Perovskite Structure Research Articles

Bulk Photovoltaic Effect Induced by Non-Covalent Interactions in Bilayered Hybrid Perovskite for Efficient Passive X-Ray Detection.

Hydrogen bonding as a multifunctional tool has always influenced the structure of hybrid perovskites. Compared with the research on hydrogen bonding, the study of halogen-halogen interactions on the structure and properties of hybrid perovskites is still in its early stages. Herein, a polar bilayered hybrid perovskite (IEA)2FAPb2I7 (IEA+ is 2-iodoethyl-1-ammonium, FA is formamidinium) with iodine-substituted spacer is successfully constructed by changing the configuration of interlayer cations and regulating non-covalent interactions at the organic-inorganic interface, which shows a shorter interlayer spacing and higher density (ρ = 3.862gcm-3). The generation of structure polarity in (IEA)2FAPb2I7 is caused by the synergistic effect of hydrogen bonding and halogen-halogen interactions. Especially, as the length of the carbon chain in organic cations decreases, the I---I interaction in the system gradually strengthens, which may be the main reason for the symmetry-breaking. Polarity-induced bulk photovoltaics (Voc = 1.0V) and higher density endow the device based on (I-EA)2FAPb2I7 exhibit a high sensitivity of 175.6µCGy-1cm-2 and an ultralow detection limit of 60.4nGys-1 at 0V bias under X-ray irradiation. The results present a facile approach for designing polar multifunctional hybrid perovskites, also providing useful assistance for future research on halogen-halogen interactions.

2D Perovskite Nanosheet‐Driven Polymeric Nanocomposites as Gate Dielectrics for Flexible Negative‐Capacitance Applications

AbstractDesigning composite gate dielectrics tailored by incorporating inorganic perovskite nanofillers into a polymer matrix to develop flexible low‐voltage transistors can be challenging because homogeneous dispersion of nanomaterials in the matrix is difficult to achieve; thus, degradation of the electrically insulating properties of nanocomposite layers is often observed. In this study, nanocomposite dielectrics are presented that consist of 2D Ba5Ta4O15 nanosheets (BTO NSs) for the first time. Perovskite BTO is introduced using the Langmuir–Blodgett method to construct a precise and pinhole‐free interface for the homogeneous assembly of 2D nanosheets. Its high k value and ferroelectric properties, which arise from the perovskite structure, can be harnessed to achieve attractive polarization and remarkable electronic properties. The 2D BTO NSs can also be utilized as phase crystallization fillers to enhance the ferroelectric properties of polyvinylidene fluoride (PVDF). Additionally, the multilayer PVDF/perovskite nanosheet hybrid dielectric, which reaches an unprecedentedly high dielectric constant of 22.4, exhibits effective dielectric relaxation related to the interfacial induced ferroelectric polarization and decisive negative‐capacitance response.

Effects of La-N Co-Doping of BaTiO3 on Its Electron-Optical Properties for Photocatalysis: A DFT Study

In cation–anion co-doping, rare earth elements excel at regulating the electronic structure of perovskites, leading to their improved photocatalytic performance. In this regard, the impact of co-doping rare earth elements at the Ba and Ti sites in BaTiO3 on its electronic and photocatalytic properties was thoroughly investigated based on 2 × 2 × 2 supercell structures of BaTiO3 with different La concentrations of 12.5% and 25% using DFT calculations. The band structure, density of states, charge density difference, optical properties, and the redox band edge of the co-doped models mentioned above were analyzed. The results indicated that the BaTiO3 structure co-doped with 25% La at the Ti site exhibited higher absorption in the visible range and displayed a remarkable photocatalytic water-splitting performance. The introduced La dopant at the Ti site effectively reduced the energy required for electronic transitions by introducing intermediate energy levels within the bandgap. Our calculations and findings of this study provide theoretical support and reliable predictions for the exploration of BaTiO3 perovskites with superior photocatalytic performances.

