Perovskite Type Research Articles

Enhancing Stability of Microwave-Synthesized Cs2SnxTi1-xBr6 Perovskite by Cation Mixing.

The double-perovskite material Cs2TiBr6 shows excellent photovoltaic potential, making it a promising alternative to lead-based materials. However, its high susceptibility to degradation in air has raised concerns about its practical application. This study introduces an interesting synthesis approach that significantly enhances the stability of Cs2TiBr6 powder. We implemented a gradual cation exchange process by substituting Ti4+ with Sn4+ in the efficient microwave-assisted synthesis method, developing a double perovskite Cs2SnxTi1-xBr6 type. A systematic study of increasing concentration of Sn4+ in Cs2TiBr6 perovskite has been performed to analyze the effect of Sn-doping degree on the chemical and thermal stability of the material and the optical features in both nitrogen and ambient atmospheres, significantly increasing the stability of the material in the air for over a week. Furthermore, introducing Sn4+ results in a more uniform polygonal crystal morphology of the powders and a slight band gap broadening. We show that microwave-assisted synthesis is highly efficient and cost-effective in producing more sustainable lead-free perovskite materials with enhanced stability and desirable electrical characteristics. This work suggests a promising method for synthesizing perovskite materials, opening new routes for scientific research and applications.

Enhanced Efficiency and Stability of Triple-Cation Perovskite Solar Cells through Engineering of the Cell Interface with Phenylethylammonium Thiocyanate.

It is reported that the tricationic mixed halide perovskite Csx(FAyMA1-y)1-xPb(IzBr1-z)3 (CsFAMA) possesses a stable crystal structure and outstanding bandgap tunability, rendering it one of the most competitive candidates for commercial perovskite solar cells (PSCs). Nevertheless, the numerous defects at the interface of the tricationic perovskite give rise to a significant constraint on the light capture performance of the device. Simultaneously, water molecules form intermediate compounds with the perovskite at the interface via hydrogen bonds, accelerating the degradation of the perovskite. This study reports the introduction of two-dimensional (2D) phenylethylthiocyanate (PEASCN) at the interface of three-dimensional (3D) perovskite. This approach significantly passivates the surface defects of the perovskite. Concurrently, due to the propensity of the organic ammonium cation PEA+ to interact with the FA+ base within the perovskite, SCN- is exposed outward to form a small-molecule hydrophobic layer. This method markedly reduces the loss of charge recombination and significantly enhances the device stability. The results indicate that the efficiency of the conventional device treated solely with PEASCN is as high as 23.94%. The unsealed device retains 85.12% of its initial efficiency after being placed in a conventional environment for 500 h. Furthermore, this surface passivation and hydrophobic strategy can be universally applicable to perovskite types with a high FA+ content.

Enhancing NH3-SCR denitrification performance through synergistic A- and B-site effects via CeFe modification of LaMnO3

ABO3 type perovskite catalysts are widely used in NH3-SCR to remove NOx due to excellent low-temperature reduction performance. To study the synergistic effect of A and B sites on the structure, morphology and redox performance of modified perovskite catalysts (La1-xCexMn1-yFeyO3), LaMnO3 perovskite catalysts were co-doped with CeFe by sol-gel method, and the crystal structure, surface chemical environment, optimal metal co-doping ratio and surface adsorption of the modified perovskite catalysts were clarified through various characterizations. In addition, through first-principles calculations, the differential charge density and binding energy of each doping system were analyzed, the relationship between the difficulty of Ce doping and the electronic population of Mn atoms and the redox ability of the catalyst was discussed, and the key bond types and their changing rules in perovskite catalytic reduction were clarified. The results showed that co-doping Ce and Fe could improve the denitrification efficiency and sulfur resistance of the catalyst. When the Fe doping ratio is 0.1, the denitrification activity is the highest. Among them, the La0.9Ce0.1Mn0.9Fe0.1O3 catalyst showed the most favorable active acid site distribution and the best reduction performance, which was conducive to the adsorption and redox of gas molecules on the catalyst surface. At the same time, when the A and B sites were co-doped, the electron transferred mainly occurs between Ce ions and Fe ions, forming a synergistic effect and changing the covalent components between Mn-O and Fe-O bonds. This made the valence states of Mn and Fe ions more, enhanced the catalytic activity of perovskite, and promoted the redox of NO on the catalyst surface, thus providing a new idea for the redox reaction pathway of modified perovskite catalysts.

