Perovskite Compounds Research Articles

Over 12% efficient CsSnI3 perovskite solar cells enabled by surface post-treatment with bi-functional polar molecules

Eco-friendly all-inorganic tin halide perovskite compounds have drawn significant attention for photovoltaic applications. Nevertheless, the non-radiative recombination derived from the uncoordinated Sn2+ cations at surface and the electron extraction barrier between different functional layers significantly impair the performance of perovskite device. Here we for the first time show that thiophene derivative, 3-thiophenemethylammonium iodide, as an interface modifier between the CsSnI3 perovskite surface and electron transport layer, can passivate defects and reduce the electron extraction potential barrier. The molecules of 3-thiophenemethylammonium iodide can autonomously inter-connect with uncoordinated Sn2+via lone electron pairs of the donated π electrons in electronic-rich thiophene molecule. Moreover, such interface modifier lowers the electron extraction potential barrier at the perovskite/electron transport layer junction in which an interface dipole electric field form. Consequently, the optimized planar solar cell with a structure of ITO/PEDOT:PSS/CsSnI3/ICBA/BCP/Ag, exhibited a power conversion efficiency of 12.05 % under AM 1.5G illumination condition. To the best of our knowledge, this is the highest efficiency for fully inorganic CsSnI3-based devices reported so far. This study represents an innovative approach to realize high-efficiency all-inorganic CsSnI3 perovskite solar cells.

Effect of Covalence and Degree of Cation Order on the Luminous Efficacy of Mn4+ Luminescence in the Double Perovskites, Ba2BTaO6 (B = Y, Lu, Sc).

The spectroscopic properties of the Mn4+ ion are investigated in the series of isostructural double perovskite compounds, Ba2BTaO6 (B = Y, Lu, Sc). A comparison of these properties highlights the influence of covalent bonding within the perovskite framework and the degree of order between the B3+-Ta cations on the energy and intensity of the Mn4+2E → 4A2 emission transition (R-line). These two parameters of the emission spectrum are of importance for practical application since they determine the phosphor luminous efficacy. The influence of covalent bonding within the corner shared BO6/2 and TaO6/2 perovskite framework on the energy of the R-line energy is investigated. From the spectroscopic data, we have derived information on the influence of the degree of order between the B3+ and Ta5+ cations on the intensity of the R-line. The lowest energy and the highest intensity of the R-line are found in the double perovskite, Ba2ScTaO6. The purpose of this work is to propose for first time an explanation of these effects in the considered double perovskites. The obtained results are useful guidelines for practical improvement and tuning of key parameters of phosphors to the desired values.

Intrinsic Room-Temperature Ferromagnetism in New Halide Perovskite AgCrX3 (X: F, Cl, Br, I) Using Ab Initio and Monte Carlo Simulations.

Herein, we present a detailed comparative study of the structural, elastic, electronic, and magnetic properties of a series of new halide perovskite AgCrX3 (X: F, Cl, Br, I) crystal structures using density functional theory, mean-field theory (MFT), and quantum Monte Carlo (MC) simulations. As demonstrated by the negative formation energy and Born-Huang stability criteria, the suggested perovskite compounds show potential stability in the cubic crystal structure. The materials are ductile because the Pugh's ratio is greater than 1.75, and the Cauchy pressure (C12-C44) is positive. The ground state magnetic moments of the compound were calculated as 3.70, 3.91, 3.92, and 3.91 μB for AgCrF3, AgCrCl3, AgCrBr3, and AgCrI3, respectively. The GGA + SOC computed spin-polarized electronic structures reveal ferromagnetism and confirm the metallic character in all of these compounds under consideration. These characteristics are robust under a ±3% strained lattice constant. Using relativistic pseudopotentials, the total energy is calculated, which yields that the single ion anisotropy is 0.004 meV and the z-axis is the hard-axis in the series of AgCrX3 (X: F, Cl, Br, and I) compounds. Further, to explore room-temperature intrinsic ferromagnetism, we considered ferromagnetic and antiferromagnetic interactions of the magnetic ions in the compounds by considering a supercell with 2 × 2 × 2 dimensions. The transition temperature is estimated by two models, namely, MFT and MC simulations. The calculated Curie temperatures using MC simulations are 518.35, 624.30, 517.94, and 497.28 K, with ±5% error for AgCrF3, AgCrCl3, AgCrBr3, and AgCrI3 compounds, respectively. Our results suggest that halide perovskite AgCrX3 compounds are promising materials for spintronic nanodevices at room temperature and provide new recommendations. For the first time, we report results for novel halide perovskite compounds based on Ag and Cr atoms.

