Triple Perovskite Research Articles

Buckled Honeycomb Lattice Compound Sr3CaOs2O9 Exhibiting Antiferromagnetism above Room Temperature

Synthesis, crystal structure and magnetic properties of a new 2:1 ordered triple perovskite Sr3CaOs2O9 are reported. The compound crystallizes in P21/c space group and features a unique buckled honeycomb lattice of osmium. It exhibits long-range antiferromagnetic ordering with a high Neel temperature of 385 K as confirmed by susceptibility, heat capacity and neutron diffraction measurements and is electrically insulating. This compound is also the first example of a 2:1 ordered osmate perovskite. Theoretical investigations indicate that Sr3CaOs2O9 features a sizeable antiferromagnetic exchange between the puckered planes resulting in a high TN. The magnetic properties of the known compound Sr3CaRu2O9 are elucidated in comparison. It shows antiferromagnetic order below TN = 200 K.

Frustration, strain and phase co-existence in the mixed valent hexagonal iridate Ba3NaIr2O9

Using detailed synchrotron diffraction, magnetization, thermodynamic and transport measurements, we investigate the relationship between the mixed valence of Ir, lattice strain and the resultant structural and magnetic ground states in the geometrically frustrated triple perovskite iridate Ba3NaIr2O9. We observe a complex interplay between lattice strain and structural phase co-existence, which is typically not observed in this family of compounds. The low temperature magnetic ground state is characterized by the absence of long-range magnetic order, and points towards the condensation of a cluster glass state from an extended regime of short range magnetic correlations.

Co-free triple perovskite La1.5Ba1.5Cu3O7±δ as a promising air electrode material for solid oxide fuel cells

La1.5Ba1.5Cu3O7±δ (LBCu) complex oxide is evaluated as a Co-free candidate air electrode material for reversible Solid Oxide Cells (rSOC). LBCu is structurally and thermomechanically compatible with La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte, maintains the layered (tripled along the c-axis) perovskite-related crystal structure at high temperatures, and shows reduced chemical expansion with the faster elongation ongoing perpendicular to the a-b plane. Its total thermal expansion is found to be moderate comparing to the Co-based perovskites. The onset temperature of the oxygen release from the material is low, ca. 300 °C in air, however, up to 800 °C the average oxidation state of copper remains above +2 in the oxidative atmospheres. The total electrical conductivity of LBCu correlates with the oxygen content, with the maximum of about 55–75 S cm−1 at ca. 350 °C in air. Functional LBCu air electrodes can be manufactured at temperatures as low as 750–800 °C, with exceptionally low (for Co-free material) polarization resistance values of 0.019 Ω cm2 at 750 °C, 0.041 Ω cm2 at 700 °C, and 0.090 Ω cm2 at 650 °C. Relatively high power output, ca. 162 mW cm−2 at 600 °C, and above 458 mW cm−2 at 750 °C is obtained for the laboratory-scale LSGM-supported cell.

Modeling and numerical simulation of high efficiency perovskite solar cell with three active layers

Recently, organic–inorganic metal halide perovskites, due to their promising optical properties, are widely used in solar cell applications yielding power conversion efficiencies (PCE) above 21%. In this study, using solar cell capacitance one-dimensional tool (SCAPS-1D), we have numerically simulated a novel solar cell consisting of three perovskite absorbers (MASnI3, MAPbI3 and FAMASnGeI3) as the active layer and achieved power conversion efficiency of 30.77%. We have also compared the performance of the proposed triple active layer perovskite solar cell (PSC) with single (MAPbI3) and double (MASnI3, MAPbI3) active layer PSCs and observed that the triple active layer PSC outperforms the single and double layer structures. Moreover, changing hole transport layer (HTL), it is found that inorganic Cu2O can be a suitable substitute for expensive prevalent organic Spiro-OMeTAD as HTL of our PSC and enhances the device PCE to 31.04%. In addition, by increasing the first absorber layer’s (MASnI3) thickness, while maintaining the total active layer thickness constant, a high PCE of 31.44% for triple active layer PSC is achieved. Furthermore, it is shown that materials with work functions more than 4.4 eV are not appropriate to be used as front contact of this structure. Finally, our simulations indicate that increase of defect density in absorber layers and working temperature of the cell monotonically degrade the efficiency of the device. We believe that the proposed triple active layer PSC can open a new route for realization of highly efficient PSCs.