Microscopic mechanism of water-assisted diffusional phase transitions in inorganic metal halide perovskites.

The stability of perovskite materials is profoundly influenced by the presence of moisture in the surrounding environment. While it is well-established that water triggers and accelerates the black-yellow phase transition, leading to the degradation of the photovoltaic properties of perovskites, the underlying microscopic mechanism remains elusive. In this study, we employ classical molecular dynamics simulations to examine the role of water molecules in the yellow-black phase transition in a typical inorganic metal halide perovskite, CsPbI3. We have demonstrated, through interfacial energy calculations and classical nucleation theory, that the phase transition necessitates a crystal-amorphous-crystal two-step pathway rather than the conventional crystal-crystal mechanism. Simulations for CsPbI3 nanowires show that water molecules in the air can enter the amorphous interface between the black and yellow regions. The phase transition rate markedly increases with the influx of interfacial water molecules, which enhance ion diffusivity by reducing the diffusion barrier, thereby expediting the yellow-black phase transition in CsPbI3. We propose a general mechanism through which solvent molecules can greatly facilitate phase transitions that otherwise have prohibitively high transition energies.

Mitigating bulk halide defects in blue-emissive perovskite nanocrystals using benzoyl halides for efficient light-emitting diodes

While recent advances have demonstrated highly efficient and stable perovskite light-emitting diodes (LEDs), blue perovskite LEDs still show low performance compared to green, red, near IR counterparts. Despite perovskites being well-known for their defect tolerance, blue perovskites are highly vulnerable to defects, which introduce deep trap states. In this study, we mitigated bulk halide vacancies in perovskite nanocrystals (PNCs) via the diffusion-assisted halide repairing strategy. We confirmed halide vacancies inside as-synthesized PNCs, both in the core and on the surface, through HADDF-STEM. By treating PNCs with benzoyl halides, these halide vacancies were further mitigated due to halide diffusion via concentration gradients between the surface and the core, resulting in enhanced PLQY of the PNCs. In the fabrication of blue PNCs LEDs, this approach yielded a comparable efficiency with an EQE of 5.37 % at 469 nm, demonstrating the robustness of our method for efficient blue perovskite LEDs. Furthermore, the peak wavelengths of benzoyl halide-treated PNCs LEDs remained stable during operation, whereas those of pristine PNC LEDs exhibited peak shifts. We believe that our novel approach can be universally applied to various types of perovskites, reducing bulk vacancies. This advancement will be a significant breakthrough for the performance enhancement of blue perovskite LEDs in the future.

Implementing Lattice and Energy Level Matching to Optimize Buried Interfaces for High-Performance Perovskite Solar Cells.

In n-i-p type perovskite solar cells (PSCs), mismatches in energy level and lattice at the buried interface is highly detrimental to device performance. Here, thin PbS interconnect layer in situ coating on the SnO2 surface is grown. The function of PbS at the interface is different from the commonly used function of crystalline seeds in perovskite bulk. The theoretical calculation show that it helps construct an interconnect structure of SnO2/PbS/Perovskite with matched energy level and lattice. This not only increases conductivity of SnO2, but also upshifts Fermi energy levels (EF) of both SnO2 and buried perovskite due to charge transfer and perovskite's internal defect changes. Such a suitable energy level arrangement ensures a better energy level match at the interface, favoring efficient charge transfer and less open circuit voltage (Voc) loss. Additionally, in situ PL reveals that the template effect of PbS enable perovskite grain to grow bottom-up because of their highly matched lattice parameters. This growth mode optimizes buried interface contact and crystallinity of perovskite. Ultimately, after PbS modification, a remarkable power conversion efficiency (PCE) exceeding 24% and better device stability are obtained. This work demonstrates an effective interconnect layers strategy to realize ideal interface contact toward high-performance PSCs.

