Two-dimensional (2D) molybdenum disulfide (MoS2) has shown considerable potential for photodetection, yet existing MoS2-based photodetectors require either external voltage bias or complex heterojunctions. In this work, we present a new device concept based on flexoelectric engineering of bulk photovoltaic effect (BPVE) of 2Hu2014MoS2, simplifying the device configuration considerably while enhancing its self-powered photodetection performance. By introducing a strain gradient in the suspended 2Hu2014MoS2, we break its inversion symmetry, resulting in BPVE in the otherwise centrosymmetric system. The significant flexoelectric polarization induced also facilitates efficient photocarrier separation, leading to a 41-fold enhancement in short-circuit photocurrent under a strain gradient of 0.95. Furthermore, the flexoelectric-engineered photodetector can be dynamically tuned via air pressure, enabling multilevel photoconductance and achieving a responsivity of 191 mA/W. This performance surpasses existing self-powered MoS2-based photodetectors reported in literature, offering a strategy for enhanced photodetection.

Optoelectronic logic gates (OELGs) converting photonic inputs into electric output based on Boolean logic are promising for next-generation computations, and it is highly desirable to be able to control the current polarity by light for multifunctional devices. Here we report a new strategy for OELGs based on bipolar photoconduction intrinsic to ferroelectric materials, simplifying the device configuration considerably while enabling multiple logic operations. We demonstrate this concept in two-dimensional (2D) ferroelectric CuInP2S6 (CIPS), taking advantage of the fact that its polarization switching is intimately coupled with Cu cation migration, and thus can be deterministically driven by both above- and below-bandgap illumination via the photothermal effect. This in turn switches the polarity of the photocurrent arising from the bulk photovoltaic effect (BPVE), which is sensitive to the light intensity, enabling the execution of "OR", "XOR", and "NOT" logic operations in a single device with a simple sandwich structure.

Two-dimensional (2D) molybdenum disulfide (MoS2) has shown considerable potential for photo-detection, yet existing MoS2-based photodetectors require either external voltage bias or complex heterojunctions. In this work, we present a new device concept based on flexoelectric engineering of bulk photovoltaic effect (BPVE) of 2H-MoS2, simplifying the device configuration considerably while enhancing its self-powered photodetection performance. By introducing a strain gradient in the suspended 2H-MoS2, we break its inversion symmetry, resulting in BPVE in the otherwise centrosymmetric system. The significant flexoelectric polarization induced also facilitates efficient photocarrier separation, leading to a 41-fold enhancement in short-circuit photocurrent under a strain gradient of 0:95 mu m-1. Furthermore, the flexoelectric-engineered photodetector can be dynamically tuned via air pressure, enabling multilevel photoconductance and achieving a responsivity of 191 mA/W. This performance surpasses existing self-powered MoS2-based photodetectors reported in literature, offering a strategy for enhanced photodetection. (c) 2025 The Authors. Published by Elsevier B.V. on behalf of The Chinese Ceramic Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The bulk photovoltaic effect (BPVE) offers an interesting approach to generate a steady photocurrent in a single-phase material under homogeneous illumination, and it has been extensively investigated in ferroelectrics exhibiting spontaneous polarization that breaks inversion symmetry. Flexoelectricity breaks inversion symmetry via a strain gradient in the otherwise nonpolar materials, enabling manipulation of ferroelectric order without an electric field. Combining these two effects, we demonstrate active mechanical control of BPVE in suspended 2-dimensional CuInP2S6 (CIPS) that is ferroelectric yet sensitive to electric field, which enables practical photodetection with an order of magnitude enhancement in performance. The suspended CIPS exhibits a 20-fold increase in photocurrent, which can be continuously modulated by either mechanical force or light polarization. The flexoelectrically engineered photodetection device, activated by air pressure and without any optimization, possesses a responsivity of 2.45 x 10(-2) A/W and a detectivity of 1.73 x 10(11) jones, which are superior to those of ferroelectric-based photodetection and comparable to those of the commercial Si photodiode.

The relaxor ferroelectric material (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) has attracted great attention due to its excellent electrical properties. High quality Mn-Sm co-doped 0.68PMN-0.32PT thin films were fabricated on the Pt/Ti/SiO2/Si substrates with less oxygen vacancies by using sol-gel based spin coating method. It was found that 2 mol%Sm-1 mol%Mn doped PMN-PT thin films possess high dielectric permittivity (εr ~ 1895.24) and relatively low dielectric loss (tanδ ~ 0.039) at 1 kHz, and superior ferroelectric polarization (Pmax ~ 53.71 μC/cm2, Pr ~ 30.85 μC/cm2) with high dielectric breakdown strength (~ 1586.70 kV/cm), mainly due to its low leakage current density (~ 10-7 A/cm2). This work suggest an effective approach to improve the dielectric, piezoelectric and ferroelectric properties of PMN-PT thin films based on co-doping.