Optical and dielectric properties of divalent copper based double perovskite compound, Gd2CuTiO6

In this work, we have investigated high temperature dielectric properties and room temperature optical properties on rare earth ion based orthorhombic Gd2CuTiO6 (GCTO). Optical properties like reflectance and band gap were determined from ultra-violet visible (UV–Vis) diffuse reflectance spectroscopy technique and photoluminescence (PL) spectrum. The compound exhibited substantial optical absorption and emission in the visible region. Our findings reveal the presence of an intermediate band, as evidenced by the difference between the band gap values obtained from the Tauc plot using the diffuse reflectance spectrum (3.07 eV) and the PL spectrum (2.4 eV). Furthermore, thermogravimetric analysis demonstrated high thermal stability with <0.4% change in mass over a wide temperature range of 30 °C–1200 °C in air environment. Moreover, lead-halide free compound, GCTO is highly thermally stable oxide double perovskite with wide band gap and absorption in the UV–Vis range are highly suitable for optical applications In addition, dielectric properties of the compound have been examined using impedance spectroscopy as a function of frequency ranging from 500 Hz to 1 MHz and temperature between 300 K and 550 K. Compounds with relaxor behaviour at high temperatures and high thermal stability are desired for several applications. Because of the cation disorders present in this compound, GCTO displays dielectric relaxor behaviour indicative of a distribution of relaxation times. Furthermore, the frequency-dependent modulus illustrated a thermally activated conduction mechanism. Cole–Cole plots of electrical modulus suggest prominent grain contribution above 350 K.

High‐Performance White Emission from Cu‐Based Perovskite Compound

AbstractThe white emissions based on lead‐free perovskites with broadband emission due to self‐trapped excitons (STEs) are considered as an ideal candidate for next‐generation white light‐emitting diodes (WLEDs). Recently, copper‐based halide perovskites Cs3Cu2I5@CsCu2I3 composites films with a high color‐rendering index (CRI) have been developed for WLEDs. However, the Cs3Cu2I5@CsCu2I3 composites generally exhibit a relatively low photoluminescence quantum yield (PLQY). Herein, a high PLQY up to 86.75% copper‐based perovskite Gua3Cu2I5 (Gua = guanidine) films with a broadband strong yellow STEs emission centered at 544 nm is synthesized. By combining with efficient blue STEs emission Cs3Cu2I5 component via composition engineering of Cs3Cu2I5@Gua3Cu2I5, a high PLQY of up to 96.1% is achieved on the white emission composites films. Moreover, a high CRI of 93 WLEDs is achieved by integrating Cs3Cu2I5@Gua3Cu2I5 composites film onto a UV LED chip. These findings provide a simple and effective strategy for designing highly efficient white light‐emitting diodes.

Revealing the Structural, Elastic, Electronic, and Optical Properties of K2ScCuCl6 and K2YCuCl6: An In-Depth Exploration Using Density Functional Theory.