Improving power conversion efficiency by Light-Assisted annealing of triple cation perovskite layer in solar cell applications

Here we propose a light-assisted annealing (LA) method, for the formation of relatively larger and uniform grains of triple perovskite crystals with less nano-cracks in a custom designed LA system with a 250 mW/cm2 halogen lamb. This method has the potential to reduce the annealing process time and energy consumption for mass production of perovskite solar cells (PSCs). For this purpose, initially, a series of perovskite films are prepared by LA method with various annealing time (1, 3, 5, 10, 15 min) to determine the optimum conditions. Subsequently, a comparative study is carried out for morphology, crystal structure and optic characterization. To assess the effect of the LA process on the structure and morphology of perovskite crystals, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and UV–Vis absorption spectroscopy techniques are carried out. Consequently, the photovoltaic application and stability tests are carried out with LA and TA films. A power conversion efficiency (PCE) of 17.86 % is achieved with an LA device annealed for 5 min (5-min-LA), while that of 16.74% is obtained with the standard device annealed on a hotplate for 60 min (60-min-TA).

Effects of temperature-dependent burn-in decay on the performance of triple cation mixed halide perovskite solar cells

The understanding of the degradation mechanisms in perovskite solar cells (PSCs) is important as they tend to degrade faster under exposure to heat and light conditions. This paper examines the temperature-dependent degradation of solution processed triple-cation mixed halide PSCs (Cs0.05(FA0.95MA0.05)0.95Pb(I0.9Br0.05)3). The PSCs were subjected to temperatures between 30 and 60 °C for 3 h (180 min) to evaluate their current–voltage performance characteristics. Temperature-induced changes in the layer and interfacial structure were also elucidated by scanning electron microscopy (SEM). Our results show that thermally induced degradation leads gradually to the burn-in decay of photocurrent density, which results in a rapid reduction in power conversion efficiency. The SEM images reveal thermally induced delamination and microvoid formation between the layers. The underlying degradation in the solar cell performance characteristics is associated with the formation of these defects (interfacial cracks and microvoids) during the controlled heating of the mixed halide perovskite cells. The electrochemical impedance spectroscopy analysis of the PSCs suggests that the device charge transport resistance and the interfacial capacitance associated with charge accumulation at the interfaces both increase with extended exposure to light.

Nanocrystalline triple perovskite compounds A3Fe2BO9(A = Sr, Ba; B = W, Te) with ferromagnetic and dielectric properties for triboelectric energy harvesting

The preparation, characterization and application of nanocrystalline Fe-based triple perovskites as layers in triboelectric nanogenerators (TENGs). TENG devices were tested for powering a calculator and charging various capacitors.

Structural distortion induced broad emission in vacancy-ordered halide triple perovskites.

Structural distortion in halide perovskites is important to tune the optical properties of the materials. The octahedra formed by metal cations and halide anions in these classes of materials remain symmetric; however, the introduction of asymmetry provides enormous opportunities to improve the photoluminescence emission and excited-state lifetimes for their application in white light emitters. In this work, we have systematically introduced asymmetry in vacancy-ordered halide triple perovskite materials Cs3M2X9 (M = Bi3+, Sb3+; X = Cl-, Br-, I-) by mixing trivalent sites in three different halide compounds. The Raman and FT-far-IR measurements were used to investigate the distortion introduced in these materials. The distortion is shown to (i) enhance self-trapped excitonic emission, which is broad and intense leading to emission in the complete visible region and (ii) improve excited-state lifetimes. This strategy to create distortion and its proven ability to improve light emission will find application in light-emitting diodes.

Analysis of performance parameters during degradation of triple-cation-based organic–inorganic hybrid perovskite solar cells

Owing to continuously growing the conversion efficiency of the organic–inorganic perovskite solar cells (PSCs) are emerging as a brilliant aspirant for high-efficiency photovoltaics (PVs). However, due to instability of the PSCs against moisture, heat, and UV radiations restricts the deployment of the PSCs for commercial application. The triple cations perovskites (T-PVT)-based PSCs are found to be more stable than the single cation-based PSCs. Moreover, inorganic electron transporting layers (ETLs) showed better stability than the organic-based ETLs against moisture. Thus, the degradation of the T-PVT layer on the Al-doped zinc oxide (AZO) ETL was studied under varying humidity. Furthermore, the influence of Al doping on the performance degradation of the AZO-ETL-based PSCs was also studied. The doping concentration of Al (RAl/Zn) in the AZO was 0%, 1%, 2%, 5%, and 10%. The overall efficiency loss (35.08%) of the degraded PSC was found to be the lowest for the AZO ETL of RAl/Zn = 5%.