Enhanced performance of perovskite solar cell by optimization of thin film control parameters using Taguchi method

The objective of the study is to examine the influence of various thin film control parameters on the synthesis of carbon-based passivated perovskite solar cells. Passivation additives, namely MOF UiO-66-NH2 (20 mg/ml) and inorganic additive KPF6 (1 mg/ml), were applied to treat the perovskite solar cells simultaneously. A PSC device of a standard configuration FTO/TiO2/Perovskite layer/Additives/HTL/Carbon electrode is utilized for experimentation. The performance evaluation of the system was carried out using Taguchi method. The critical control parameters considered in the study are: type of perovskite; annealing temperature of perovskite layer; the number of perovskite coating layers; and the type of hole transport layer (HTL). Each parameter is allocated three levels. An orthogonal array was designed using the Taguchi technique to optimize the quality control parameters. The signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were then utilized to determine the ideal combination of parameters. The analysis identified the significant contribution of each parameter to the efficiency of perovskite cells. Among these parameters, the type of perovskite (used in the synthesis process) was found to impact the fabrication and performance of the cells significantly. Furthermore, it was observed that the type of hole transport layer (HTL) employed in the device significantly influences its performance. The best combination for our experiment is found to have FA0.55MA0.25Cs0.20PbI3 as the perovskite-type, an annealing temperature of 120˚C, a double layer of perovskite coating and Spiro-OMeTAD as the HTL. The solar cell is developed for each experiment as well as the validation test.

2D layered halide perovskite for field-effect transistors

Field-effect transistors are crucial components for modern electronics, generating significant research and profitable interest. Metal halide perovskites have recently emerged as a pioneering active material in solar cells, generating interest in their potential use in other electronic and (opto)electronic devices, including field-effect transistors and phototransistors. However, before they can be commercialized, they still face significant challenges owing to their immanent instabilities with respect to heat, moisture, and light. In contrast, due to their exceptional environmental stability, the newly emerging two-dimensional Ruddlesden–Popper type perovskites have garnered significant recognition. The current state of the field is covered in this review article, as are the problems, and a perspective for the scenarios of perovskite field-effect transistors. The effects of temperature, light, and measurement conditions are taken into account, as well as the physics of the device and the fundamental mechanisms that drive these devices, such as ion migration and ionic defects. Subsequently, the performance of perovskite transistors and phototransistors described so far is analyzed and critically evaluated. Finally, the major roadblocks to perovskite transistor advancement are identified and explored. The lessons learned from other perovskite optoelectronic devices are investigated in order to address these obstacles and bring these devices closer to industrial implementation.

Broad spectrum catalysis using Ca3Sn2S7 Ruddlesden-Popper perovskite under multi-stimulus

Advanced oxidation processes emerged as effective alternatives to traditional approaches. The efficacy of these methods significantly depends on the intrinsic properties of a catalyst material. Semiconductor materials with robust photo absorption alongside inherent polarization emerged as subjects of great interest. In this study, we synthesized two-dimensional Ca3Sn2S7 nanosheets oriented as Ruddlesden-Popper type perovskite structure. The optimal compositions of these nanosheets exhibit excellent physical and optical characteristics while varying Sn ratios significantly impact the properties. Impressively, these compositions boast a wide optical window that spans from the visible to the far infrared region, featuring a narrow bandgap of approximately 0.6 eV. Band potentials in a positive regime make it highly favorable for the oxidation process. The electrochemical analysis further validates high mobility with low resistance in both compositions. The catalytic efficiency of the synthesized nanosheets is evaluated using rhodamine-B. Three energy sources, i.e., visible light, laser, and ultrasound vibrations, decomposed 96 %, 90 %, and 78 %, respectively, in 30 min. Remarkably accelerated degradation rates are achieved under each stimulus, owing to the presence of oxidative optical bands, large surface area, and potential internal polarization within the nanosheets. Preliminary findings strongly indicate the immense potential of this compound in catalytic and photovoltaic applications.