The optoelectronic, structural, and elastic properties of K2ScCuCl6 and K2YCuCl6 double perovskite compounds were thoroughly investigated in this study using density functional theory. It is observed that both compounds exhibit exceptional structural and mechanical stability. The structural stability is assessed using Goldsmith's tolerance factor (tG), with values approaching unity indicating a reliable cubic perovskite structure. Phonon stability was ensured by the absence of negative energy formations and only real frequencies in the phonon calculations. Applying the finite displacement method also provided further evidence of the compounds' thermodynamic stability. The electronic properties analysis revealed that K2ScCuCl6 and K2YCuCl6 are narrow band gap semiconductors, with band gap values of 1.8 and 2.5 eV, respectively. This was confirmed by analyzing the density of states. Furthermore, the optical properties exhibited transparency at lower photon energies and significant absorption at higher energies. These exciting findings suggest that K2ScCuCl6 and K2YCuCl6 have promising applications in high-frequency UV devices.

High-pressure synthesis and magnetic characterization of quadruple perovskites SmA′3Co4O12 (A′ = Cu, Mn)

In this study, two novel quadruple perovskite compounds SmA′3Co4O12 (A′ = Cu, Mn) were synthesized using a high-pressure synthesis method. Structural analysis of the perovskites using synchrotron X-ray powder diffraction revealed that both SmCu3Co4O12 and SmMn3Co4O12 have cubic Im3‾ structure. In the temperature range of 2–300 K, SmCu3Co4O12 did not exhibit a magnetic phase transition, whereas SmMn3Co4O12 exhibited a paramagnetic to ferrimagnetic phase transition at ∼90 K. A comparison of structural information, X-ray absorption near edge structure, and magnetic properties revealed that the low-spin state (S = 0) characterizes the spin state of Co3+ when the A′ site is occupied by Cu3+. However, when the A′ site is occupied by Mn3+, the Co3+ spin state is in a high-spin state (S = 2), indicating that a long-range magnetic phase transition occurs owing to the magnetic interaction between the Mn and Co ions.

A DFT insight into the physical features of alkaline based perovskite compounds AInBr3 (A = K, Rb)

Owing to their proper characteristic, simple halide perovskites became engaged over time for thermoelectric applications. In this work, several physical properties of simple halide perovskite materials AInBr3 (A = K, Rb) are predicted based on density functional theory (DFT) within the Wien2k code. The tolerance factor and negative formation energy demonstrate the stability and formation of these compounds, and the Born criteria shows their mechanical stability and inherent ductility. Notably, the modified Becke-Johnson potential (mBJ) was used to calculate the optoelectronic characteristics. The AInBr3 (A = K, Rb) perovskites present semiconducting aspects. Analyses of their optical characteristics, including refractive index, reflectivity, were performed. AInBr3 (A = K, Rb) transport properties were studied. The highest figure of merit was attained by AInBr3 (A = K, Rb) which had a high Seebeck coefficient and high electrical conductivity. Finally, all studied properties of simple halide perovskites give a new way for efficient applications in thermoelectric.

Ba6RE2Ti4O17 (RE = Nd, Sm, Gd, Dy-Yb): A Family of Rare-Earth-Based Layered Triangular Lattice Magnets.

The exploration of new rare-earth (RE)-based triangular-lattice materials plays a significant role in motivating the discovery of exotic magnetic states. Herein, we report a family of hexagonal perovskite compounds Ba6RE2Ti4O17 (RE = Nd, Sm, Gd, Dy-Yb) with a space group of P63/mmc, where magnetic RE3+ ions are distributed on the parallel triangular-lattice layers within the ab-plane and stacked in an 'AA'-type fashion along the c-axis. The low-temperature magnetic characterizations indicate that all synthesized Ba6RE2Ti4O17 compounds exhibit dominant antiferromagnetic (AFM) interactions and the absence of magnetic order down to 1.8 K. The isothermal magnetization and electron spin resonance results reveal the distinct magnetic anisotropy for the compounds with different RE ions. Moreover, the as-grown Ba6Nd2Ti4O17 single crystals exhibit Ising-like magnetic anisotropy with a magnetic easy-axis perpendicular to the triangle-lattice plane and no long-range magnetic order down to 80 mK, as the quantum spin liquid candidate with dominant Ising-type interactions.