Structure of triple perovskite BaSr2MgTa2O9 revisited

An experimental investigation of the structure and crystal-chemistry of the triple perovskite BaSr2MgTa2O9 is reported. Polycrystalline BaSr2MgTa2O9 was synthesized via solid-state reaction and its structure quantitatively probed at 10 and 300 ​K using neutron diffraction. Monoclinic (A2/m, a0b¯–b–) and trigonal structural models (P3¯c1, a–a–a–) were fit to diffraction data. The former was found to correctly reproduce experimental intensities, while the latter failed to do so. This difference is attributed to the ability of the monoclinic model to accurately reflect octahedral tilting. BaSr2MgTa2O9 features corner-sharing MgO6 and TaO6 octahedra with barium and strontium cations occupying cubooctahedral holes. Barium and strontium are disordered over the A site, whereas B site cations magnesium and tantalum are ordered. Chemical substitution of strontium for barium in Ba3MgTa2O9 induces tilting of MgO6 and TaO6 octahedra in two directions and geometric distortions of MgO6 octahedra.

Insight into the Role of Guanidinium and Cesium in Triple Cation Lead Halide Perovskites

The overall impact of the partial replacement (5–15%) of methylammonium (MA) in the MAPbI3 perovskite by cesium or guanidinium (Gua) cations to fabricate thin films of triple cation Cs x Gua y MA1–x–y PbI3 perovskites is studied. The structural changes are investigated by using X‐ray diffraction measurements revealing shrinkage or expansion of the unit cell upon Cs or Gua incorporation, respectively. The optoelectronic properties are characterized with photoluminescence (PL) time‐resolved spectroscopy and the space charge limited current (SCLC) method. Shorter PL time constants are obtained for the samples with only Cs, while longer PL decays are measured for the perovskites containing additional Gua cation. The SCLC measurements reveal a larger density of trap states in the Cs x MA1–x PbI3 perovskites compared to the MAPbI3 material. The PSCs fabricated with the different mixed cation Cs x Gua y MA1–x–y PbI3 perovskites reveal a good correlation with the measured optoelectronic properties. The power conversion efficiency (PCE) improves from an average value of 18.6% for the MAPbI3 to a value of 20.0% for the Cs0.05Gua0.05MA0.90PbI3 perovskite with a champion cell delivering 21.2%. On the opposite, the PCE decreases to a value of 17.3% for the double cation perovskite with Cs.

Triple perovskite structured Nd1.5Ba1.5CoFeMnO9−δ oxygen electrode materials for highly efficient and stable reversible protonic ceramic cells

The sluggish kinetics of oxygen electrode reactions represent one of the most significant barriers to realizing effective reversible protonic ceramic cells (RPCCs) at intermediate temperatures. Maximization of oxygen ion and proton conduction characteristics through hydration of electron-conducting solid oxides is a key technology that can solve this issue. We report on the exceptional performance at the oxygen electrode in RPCCs achieved using a highly defective material with excessive oxygen nonstoichiometry, Nd1.5Ba1.5CoFeMnO9−δ (NBCFM). Use of this material enables a superior reaction rate and conductivity during oxygen electrode reactions, maximizing the concentration of protons (with a high degree of hydration) as a guest ion as well as intrinsic oxygen vacancies. The peak power densities of this NBCFM cell are quite high, and a 1.4 V electrolyzing potential is achieved by NBCFM at −2.34 A‧cm−2 at 600 °C. Furthermore, these NBCFM cells are stable under prolonged (960 h) continuous operation at 600 °C.