Contribution of (Bi0.45Y0.05)Na0.5ZrO3 to induced multiphase coexistence and enhanced piezoelectric properties of K0.5Na0.5NbO3 lead-free ceramics

In this study, new lead-free piezoelectric ceramics (1 − x)(K0.5Na0.5)NbO3 (KNN)–x(Bi0.45Y0.05)Na0.5ZrO3 (BYNZ) were prepared using the conventional solid-state method, and the relation between the doping amount of (Bi0.45Y0.05)Na0.5ZrO3 and its structural and electrical properties was investigated. Material characterization and structural analyses conducted using X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy revealed that KNN–BYNZ ceramics formed single perovskite structures at 0 ≤ x ≤ 0.05 and a polycrystalline phase boundary (PPB) for the coexisting orthorhombic and tetragonal phases at 0.03 ≤ x ≤ 0.05. The ceramics exhibited desirable electrical properties at x = 0.04 (d33 = 305 pC/N, kp = 45.8 %, εr = 1316, tanδ = 2.4 %, Tc = 332 °C, Pr = 28.2 μC/cm2, and Ec = 1.07 kV/mm). These findings reveal that the introduction of BYNZ enables the effective formation of a PPB in the KNN-based ceramics to improve their electrical properties, and they exhibit potential for replacing lead-based piezoelectric ceramics in the market.

Dielectric Engineering of Perovskite BaMnO3 for the Rapid Heterogeneous Nucleation of Pt Nanoparticles for Catalytic Applications

AbstractMicrowave heating provides a rapid method for the heterogeneous nucleation of noble metal particles on perovskite support materials for electrocatalytic purposes. To succeed, dielectric tuning of perovskite materials becomes fundamental. Herein, the dielectric engineering of the BaMnO3 perovskite system is carried out through the use of B‐site doping to give BaTi0.5Mn0.5O3. Using a combination of atomic‐scale imaging and electron energy loss spectroscopy (EELS), the preferential filling of the M1 and M3 B‐sites with Mn and Ti ions in the 12R‐rhombohedral perovskite structure is established. While the addition of Ti in the BaMnO3 system has no detrimental effects on the presence of the oxygen reduction reaction (ORR) active Mn3+ states at the surface, it does alter the dielectric constant and loss tangent, thus facilitating the heterogeneous nucleation of Pt nanoparticles on BaTi0.5Mn0.5O3 via rapid microwave heating. Higher Pt loading regimes are found to increase the size and aggregation of the nucleated particles, thus reducing their ORR activity. Therefore, lower Pt loading not only reduces costs but improves overall activity. This work represents future possibilities for the dielectric engineering of perovskite and similar support materials to aid in the quick and easy formation of stable noble metal‐support catalytic systems.

Machine learning-enabled chemical space exploration of all-inorganic perovskites for photovoltaics

The vast compositional and configurational spaces of multi-element metal halide perovskites (MHPs) result in significant challenges when designing MHPs with promising stability and optoelectronic properties. In this paper, we propose a framework for the design of B-site-alloyed ABX3 MHPs by combining density functional theory (DFT) and machine learning (ML). We performed generalized gradient approximation with Perdew–Burke–Ernzerhof functional for solids (PBEsol) on 3,159 B-site-alloyed perovskite structures using a compositional step of 1/4. Crystal graph convolution neural networks (CGCNNs) were trained on the 3159 DFT datasets to predict the decomposition energy, bandgap, and types of bandgaps. The trained CGCNN models were used to explore the compositional and configurational spaces of 41,400 B-site-alloyed ABX3 MHPs with a compositional step of 1/16, by accessing all possible configurations for each composition. The electronic band structures of the selected compounds were calculated using the hybrid functional (PBE0). Then, we calculated the optical absorption spectra and spectroscopic limited maximum efficiency of the selected compounds. Based on the DFT/ML-combined screening, 10 promising compounds with optimal bandgaps were selected, and from among these 10 compounds, CsGe0.3125Sn0.6875I3 and CsGe0.0625Pb0.3125Sn0.625Br3 were suggested as photon absorbers for single-junction and tandem solar cells, respectively. The design framework presented herein is a good starting point for the design of mixed MHPs for optoelectronic applications.