Abstract Bulk photovoltaic effect (BPVE) offers an interesting approach to generate a steady photocurrent in a single-phase material under homogeneous illumination, and it has been extensively investigated in ferroelectrics exhibiting spontaneous polarization that breaks inversion symmetry. Flexoelectricity breaks inversion symmetry via strain gradient in the otherwise nonpolar materials, enabling manipulation of ferroelectric order in the absence of electric field. Combining these two effects together, we demonstrate active mechanical control of BPVE in suspended 2-dimensional CuInP2S6 (CIPS) that is ferroelectric yet sensitive to electric field, which enables practical photodetection devices with order of magnitude enhancement in performance. It is found that the suspended CIPS exhibits 20-fold increase in photocurrent, which can be continuously modulated by either mechanical force or light polarization angle. The flexoelectrically engineered photodetection device, activated by air pressure and without any optimization, possesses a responsivity of (2.45 x 10-2) A/W and a detectivity of (1.73 x 1011) Jones, which are superior to ferroelectric-based photodetection and comparable to the commercial Si photodiode.

The high-quality (0.78-x)BiTi0. 1Fe0.8Mg0. 1O3- 0.22CaTiO3-(x)Na0.5Bi0.5TiO3 nanoscale-thick thin films were prepared successfully on the Pt/Ti/SiO2/Si substrate via the sol-gel method. The influence of Na0.5Bi0.5TiO3 doping on the structure, topography, piezoelectricity, ferroelectricity, and dielec-tricity of BTFM-CTO-NBT thin films was investigated systemati-cally. The X-ray diffraction and Raman results manifested that NBT doping induced the formation of the tetragonal phase, which existed between the rhombohedral and orthorhombic phases, and the elemental mappings revealed that the distribution of each element was uniform simultaneously. X-ray photoelectron spec-troscopy analysis showed that NBT doping could effectively restrain the reduction of Fe3+, thereby reducing the oxygen vacancy concentration. The film had a minimum leakage current of about 3.19 x 10-10 A/cm2, a higher piezoelectric response, a maximum remnant polarization (2Pr = 174.64 mu C/cm2), and a relatively smaller coercive field (Ec = 359.90 kV/cm) as x = 0.05. At the same time, the corresponding film had a maximum dielectric constant (469.6) and a minimum dielectric loss (0.063) at 1 kHz. These insights offer an alternative pathway to enhance the properties of BTFM-CTO thin films.

The hexagonal rare earth ferrites h-RFeO3(R = rare earth element) have been recognized as promising candidates for a room-temperature multiferroic system, and the primary issue for these materials is how to get a stable hexagonal structure since the centrosymmetric orthorhombic structure is generally stable for most RFeO3 at room-temperature, while the hexagonal phase is only stable under some strict conditions. In the present work, h-Lu1-xInxFeO3 (x = 0-1) thin films were prepared on a Nb-SrTiO3 (111) single-crystal substrate by a pulsed laser deposition (PLD) process, and the multiferroic characterization was performed at room temperature. With the combined effects of chemical pressure and epitaxial strain, the stable hexagonal structure was achieved in a wide composition range (x = 0.5-0.7), and the results of XRD (X-ray diffraction) and SAED (selected area electron diffraction) indicate the super-cell match relations between the h-Lu0.3In0.7FeO3 thin film and substrate. The saturated P-E hysteresis loop was obtained at room temperature with a remanent polarization of about 4.3 μC/cm2, and polarization switching was also confirmed by PFM measurement. Furthermore, a strong magnetoelectric coupling with a linear magnetoelectric coefficient of 1.9 V/cm Oe was determined, which was about three orders of magnitude larger than that of h-RFeO3 ceramics. The present results indicate that the h-Lu1-xInxFeO3 thin films are expected to have great application potential for magnetoelectric memory and detection devices.

