis and described in terms of reduction of the oscillator strength and linewidth broadening. We show that excitonic non-linearities in 2D hybrid organic perovskites share some behaviours of inorganic semiconductors despite their high exciton binding energy. [ABSTRACT FROM AUTHOR]

The influence of uniaxial compressive stress on the small signal direct piezoelectric coefficient of hard and soft Pb(Zr,Ti)O3 at the morphotropic phase boundary was investigated as a function of temperature from 25℃ to 450℃. The stress- and temperature-dependent piezoelectric data indicate that stress is capable of either directly or indirectly modifying the orientation of polar defects in the crystal lattice and reduce the internal bias field. At higher temperatures, the mobility of polar defects was found to increase, corresponding to a two-step decrease in the direct piezoelectric coefficient and a decrease in the frequency dispersion. Quenching experiments were used to elucidate the role of the internal bias field on the stress-dependent piezoelectric response. [ABSTRACT FROM AUTHOR]

A series of polycrystalline orthorhombic manganites Sm1-xLuxMnO3 have been synthesized in order to study the magnetism-induced ferroelectricity. Detailed measurements of the magnetic and electric properties of Sm1-xLuxMnO3 (0⩽x⩽0.3) compounds have been performed. The obtained Mn-O-Mn bond angle and the Néel temperature decrease with increasing x, indicating the strengthened frustration of original A-type antiferromagnetic (A-AFM) order of Mn spins. For lower x concentrations, noferroelectricity is detected, implying the stability of the A-AFM ordering. Further increasing x, a dielectric anomaly begins to develop at 28K since x=0.15 which is not observed in SmMnO3. Coinciding with this dielectric anomaly, a ferroelectric polarization emerges, implying the multiferroicity. For intermediate compositions, a possible complex phase separation exists. [ABSTRACT FROM AUTHOR]

Sr(Ga0.7 Co0.3)O3-δ/Co perovskite/metal thin films have been systematically studied by means of Faraday and Kerr magneto-optical spectroscopies. The samples were prepared by pulsed laser deposition on (001) (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) and Si substrates, and grew as a perovskite matrix containing approximately 6% by volume of embedded metallic Co nanoparticles with diameter less than 20 nm, which were distributed throughout the film and at the film-substrate interface. The film thickness ranged from 130 to 310 nm. The perovskite matrix was single crystal on LSAT and polycrystalline on Si. The magneto-optical spectroscopy was carried out in both Faraday and Kerr configurations in the photon energy range from 0.5 to 5 eV in magnetic fields sufficient for sample saturation, showing a strong thickness dependence of the magneto-optical effect. This dependence was attributed to the different metallic Co content, nanoparticle size, and accumulation at the film-substrate interface. [ABSTRACT FROM AUTHOR]

[Display omitted] • Enhanced C 3 H 8 oxidation activity of perovskites etched by oxalic acid. • Abundant Co2+ Lewis acid sites with reactive dangling bonds after etching. • Better reducibility and oxygen activation ability ascribed to more Co2+ sites. • More facile C 3 H 8 adsorption and activation due to the population of Co2+ sites. Perovskite oxides have emerged as promising alternatives for the supported Platinum group metal catalysts for total oxidation of propane and other volatile organic compounds (VOC). Here, we report a surface modification method to improve propane oxidation activity of La 0.8 Sr 0.2 CoO 3 monolithic catalysts using diluted oxalic acid etching. The oxalic acid treatment decreases the light-off temperatures of propane oxidation by 30–40 °C. Experimental and DFT investigations reveal that the treatment selectively etches Sr cations and slightly reduces LSCO surface, leading to an increased population of low-valence Co2+ Lewis acid sites, which promotes activation of lattice oxygen and adsorbed oxygen species and facilitates propane adsorption and dissociation. Our work offers a rapid strategy to activate perovskite monolithic catalysts and will inspire the research on surface modification of perovskite catalyst. [ABSTRACT FROM AUTHOR]