Excess PbI2 evolution for triple-cation based perovskite solar cells with 21.9% efficiency

The triple cation mixed perovskites (CsFAMA) are known as one of the most efficient candidates for perovskite solar cells (PSCs). It is found that the power conversion efficiency (PCE) of triple-cation based devices would increase with the test time extending, and the maximum efficiency is normally obtained after several days aging storage. Here, the relationship between enhanced device performance, excess PbI2 and its evolution in triple cation perovskite films of initial days was systematically explored. The CsFAMA-PSCs are prepared by two-step methods under two environmental conditions, including in the glove box and the ambient air (30% humidity). After 7 days testing, the maximum PCE of PSCs under two conditions dramatically increased 12.4% and 12.2%, reached 21.68% and 21.89%, respectively. At initial days, the XRD peak intensities of perovskite phase gradually decreased and those corresponding to PbI2 increased. Along with time-resolved photoluminescence (TRPL) and kelvin probe force microscopy (KPFM), it was found that the defects were passivated with the evolution of PbI2. This work reveals the excess PbI2 and its evolution in perovskite film, which can further supplement the understanding of PbI2 defect passivation.

Preparation of Multifunctional Metal Oxynitride 2D Crystals and Oriented Transparent Free-Standing Oxynitride Films

Metal oxynitride two-dimensional (2D) crystals prepared by the delamination of layered compounds have attracted attention as photocatalysts, electrode catalysts, and electrolyte materials. However, the preparation of such materials is a significant challenge because of the difficulty related to producing chemically stable layered oxynitrides. In this study, oxynitride 2D crystals having triple perovskite units (A site: Ca, B site: Ta) were successfully prepared via the perfect delamination of the chemically stable Ruddlesden–Popper phase layered oxynitrides, Na2Ca2Ta3O9N. The layered compound was found to be stable during proton exchange in 6 M HNO3 and a subsequent delamination process, and the resulting oxynitride 2D crystals (herein [Ca2Ta3O9.5N0.5]−1.5) were observed to have a yellow coloration along with a band gap of 2.58 eV. The [Ca2Ta3O9.5N0.5]−1.5 2D crystals modified with RhCrOx and CoOx cocatalysts restacked with alkali ions exhibited photocatalytic activity for H2 and O2 evolution from pure water under UV light and visible light illumination. A transparent, free-standing oxynitride 2D-crystal film having a thickness of around 1 μm was prepared from the 2D-crystal suspension. This film was perfectly oriented in the [001] direction, which resulted in flexibility, mechanical strength, and airtightness due to face-to-face lamination of the 2D crystals. The proton conductivity of the oxynitride 2D-crystal film was around 10–3–10–4 S/cm at 25–50 °C (RH: 90–100%). The cell exhibited a power density of 9 mW/cm2 at 25 mA/cm2. This type of free-standing, flexible oxynitride film is expected to provide a new possibility and to enable the use of oxynitride materials in various applications.

Hydrophobic Organic Ammonium Halide Modification toward Highly Efficient and Stable CsPbI2.25Br0.75 Solar Cell

Inorganic cesium lead halide perovskite solar cells are promising candidates for next‐generation photovoltaic applications. However, their phase instability and relatively low efficiency hinder their commercialization. Herein, hydrophobic organic ammonium halides (Cl, Br, and I) are rationally used for the modification of inorganic CsPb(I0.75Br0.25)3 perovskite solar cells. Benefiting from their passivation effects and hydrophobic long alkyl chain, the modified devices exhibit enhanced efficiency and stability. Among them, the hexadecyltrimethylammonium chloride (CTAC)‐modified device shows the best performance with a power conversion efficiency (PCE) of 18.05%. Furthermore, a gradient triple anion inorganic perovskite CsPb(I0.75Br0.25)3−x Cl x layer is formed in situ during the CTAC modification, which demonstrates better phase stability than CsPb(I0.75Br0.25)3. As a result, the modified device also shows excellent stability, maintaining 94% of the initial efficiency after 35 days in N2 atmosphere.

Phase coexistence and negative thermal expansion in the triple perovskite iridate Ba3CoIr2O9

The anomalous thermal expansion in a layered $3d\text{\ensuremath{-}}5d$ based triple perovskite iridate ${\mathrm{Ba}}_{3}{\mathrm{CoIr}}_{2}{\mathrm{O}}_{9}$ is investigated using high resolution synchrotron diffraction. Below the magnetostructural transition at 107 K, the onset of antiferromagnetic order is associated with a monoclinic distortion of the hexagonal structure. Deeper within the magnetically ordered state, a part of the monoclinic phase distorts even further, and both these structural phases co-exist down to the lowest measured temperatures. We observe negative thermal expansion in this phase co-existence regime, which appears to be intimately connected to the temperature driven relative fractions of these monoclinic phases. The significant NTE observed in this system could be driven by magnetic exchange striction and is of relevance to a number of systems with pronounced spin orbit interactions.