Optimization of the performance of CsPbI2Br perovskite solar cells in air by adding polyethylene-graft-maleic anhydride and its mechanism

In this study, by adding Polyethylene-graft-maleic anhydride (PGMA) to the inorganic CsPbI2Br perovskite film, the coordination bonds and hydrogen bonds between PGMA and CsPbI2Br cooperate to passivate defects, regulate energy level and stabilize the perovskite structure and eventually improve the device performance. We systematically study the effects of PGMA addition on the morphology, structure, light absorption, defect concentration and carrier lifetime, hydrophobicity, and optical stability and room temperature black phase stability of CsPbI2Br films, and the photoelectric performance and air stability of PSCs, as well as their mechanism. The experimental results show that the addition of 3 wt% of PGMA greatly improves the photoelectric conversion efficiency (PCE) of CsPbI2Br PSCs by 40.19 % because of the synergistic passivation effects and energy level tuning. The hydrogen bonds between –CH2 in PGMA and I−/Br− in CsPbI2Br, along with the coordination of carbonyl groups with Cs+/Pb2+, improve carrier transport and collection by inactivating flaw and managing the level, reducing the non-radiative recombination losses. In addition, the PSCs with 3 wt% of PGMA maintain 80 % of their initial efficiency even after 600 h in high humidity air environment due to the synergistic effect of coordination bonds and hydrogen bonds. Our study provides valuable insights into the use of PGMA to improve the performance of all-inorganic CsPbI2Br PSCs and the practicality of perovskite solar cells.

K- and Na-rich davemaoite inclusion in diamond is not inherited from deeply subducted oceanic crusts

Deep potassium (K) and sodium (Na) cycles can affect the physiochemical properties and geodynamic processes of the Earth's interior, to some extent. Recently reported natural K- and Na-rich davemaoite inclusion in superdeep diamond (Tschauner et al., 2021), which is still controversial (Walter et al. 2022a; Tschauner et al., 2022), motivated us to reinvestigate the recycling and partitioning behaviours of K and Na in the subducting oceanic crust under deep-mantle P-T conditions. In this study, we experimentally determined the partitioning of Na and K, as well as other major elements, in a natural phengite-rich eclogite system under 5–30 GPa and 850–1550 °C, relevant to P-T conditions from the deep upper mantle to the uppermost lower mantle. We found that the produced davemaoite with the perovskite structure contained minimal amounts of other elements, including K and Na. Therefore, we conclude that K- and Na-rich davemaoite inclusion in the superdeep diamond cannot be inherited from deeply subducted oceanic crusts. In addition, our experimental results further support previous arguments overestimating the K and Na, and other elemental contents in natural davemaoite, which may further indicate that the reported diamond “inclusion” with abnormally high heteroatoms (Tschauner et al., 2021) is not a davemaoite from the lower mantle (Walter et al. 2022a). Finally, we combined the high-pressure phase relationship in the upper continental crust, oceanic basalt, and pyrolite systems from previous studies, and constructed a geodynamical model for the deep K and Na cycles along with the subduction of the oceanic slabs into the uppermost lower mantle.

Gas Sensors Based on Semiconductor Metal Oxides Fabricated by Electrospinning: A Review

Electrospinning has revolutionized the field of semiconductor metal oxide (SMO) gas sensors, which are pivotal for gas detection. SMOs are known for their high sensitivity, rapid responsiveness, and exceptional selectivity towards various types of gases. When synthesized via electrospinning, they gain unmatched advantages. These include high porosity, large specific surface areas, adjustable morphologies and compositions, and diverse structural designs, improving gas-sensing performance. This review explores the application of variously structured and composed SMOs prepared by electrospinning in gas sensors. It highlights strategies to augment gas-sensing performance, such as noble metal modification and doping with transition metals, rare earth elements, and metal cations, all contributing to heightened sensitivity and selectivity. We also look at the fabrication of composite SMOs with polymers or carbon nanofibers, which addresses the challenge of high operating temperatures. Furthermore, this review discusses the advantages of hierarchical and core-shell structures. The use of spinel and perovskite structures is also explored for their unique chemical compositions and crystal structure. These structures are useful for high sensitivity and selectivity towards specific gases. These methodologies emphasize the critical role of innovative material integration and structural design in achieving high-performance gas sensors, pointing toward future research directions in this rapidly evolving field.

Emission behaviors from ZnO microwire pumped CsPbBr3 perovskite microwire.