Comments on the paper “Development of a novel triple perovskite barium bismuth molybdate material for thermistor-based applications”

The title paper (Materials Science & Engineering B 296 (2023) 116616) claimed the preparation and detailed characterization by different methods of a novel triple perovskite compound, Ba3Bi2MoO9. In this comment, it is shown that the phase Ba3Bi2MoO9 does not exist. We show that the absence of the phase analysis resulted in erroneous claims. We demonstrate that the sample in the title paper is mainly a mixture of BaBiO3 and BaMoO4.

Electronic structures of lead-free Sn- or Ge-hybrid perovskite halides studied by first-principles calculation

Although CH3NH3PbI3-based perovskite compounds have excellent photovoltaic properties, the lead (Pb) is harmful to the environment, and Pb-free perovskite compounds are needed for next generation solar cells. Theoretical calculations could be one of the good methods to design the Pb-free compounds, and the first-principles calculation was used to predict the properties of the present proposed materials. The instability of organic molecules such as CH3NH3 is also a problem, and alkali elements such as cesium and rubidium could improve the stability. From these point of view effects of tin (Sn) or germanium (Ge) on the lead-free Cs- or Rb- -based perovskites including double perovskite structures were investigated by first-principles calculation in the present work. For the standard single perovskite structures, perovskites with chlorine have suitable band gap energies, higher electron mobilities, and photovoltaic performance compared with other iodine or bromine-based perovskites. For the double perovskite structures, bromine was found to be the suitable halogen, and Ge provided a higher electron density than Sn. The double perovskite structures also provided wider band gap energies and improved stability compared with the standard single perovskites, and the photovoltaic properties could be affected by hybridization of Sn/Ge or halogen ions.

Influence of doping concentrations on the structural, optical, and magnetic properties of Ba-doped LaCoO3 nanostructure

Abstract In this article we report the structural, morphology, vibrational, optical and magnetic properties of Ba x La1−x CoO3 (x = 0, 0.05, and 0.1) (LBCO) samples. The X-ray diffraction shows that samples are in single rhombohedral phase. The Raman signals of LCO were quite small in comparison to LBCO, which exhibited a Raman peak above 675 cm−1. The band seen with a wavenumber of 484 cm−1 corresponds to the vibrational modes of E g bending and Ba–O stretching. UV–DRS and photoluminescence spectra indicated broad absorption over the ultraviolet, visible, and near-infrared spectrums. Surface morphology and EDAX spectra corroborated the materials homogeneous size distribution and homogenous microstructure, with Ba indicating a more stable structure. XPS was used to study chemical states of LBCO and found Co (2p), La (3d), O (1s), and C (1s) elements in perovskite compounds. A peak beneath 300 eV indicated adventitious carbon on surface materials. XPS survey spectrum elements La, Ba, Co, and O had their own binding energies. The magnetization-field dependency of LBCO at 300 K showed that Ba insertion into the LCO switched it from paramagnetic to weak ferromagnetic. Ba considerably decreased magnetic saturation and coercivity, influencing magneto-crystallites’ anisotropy and coercive field.

Titanate-based high-entropy perovskite oxides relaxor ferroelectrics

Different combinations of monovalent and trivalent A-cations in high-entropy perovskite oxides (HEPOs) were investigated. The multicomponent (A′0.2A″0.2Ba0.2Sr0.2Ca0.2)TiO3 (A′ = Na+, K+, A″ = Bi3+, La3+) perovskite compounds were successfully synthesized by solid-state reaction method persisting average cubic perovskite phase. The trivalent cation exhibited distinct effects on local structure, dielectric properties and relaxor ferroelectric behavior. Highly dense ceramics (> 95%), high dielectric constant (~ 3000), low dielectric loss (~ 0.1), and relaxor ferroelectric characteristics were obtained in the compound containing Bi3+. The La3+ containing compounds revealed lower dielectric constant, higher dielectric loss and linear dielectric behavior. The effect of monovalent cation on the dielectric properties was minimal. However, it affected relaxor ferroelectric behavior at elevated temperatures and conduction behavior at high temperatures. The (K0.2Bi0.2Ba0.2Sr0.2Ca0.2)TiO3 ceramic maintained the relaxor ferroelectric behavior with low PREM at high temperatures suggesting more stable relaxor ferroelectric characteristics than that of the (Na0.2Bi0.2Ba0.2Sr0.2Ca0.2)TiO3. Moreover, between these two compounds, the homogeneous electrical characteristics could be obtained from the compound consisting of K + and Bi + at A-site. This study suggests that tuning the chemical composition, particularly choosing appropriate combination of mono/trivalent cations in high entropy perovskite oxides, could be the effective approach to develop high-performance relaxor ferroelectrics with the desired properties.