Capacitive coupling behaviors based on triple cation organic-inorganic hybrid perovskite memristor

Memristors are new type of circuit element with the characteristics of both integrated computing and storage, which can promote the development of artificial intelligence and memory- computing fusion technology. In this manuscript, a novel triple cation Organic-inorganic hybrid perovskite (OHP) based optoelectronic coupling memristors with structure of FTO/TiO2/Cs0.05(FAxMA1−x)0.95PbBryI3−y/Al were fabricated, hysteresis loops with low power consumption, high HRS/LRS ratio and obvious light response are presented. Besides, capacitive coupling behaviors are observed in current curves. By changing voltage or light condition, memristors can evolve from capacitive behavior to pure memristive behavior. Physical mechanisms are discussed to explain this phenomenon. This work opens up a way in improving the resistive switching performances of OHP memristors, and can be of great benefit to the potential application in neuromorphological analysis.

Effect of reaction time on the morphology and efficiency of ambient-air-processed CsFAMAPbIBr triple cation-mixed perovskite solar cells

The mixed-cation halide perovskites containing formamidinium (FA) are vulnerable to moisture due to easy bonding of FA moieties with H2O. Thus, a strict humidity controlled environment is indispensable for the highest efficiency CsFAMAPbIBr perovskites synthesis, which hinders the development of perovskite manufacturing in ambient atmosphere. In addition, the morphological evolution of CsFAMAPbIBr perovskites in a humid environment and consequent photovoltaic performance is important for understanding ambient air processed mixed perovskite solar cells, but few have been reported. Here, CsFAMAPbIBr perovskites were synthesized in an ambient air atmosphere by a sequential two-step deposition method. The effect of the reaction time is focused to corelate morphological variation and the resultant photovoltaic properties. Using the optimal reaction time of 5 s, CsFAMAPbIBr based planar solar cells with a power conversion efficiency (PCE) of 16.01% were achieved.

Impedance spectroscopy study of electrical response and correlation with structural properties in the La2SrFe2CoO9 triple complex perovskite

The triple perovskite with formula La2SrFe2CoO9 has been synthesized and experimentally studied. The samples were obtained by the solid-state reaction method. Scanning Electron Microscopy images show a strongly diffused granular surface morphology with mean grain size of 1 μm and Electron Dispersive X-ray spectra evidence that the chemical composition of sample is in good agreement with the nominal values of the stoichiometric formula. The electrical transfer functions were studied through the Impedance Spectroscopy technique in the range from 1 mHz to 100 KHz and in the temperature, range from 75 to 295 K. The interpretation of BODE and NYQUIST - diagrams allows the development of an equivalent circuit which explain the behavior of the electrical response throughout the frequency range. The conductance measurements showed the dependence of the conduction mechanisms with frequency and temperature. Structural and impedance properties are correlated allowing to propose mechanisms of charge transfer.

Evolution of the structural, magnetic, and electronic properties of the triple perovskite Ba3CoIr2O9

We report a comprehensive investigation of the triple perovskite iridate Ba$_{3}$CoIr$_{2}$O$_{9}$. Stabilizing in the hexagonal $P6_{3}/mmc$ symmetry at room temperature, this system transforms to a monoclinic $C2/c$ symmetry at the magnetic phase transition. On further reduction in temperature, the system partially distorts to an even lower symmetry ($P2/c$), with both these structurally disparate phases coexisting down to the lowest measured temperatures. The magnetic structure as determined from neutron diffraction data indicates a weakly canted antiferromagnetic structure, which is also supported by first-principles calculations. Theory indicates that the Ir$^{5+}$ carries a finite magnetic moment, which is also consistent with the neutron data. This suggests that the putative $J=0$ state is avoided. Measurements of heat capacity, electrical resistance noise and dielectric susceptibility all point towards the stabilization of a highly correlated ground state in the Ba$_{3}$CoIr$_{2}$O$_{9}$ system.