Perovskite semiconductor materials have attracted significant attention in the fields of photovoltaics and luminescence due to their excellent photoelectric properties, such as high carrier mobility, high absorption coefficient, and high fluorescence quantum yield. In particular, low-dimensional metal-halide perovskite microcrystalline materials have been reported to exhibit low-dimensional lasing phenomena and laser devices due to their high gain and widely tunable bandgap. In this Letter, one-dimensional (1-D) ZnO microwires with their ultraviolet lasing emissions are utilized as an excitation source to pump CsPbBr3 microwire on hybrid ZnO-CsPbBr3 microscale structures. At higher excitation, the amplified spontaneous emission (ASE) behaviors from CsPbBr3 microwire are realized with ultralow threshold by indirect pumping from the ZnO lasing emission for the first time, to the best of our knowledge. In comparison, the ASE behaviors from the CsPbBr3 microwire directly pumped by Nd:YAG Q-switched laser and continuous wave laser are also performed at room temperature. There are also no multimode lasing behaviors observed. The paper provides a new method to achieve a low threshold on-chip microlaser by a high-quality perovskite micro-nano structure.

Perovskite photovoltaic effect and its application on solar cell

Perovskite photovoltaic effect and its application on solar cell

Nano‐LaMnO3 Modified Separator for Enhanced Redox Reaction Kinetics and Electrochemical Performance of Lithium‐Sulfur Batteries

AbstractThe “shuttle effect” and sluggish conversion reaction kinetics of polysulfides seriously hinder the practical application of Li−S batteries. In this study, nano‐sized LaMnO3 (N‐LMO) with typical perovskite structure combined with highly‐conductive carbon black (SP) was introduced on the commercial separator to fabricate a functional surface modification. It is found that the polar N‐LMO with abundant active sites offers strong chemisorption towards the soluble polysulfides meanwhile accelerates their redox conversion, and the conductive SP contributes to extra spots to reactivate the trapped sulfur species. Consequently, the synergistic effect of adsorption‐catalysis‐conduction built by the cooperative N‐LMO/SP modification greatly enhances the sulfur redox kinetics as well as suppresses the polysulfide shuttling not at the expense of weakening Li‐ion transport, which endows the Li−S cell with a high initial discharge capacity of 1143.6 mAh g−1 at 0.2 C and a capacity decay rate of only 0.072 % per cycle at 1 C over 500 cycles.

Electron Spectroscopy and Microscopy: A Window into the Surface Electronic Properties of Polycrystalline Metal Halide Perovskites.

In the past years, an increasing number of experimental techniques have emerged to address the need to unveil the chemical, structural, and electronic properties of perovskite thin films with high vertical and lateral spatial resolutions. One of these is angle-resolved photoemission electron spectroscopy which can provide direct access to the electronic band structure of perovskites, with the aim of overcoming elusive and controversial information due to the complex data interpretation of purely optical spectroscopic techniques. This perspective looks at the information that can be gleaned from the direct measurement of the electronic band structure of single crystal perovskites and the challenges that remain to beovercame to extend this technique to heterogeneous polycrystalline metal halide perovskites.

Modulation and Enhancement of Red Luminescence in Ca2GdSbO6: Eu3+ Phosphor by Co-Doping with Bi3.

The double perovskite structure of Ca2GdSbO6 as a fluorescent phosphor matrix material possesses a stable structure, making it an excellent candidate for a matrix material. In this study, single-doped Ca2GdSbO6: Eu3+ fluorescent phosphors and Bi3+ sensitized Ca2GdSbO6: Eu3+, Bi3+ fluorescent phosphor materials were synthesized using the high-temperature solid-state method. The luminescence of this phosphor is based on the 5D0→4F2 transition emission of Eu3+ ions, which occurs at 612nm. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectra, high-temperature fluorescence spectra, and fluorescence decay lifetimes to study the phase structure, optical properties, crystal structure, and chemical purity of the samples. The performance of the single-doped phosphor was significantly improved by the addition of Bi3+ sensitizer. The luminescence intensity increased by nearly 100% compared to Ca2GdSbO6: Eu3+ phosphor, with a quantum efficiency increase of 124%. The thermal quenching activation energy was found to be 0.299eV, and the luminescence intensity remained at 70.3% of room temperature at 453K. These results indicate that the co-doping of Bi3+ has a modulation and enhancement effect on the luminescence of Ca2GdSbO6: Eu3+ red phosphor, showing great potential for application in near-ultraviolet-excited white LED devices.