Predicting structural, elastic, and optoelectronic properties of oxide perovskites HfXO3 (X =Be, Mg) employing the DFT approach

This study conducts a comprehensive exploration of the structural, electronic, elastic, and optical properties of HfXO3 (X=Be, Mg) perovskite compounds, employing density functional theory (DFT) within the WIEN2k code. Employing the Birch Murnaghan fitting technique, our structural evaluation establishes the structural stability of these materials, with optimized lattice constants underscoring their stability at specific values. By harnessing the capabilities of the IRelast software, we have determined elastic constants and characterized the anisotropic tendencies, disclosing that both compounds exhibit a pronounced degree of anisotropy. Moreover, an in-depth investigation into electronic attributes, facilitated by the modified Becke–Johnson potential, uncovers these materials as indirect narrow band gap semiconductors, with calculated band gaps of 1.14 eV for HfBeO3 and 0.8 eV for HfMgO3 serving as vital indicators of their electronic character. Furthermore, we delve into the optical traits of these materials, revealing their photon transparency within the energy spectrum of 0 eV to 15 eV. These key optical properties encompass dielectric functions, refractive index, optical conductivity, absorption coefficient, extinction coefficient, energy loss function, and reflectivity. This comprehensive exploration offers a holistic understanding of the optical behaviors exhibited by these materials. By skillfully combining structural, electronic, elastic, and optical analyses, this study significantly contributes to the comprehension of HfXO3 (X=Be, Mg) perovskites, forging a path for their potential applications and serving as a foundation for future research endeavors.

Synthesis and characterization of Cs2TiX6 (X = Cl, Br) double perovskites for photocatalytic dye degradation

Massive efforts have been undertaken for better utilization of solar energy in environmental and energy applications. The creation of environmentally friendly, economically viable and chemically efficient processes is today’s key chemistry challenge. The primary goal of this study is to synthesize and confirm the viability of lead-free halide perovskite for photocatalytic efficiency in the degradation of organic dyes – namely, eosin B and eosin Y – in water solutions when exposed to visible light. The lead-free cesium titanium halide Cs2TiX6 (X = Cl, Br) double-perovskite compound was successfully synthesized using the solution-processing method. The effective synthesis of perovskite photocatalysts was confirmed by various optical, morphological and structural characterization techniques, such as X-ray diffraction, ultraviolet–visible spectroscopy, photoluminescence spectroscopy, zeta potential measurement, scanning electron microscopy and transmission electron microscopy. Positive zeta values reveal that the generated photocatalyst is functional with the adsorption of anionic dyes. The photodegradation efficiency of eosin Y by the synthesized perovskite photocatalysts is substantially higher than that of eosin B. The photocatalytic degradation efficiencies of Cs2TiCl6 and Cs2TiBr6 perovskite photocatalysts are 59.12 and 48.77% for eosin B and 72.35 and 89.94% for eosin Y, respectively.