Metals doping effect of perovskite–type La-Mn oxides for NH3-SCR reaction at low temperature

Doping of perovskites with the heteroatoms has emerged as an additional lever, a dimension beyond structural perfection and compositional distinction, for the alteration of many properties of perovskites. In this work, a series of different metals were doped via citric acid sol–gel method to investigate their influences on the structure and catalytic performance of La-Mn perovskite oxides for NH3-SCR reaction. It is found that Zr doped La-Mn oxides (LMZr) displays better low-temperature deNOx performance (T90 = 118 °C) than other metal doped catalysts. Such a result is mainly attributed to the increase of Lewis acid sites, surface Mn4+ and adsorbed oxygen species. Besides, La-Mn perovskite doped with Sr, Ce, Y and Al can also obviously improve low-temperature deNOx activity and N2 selectivity. These doped metals mainly change the electron transfer between different cations, thus changing the valence distribution of Mn on the surface, meanwhile, metal doping changes the crystalline size of the catalysts, thereby affecting the adsorption and activation of NH3 and O2 involved in the removal of NO. Although other metal doping alters the tolerance of the La-Mn catalyst to SO2 and/or H2O, SO2 is inevitably oxidized to S6+ and deposits on the catalyst surface. Zr or Ce doping significantly enhances the tolerance to SO2 and/or H2O, but they have a different mechanism. Zr reduces the deposition rate of sulfate while Ce reacts with SO2 to form Ce2(SOx)3 to protect Mn active species. This paper highlights the importance of Lewis acid, Mn4+ content and adsorbed oxygen in the NH3-SCR reaction.

Harnessing perovskite materials for water decontamination: a comprehensive review.

Perovskites have recently emerged as a promising class of materials with a wide range of applications, including solar cells, light-emitting diodes, and catalysts. In addition, perovskites have demonstrated significant potential for water decontamination due to their tunable properties and facile synthesis. This review article provides a comprehensive overview of perovskites, including their preparation techniques, crystal structure, and electronic properties. The article also highlights the various applications of perovskites, with a particular focus on their use in water decontamination. The different types of perovskites for water decontamination, including simple, substituted, and doped perovskites, as well as nanoscopic and supported perovskites, are discussed in detail. Furthermore, the article addresses the beneficial costs of perovskites and the environmental impacts associated with their use, including toxicity and end-of-life management. The aim of this review article is to provide a broad perspective on perovskites and their potential for water decontamination, as well as future prospects and challenges in various applications.

Experimental magnetic-semiconductor features of the theoretically half-metallic perovskite CaLaTiFeO6

Abstract In this manuscript, the synthesis process of the CaLaTiFeO6 material is shown. The crystallographic structure analysis reveals its monoclinic perovskite type nature (space group P21/n, #14), its morphological strongly granular characteristics, its optical response yields its semiconducting character with a 0.61 eV bandgap and its ferromagnetic property at temperatures T>350 K are reported. Likewise, calculations and analysis of the electronic properties are performed through Density Functional Theory, which showed correlation with the experimental results. The results allow classifying the CaLaTiFeO6 material as a ferromagnetic semiconductor at room temperature, making it a good candidate for the design of spintronic devices.

Investigation of structural, dielectric, impedance, and conductivity properties of layered perovskites type compound: LiNdSnO4

Investigation of structural, dielectric, impedance, and conductivity properties of layered perovskites type compound: LiNdSnO4

Positional Isomerism of Aromatic Heterocyclic Spacer Cations in Two-Dimensional Dion-Jacobson Hybrid Perovskites.