Exploring the Influence of Cation and Halide Substitution in the Structure and Optical Properties of CH3NH3NiCl3 Perovskite.

This manuscript details a comprehensive investigation into the synthesis, structural characterization, thermal stability, and optical properties of nickel-containing hybrid perovskites, namely CH3NH3NiCl3, CsNiCl3, and CH3NH3NiBrCl2. The focal point of this study is to unravel the intricate crystal structures, thermal behaviors, and optical characteristics of these materials, thereby elucidating their potential application in energy conversion and storage technologies. X-ray powder diffraction measurements confirm that CH3NH3NiCl3 adopts a crystal structure within the Cmcm space group, while CsNiCl3 is organized in the P63/mmc space group, as reported previously. Such structural diversity underscores the complex nature of these perovskites and their potential for tailored applications. Thermal analysis further reveals the stability of CH3NH3NiCl3 and CH3NH3NiBrCl2, which begin to decompose at 260 °C and 295 °C, respectively. The optical absorption properties of these perovskites studied by UV-VIS-NIR spectroscopy revealed the bands characteristic of Ni2+ ions in an octahedral environment. Notably, these absorption bands exhibit subtle shifts upon bromide substitution, suggesting that optical properties can be finely tuned through halide modification. Such tunability is paramount for the design and development of materials with specific optical requirements. By offering a detailed examination of these properties, the study lays the groundwork for future advancements in material science, particularly in the development of innovative materials for sustainable energy technologies.

In situ fabrication of porous polymer films embedded with perovskite nanocrystals for flexible superhydrophobic piezoresistive sensors

The application of pressure sensors based on perovskite in high-humidity environments is limited by the effect of water on their stability. Endowing sensors with superhydrophobicity is an effective strategy to overcome the issue. In this work, MAPbBr3/Polyvinylidene Fluoride-TFSI composite was prepared by a one-step in-situ strategy to form a flexible superhydrophobic pressure sensor, which exhibited a contact angle of 150.25°. The obtained sensor exhibited a sensitivity of 0.916 in 1 kPa, a detection limit of 0.2 Pa, a precision of 0.1 Pa, and a response/recovery of ∼100 ms, along with good thermal stability. Through density functional theory calculations, it is revealed that the formation of the porosity is attributed to the interaction between the polymer and EMIM TFSI, which further leads to superhydrophobicity. And, the perovskite structure is easy to change under pressure, affecting the carrier transport and electrical signals output, which explains the sensing mechanism. In addition, the sensor performed well in monitoring facial expression, pulse, respiration, finger bending, and wind speed ranging from 1 m/s to 6 m/s. With both the Linear Regression and the Random Forest algorithm, the sensor can monitor the wind speed with an R2 greater than 0.977 in 60 tests.

Novel room-temperature synthesis of pioneering CsPbX3@(Ce)UiO-66-Y hybrid nanomaterials for boosted photocatalytic hydrogen evolution

Perovskites are attractive structures for photocatalytic hydrogen generation, but also are limited by low stability, which can be improved by combination with other materials. Perovskite structures have potential for photocatalytic hydrogen generation; however, their practical application is hindered by inherent low stability. This limitation can be effectively mitigated through strategic combinations with complementary materials. Therefore, hybrids consisting of the perovskite CsPbX3 (X = Br, I) and the metal–organic framework (Ce)UiO-66-Y (Y = H, Br, NH2) were successfully synthesized for the first time, using a straightforward ligand-assisted reprecipitation synthesis at room temperature. To develop a room temperature synthesis for CsPbX3@(Ce)UiO-66-Y hybrid nanomaterials, herein, we optimized the synthesis of perovskite firstly (considering factors such as the choice of solvents, the drying of stabilizers, and the purification) and then developed an efficient way to combine both materials. Six types of hybrid materials, differing in the type of perovskite and functional group in the MOFs linker, were synthesized by the introduction of MOFs powder into a solution containing perovskite precursors (CsX and PbX2 in DMF stabilized by oleyamine and oleic acid) followed by antisolvent addition. We demonstrated that the hybrids containing perovskite in combination with MOF (Ce)UiO-66-NH2 in a molar ratio of 13:1 exhibited significantly higher activity and twice as long reaction stability time compared to the individual components of the hybrids when tested separately. This outcome underscores the presence of a synergistic effect, highlighting the potential of these hybrid materials in catalyzing hydrogen generation.