Structural, electrical and optical investigation of half doped YTi0.5Mn0.5O3 perovskite compounds for optoelectronic devices

Structural, electrical and optical investigation of half doped YTi0.5Mn0.5O3 perovskite compounds for optoelectronic devices

Novel ternary halide perovskite AMX3(A/M=Li, Na, K, Rb, Be, Mg, Ca, Sr, Ba, X=Br, Cl, F, I) for optoelectronic applications

In this article, we present the first principle calculations on 40 AMX3 perovskite compounds - AMX3 composition, where X = Br, Cl, F or I, and M = an alkali or alkali-earth elements. These compounds are not reported until now either theoretically or experimentally. From the literature reports of ANN, the structures were relaxed for minimum energy, and the optimized lattice constants were used to perform calculations for GGA_PBE. In this work, apart from the novel AMX3 compound's structural and electronic property investigation, we are interested in studying the impact of spin and orbital angular momentum of electrons over these AMX3 materials. So, SOC and TB_mBJ have been included in this work. The results of volume optimization, i.e., bulk modulus, pressure derivative, volume, and total energy, are tabulated. The four cases of study GGA_PBE, GGA_PBE+SOC, GGA_PBE+TB_mBJ, and GGA_PBE+SOC+TB_mBJ are compared for all the 40 compounds. The trends the band gap exhibits are studied for halides, alkalis, and alkali-earth elements. Among the compounds, the band gap of seven of the compounds studied in this work matches approximately with the Schockley-Queisser limit(Eg≈1.34 eV). The compounds presented and discussed in this article can potentially contribute to advancements in solar cell and semiconductor research.

Visualizing the Low-Energy Electronic Structure of Prototypical Hybrid Halide Perovskite through Clear Band Measurements.

Organic-inorganic hybrid perovskites (OIHPs) are a promising class of materials that rival conventional semiconductors in various optoelectronic applications. However, unraveling the precise nature of their low-energy electronic structures continues to pose a significant challenge, primarily due to the absence of clear band measurements. Here, we investigate the low-energy electronic structure of CH3NH3PbI3 (MAPI3) using angle-resolved photoelectron spectroscopy combined with ab initio density functional theory. We successfully visualize the electronic structure of MAPI3 near the bulk valence band maximum by using a laboratory photon source (He Iα, 21.2 eV) at low temperature and explore its fundamental properties. The observed valence band exhibits a highly isotropic and parabolic band characterized by small effective masses of 0.20-0.21 me, without notable spectral signatures associated with a large polaron or the Rashba effect, subjects that are intensely debated in the literature. Concurrently, our spin-resolved measurements directly disprove the giant Rashba scenario previously suggested in a similar perovskite compound by establishing an upper limit for the Rashba parameter (αR) of 0.28 eV Å. Our results unveil the unusually complex nature of the low-energy electronic structure of OIHPs, thereby advancing our fundamental understanding of this important class of materials.

Exploring the structural, electronic and optical properties of Rb2InGaCl6 and Rb2InGaF6 double perovskite compounds for high-energy applications: a DFT-based investigation

Exploring the structural, electronic and optical properties of Rb2InGaCl6 and Rb2InGaF6 double perovskite compounds for high-energy applications: a DFT-based investigation

High-Throughput Ensemble-Learning-Driven Band Gap Prediction of Double Perovskites Solar Cells Absorber

Perovskite materials have attracted much attention in recent years due to their high performance, especially in the field of photovoltaics. However, the dark side of these materials is their poor stability, which poses a huge challenge to their practical applications. Double perovskite compounds, on the other hand, can show more stability as a result of their specific structure. One of the key properties of both perovskite and double perovskite is their tunable band gap, which can be determined using different techniques. Density functional theory (DFT), for instance, offers the potential to intelligently direct experimental investigation activities and predict various properties, including band gap. In reality, however, it is still difficult to anticipate the energy band gap from first principles, and accurate results often require more expensive methods such as hybrid functional or GW methods. In this paper, we present our development of high-throughput supervised ensemble learning-based methods: random forest, XGBoost, and Light GBM using a database of 1306 double perovskites materials to predict the energy band gap. Based on elemental properties, characteristics have been vectorized from chemical compositions. Our findings demonstrate the efficiency of ensemble learning methods and imply that scientists would benefit from recently employed methods in materials informatics.