Ligand engineering of aromatic heterocyclic cations in two-dimensional (2D) Dion-Jacobson (DJ) perovskites has been widely explored in recent years. In this study, how the positional isomers of aromatic heterocyclic cations tune the lattice of 2D perovskites, thereby influencing the transport and recombination dynamics of charge carriers, has been investigated through nonadiabatic molecular dynamics simulations. We demonstrate that the meta-substituted 3-(aminomethyl)pyridinium (3AMPY) cations greatly reduce the strength of electron-vibration coupling since the strong hydrogen-bonding network introduced by the changes in the arrangement of spacer cations significantly suppresses the structural thermal fluctuations. Compared to the para-substituted 4-(aminomethyl)pyridinium (4AMPY) cation, using the asymmetric 3AMPY as a spacer cation can achieve improved in-plane transport performance, enhanced thermal stability, and suppressed charge carrier recombination through weakening electron-vibration interactions. Our results explain the observed lifetime difference between the two types of DJ-phase perovskites in experiments and provide new guidance for optimizing the performance of perovskite devices.

Investigation of structural, dielectric, impedance, and conductivity properties of layered perovskite type compound; NaYSnO4

In this paper, the structural study of NaYSnO4 (NYSO), a layered perovskite ceramic oxide, was done using an X-ray diffractometer (XRD) to identify the phase and determine the composition of NYSO. The microscopic structure of the sample seen by Scanning Electron Microscopy (SEM) was found to be polycrystalline and a mixture of large and small grains, which indicate the anisotropic nature of the sample. A FTIR spectroscopic behaviour of the material was used to identify the formation of different bonds in the material, and the XPS study gives an idea of the binding energy of each element in NYSO. A thorough analysis of the impedance, dielectric constant, dielectric loss, modulus and AC conductivity properties concerning temperature and frequency displays the electronic device characteristics. The complex impedance spectra were studied at temperatures range between 25 and 500˚C and frequency of 100 Hz to 1 MHz range. Nyquist plots reveal the charge conduction mechanism of the grain and well-defined grain boundaries that correspond to the resistive and capacitive phenomena of the material. Furthermore, the activation energy has been estimated to investigate the charge transportation mechanism. This article concludes by discussing future possibilities and scientific challenges in NTCR thermistors using NYSO.

Insights into the role of A/B-site substitution in chemical looping gasification of cotton stalk for enhanced syngas production over La-Co-O based perovskite oxygen carriers

Biomass chemical looping gasification (BCLG) is an emerging technology for efficient and clean utilization of cotton stalk (CS) to produce high-quality syngas. Among various oxygen carriers, perovskite oxides are holding an ever-increasing position in BCLG due to their unique structural properties and compositional flexibilities. However, research on perovskite-type oxygen carriers mostly focused on Fe-based oxides, and there is little in-depth investigation of Co-based perovskite and the role of A/B site substitution in the BCLG process. Herein, the LaCoO3 perovskite is selected as the basic oxygen carrier, and Sr, Fe are further doped on the A/B-site to form LaCo1-xFexO3 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) and La1-ySryCoO3 (y = 0, 0.2, 0.4, 0.6, 0.8) series. Effects of perovskite type, gasification temperature, steam volume fraction and oxygen carrier mass fraction of the BCLG performance are investigated. Results indicate that La0.6Sr0.4CoO3 and LaCo0.2Fe0.8O3 exhibit enhanced syngas production with the maximum of 1.304 m3/kg and 1.188 m3/kg, respectively, and outstanding cyclic stability at optimal reaction conditions. Further characterizations including H2-TPR, XPS and EPR analysis reveal that Sr substitution facilitate the formation of oxygen vacancies and adsorbed oxygen species, while Fe doping leads to the increasing concentration of oxygen vacancies and surface lattice oxygen species. Combined with the experimental and characterization results, it is deduced that the oxygen vacancies which promote the adsorption of reactants and accelerate the migration of bulk lattice oxygen, play the key role in the enhanced BCLG performance.