Effect of Dual-Organic Cations on the Structure and Properties of 2D Hybrid Perovskites as Scintillators.

Two-dimensional (2D) hybrid organic-inorganic perovskite (HOIP) crystals show promise as scintillating materials for wide-energy radiation detection, outperforming their three-dimensional counterparts. In this study, we synthesized single crystals of (PEA2-xBZAx)PbBr4 (x ranging from 0.1 to 2), utilizing phenethylammonium (C6H5CH2CH2NH3+) and benzylammonium (C6H5CH2NH3+) cations. These materials exhibit favorable optical and scintillation properties, rendering them suitable for high light yield (LY) and fast-response scintillators. Our investigation, employing various techniques such as X-ray diffraction (XRD), photoluminescence (PL), time-resolved (TR) PL, Raman spectroscopy, radioluminescence (RL), thermoluminescence (TL), and scintillation measurements, unveiled lattice strain induced by dual-organic cations in powder X-ray diffraction. Density functional theory analysis demonstrated a maximal 0.13 eV increase in the band gap with the addition of BZA cation addition. Notably, the largest Stokes shift of 0.06 eV was observed in (BZA)2PbBr4. The dual-organic cation crystals displayed >80% fast component scintillation decay time, which is advantageous for the scintillating process. Furthermore, we observed a dual-organic cations-induced enhancement of electron-hole transfer efficiency by up to 60%, with a contribution of >70% to the fast component of scintillation decay. The crystal with the lowest BZA concentration, (PEA1.9BZA0.1)PbBr4, demonstrated the highest LYs of 14.9 ± 1.5 ph/keV at room temperature. Despite a 55-70% decrease in LY for BZA concentrations >5%, simultaneous reductions in scintillation decay time (12-32%) may work for time-of-flight positron emission tomography and photon-counting computed tomography. Our work underscores the crucial role of dual-organic cations in advancing our understanding of 2D-HOIP crystals for materials science and radiation detection applications.

Integrated study of the structural and magnetic characteristics of Nd(Mn, Cr)0.5O3: exploring perovskite material

In this work, a perovskite material, Nd(Mn,Cr)0.5O3, is synthesized by a sol–gel chemical route method, and the structural and magnetic properties of the prepared samples were studied for a range of annealing temperatures. The variation of structural parameters against annealing temperatures is analyzed via Rietveld refinement, and it exhibits orthorhombic cubic geometry with non-monotonically increasing lattice parameters. lattice strain is due to canting in the Cr3+ and Mn3+ ions and the presence of strain is also confirmed by the shifting of XRD peaks towards a higher 2θ angle. The obtained Goldschmidt tolerance factor is 0.87, which confirms the stability of the perovskite structure. The magnetic properties of the prepared samples show the ferromagnetic transition temperature ranging from 86.5 K to 82.2 K due to super-exchange interaction between Cr3+ and Mn3+ ions via oxygen ions. The stability in crystal structure, lower value of strain, and ferromagnetic nature at low temperature for the samples annealed up to1000 °C may make this material applicable for magnetic data storage.

Enhanced dielectric and relaxation properties in Sm3+ doped KNNT ceramics

The effect of Sm3+ doping on KNNT ceramic were comprehensively investigated, specifically focusing on the phase, microstructure, and dielectric properties of (1-x)K0.5Na0.5Nb0.7Ta0.3O3·xSm2O3(x=0-1.6%)(denoted KNNT–xSm) ceramics. All ceramics have the perovskite structure, and doping with Sm3+ refined the ceramic grains, resulting in an increase in the room-temperature dielectric permittivity from 998 to 1568 at 100kHz. In addition, the dielectric loss (tanδ) reduced from 0.026 to 0.019, relaxation diffusion coefficient(γ) increased from 1.35 to 1.88, and the activation energy(Ea) was 0.9–1.08eV. Thus, the dielectric and relaxation properties of KNNT ceramic can be significantly improved by Sm3+ doping.