Carrier-phonon decoupling in perovskite thermoelectrics via entropy engineering

Thermoelectrics converting heat and electricity directly attract broad attentions. To enhance the thermoelectric figure of merit, zT, one of the key points is to decouple the carrier-phonon transport. Here, we propose an entropy engineering strategy to realize the carrier-phonon decoupling in the typical SrTiO3-based perovskite thermoelectrics. By high-entropy design, the lattice thermal conductivity could be reduced nearly to the amorphous limit, 1.25 W m−1 K−1. Simultaneously, entropy engineering can tune the Ti displacement, improving the weighted mobility to 65 cm2 V−1 s−1. Such carrier-phonon decoupling behaviors enable the greatly enhanced μW/κL of ~5.2 × 103 cm3 K J−1 V−1. The measured maximum zT of 0.24 at 488 K and the estimated zT of ~0.8 at 1173 K in (Sr0.2Ba0.2Ca0.2Pb0.2La0.2)TiO3 film are among the best of n-type thermoelectric oxides. These results reveal that the entropy engineering may be a promising strategy to decouple the carrier-phonon transport and achieve higher zT in thermoelectrics.

Preparation of Calcium Titanate Perovskite Compound, Optical and Structural Properties

In this work, we have successfully fabricated a calcium titanate perovskite compound. The resulting CaTiO3 compound was studied by preparing samples by compacting it in a powder state and using a Pousson device. The distance between the planes dhkl, Miller indices (hkl), degree of crystallinity and amorphism, structure and lattice parameters of the calcium titanate perovskite compound were determined using an X-ray diffractometer. Also, according to the results of FT-IR analysis, the formation of CaTiO3 perovskite is confirmed as a result of the study of molecular vibrations. The main broad peaks are observed in the range of 680÷400 cm-1, the absorption band at the wave number of 543,93 cm-1 corresponds to the specific stretching vibrations of Ti-O bonds and indicates the formation of the CaTiO3 perovskite type structure implies. Based on the results of these measurements, it will be possible to use semiconductor compounds in the future to create nanofilms by magnetron sputtering.

Interfacial Crosslinking for Efficient and Stable Planar TiO2 Perovskite Solar Cells.

The buried interface between the electron transport layer (ETL) and the perovskite layer plays a crucial role in enhancing the power conversion efficiency (PCE) and stability of n-i-p type perovskite solar cells (PSCs). In this study, the interface between the chemical bath deposited (CBD) titanium oxide (TiO2) ETL and the perovskite layer using multi-functional potassium trifluoromethyl sulfonate (SK) is modified. Structural and elemental analyses reveal that the trifluoromethyl sulfonate serves as a crosslinker between the TiO2 and the perovskite layer, thus improving the adhesion of the perovskite to the TiO2 ETL through strong bonding of the ─CF3 and ─SO3 - terminal groups. Furthermore, the multi-functional modifiers reduced interface defects and suppressed carrier recombination in the PSCs. Consequently, devices with a champion PCE of 25.22% and a fill factor (FF) close to 85% is achieved, marking the highest PCE and FF observed for PSCs based on CBD TiO2. The unencapsulated device maintained 81.3% of its initial PCE after operating for 1000 h.

In-Situ structural and Adsorbate Induced Surface Evolutions Monitored By Electrochemical Stress Measurements

We report on in-situ electrochemical stress measurements of well-defined surfaces during electrochemical reactions in aqueous media. Electrochemical stress measurements during hydrogen evolution reaction (HER) on Pt surfaces shows distinct pH-dependent features which we assign to anion adsorption/desorption and hydrogen adsorption/desorption. Our surface stress analysis shows higher hydrogen induced stresses at alkaline environments than stresses observed at acidic pHs. This observation is consistent with the monotonic change in apparent hydrogen binding energy with pH, most likely due to the changes in water interactions with surface. However, H-induced surface stress shows a dramatic increase around neutral pH. We will present our analysis of how interfacial water may explain this effect. Additionally, we will show how in-situ underpotential deposition of Cu on Pt and Ni on Au changes Had induced effects on these surfaces.We will also discuss the structural and compositional evolution of Sr2Fe2O6-δ thin films during oxygen evolution reaction (OER). Interestingly, in-situ electrochemical stress measurements show a tensile stress response during OER which is different from Au model surfaces. We will present our analysis of how potential controlled formation of iron (oxy)hydorxides may explain in-situ stress response and structural evolution of perovskite type structures during OER.In summary, our analysis shows how adsorbate-induced effects can be used to explain surface reactions, and particularly explain and provide insight into interfacial structural changes and water interactions at different pHs.