Triple-cation mixed-halide perovskite Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3 (CsFAMA) has emerged as one of the most promising candidates for future high-efficiency solar cells. Ferroelectricity has been recognized as a critical issue in perovskite photovoltaics, although its existence and influence on photovoltaic performance remain controversial. We verify the ferroelectric polarization and reveal that it can suppress local photocurrent in CsFAMA through photoconductive atomic force microscopy (pc-AFM) and piezoresponse force microscopy (PFM). The time evolution of pc-AFM and PFM mappings first demonstrates that the photocurrents decreased with increasing electromechanical responses. Systematic characterization based on the first and second harmonic pointwise measurement as well as mappings shows that piezoelectricity primarily contributes to the measured electromechanical responses, while the ionic activity takes a back seat. Clear hysteresis loops and relaxation behaviors further confirm that the piezoresponse originates from ferroelectric polarization. Finally, based on temperature-dependent studies, we conclude that it is the ferroelectric polarization that weakens local photocurrent. This work provides insights into optimizing the photovoltaic performance of triple-cation mixed-halide perovskite solar cells.

Triple-cation mixed-halide perovskites have attracted considerable attention due to their excellent photovoltaic properties and enhanced stability, though the power conversion efficiency (PCE) is still far below the theoretical expectation. In order to understand the microscopic mechanisms responsible for the gap, a Cs-0.05(FA(0.85)MA(0.15))(0.95)Pb(I0.85Br0.15)(3) (CsFAMA)-based solar cell with respectful efficiency over 20% is examined, and distinct high- and low-current regions are observed in photoconductive atomic force microscopy (pc-AFM) mapping. Simulations attribute the difference in local photocurrents to interfacial donor defect densities at the NiO/CsFAMA interface, which is supported by electrochemical strain microscopy (ESM) mapping, revealing a negative correlation between ionic defects and photocurrents. The interfacial defects can be further manipulated by external bias upon relaxation study, resulting in reduced photocurrents accompanied by topography change when positive ions are driven toward the NiO/CsFAMA interface. It is also observed that both structure variation and photocurrent degradation upon accelerated aging test initiate at grain boundaries, which gradually expand at the expense of grain interior, suggesting that ionic defects are most active at grain boundaries. These findings render a direct correlation between interfacial defects and photocurrents while revealing degradation evolution, and if such interfacial defects heterogeneity can be mitigated, PCE toward the theoretical limit with enhanced stability can be envisioned.

Lithium-sulfur (Li–S) battery has now gradually emerged as the representative secondary energy storage battery of low cost, high security, and high theoretical specific capacity (1675 mAh g−1). However, the insulation properties of sulfur and shuttle issue of polysulfides between electrolytes lead to poor coulombic efficiency and performance of sulfur cathode. Therefore, we use metal–organic frameworks (MOFs) as pore-forming agent and glucose as primary carbon source to synthesize a honeycomb structured porous carbon (PC) material with high specific surface area (2151.9 m2 g−1) and large mesopore volume (2.16 cm3 g−1), which acts as the conductive skeleton for sulfur cathode. Furthermore, after mixing a trace of aluminum fluoride (AlF3) into sulfur electrode, the corresponding cycle performance and electrochemical stability have been further improved. The AlF3·3H2O/PC/S composition with 80 wt% sulfur loading exhibits the highest discharge capacity of 1298.1 mAh g−1 at the current density of 1 C and maintains at 455.6 mAh g−1 with ~ 99% coulombic efficiency after 500 cycles. This work supplies a facile and effective strategy for manufacture of more progressive porous carbonaceous sulfur host material and improving practical performance of Li–S batteries.

Moiré superlattices in van der Waals heterostructures are gaining increasing attention because they offer new opportunities to tailor and explore unique electronic phenomena. Using a combination of lateral piezoresponse force microscopy (LPFM) and scanning Kelvin probe microscopy (SKPM), we directly correlate ABAB and ABCA stacked graphene with local surface potential. We find that the surface potential of the ABCA domains is ∼15 mV higher (smaller work function) than that of the ABAB domains. First-principles calculations show that the different work functions between ABCA and ABAB domains arise from the stacking-dependent electronic structure. Moreover, while the moiré superlattice visualized by LPFM can change with time, imaging the surface potential distribution via SKPM appears more stable, enabling the mapping of ABAB and ABCA domains without tip-sample contact-induced effects. Our results provide a new means to visualize and probe local domain stacking in moiré superlattices along with its impact on electronic properties.

We displayed that the low-cost natural zeolite with molecular sieve structure can be used as the carrier of sulfur in lithium-sulfur batteries. Meanwhile, a simple salt-washing method was implemented on zeolite for dredging the internal microchannel to improve the ability of adsorption, ion exchange and sulfur loading. The experimental results show that the first specific discharge capacities of zeolite/S and salt-washed zeolite/S cathode under 0.2 C current density are 950.7 and 1 116.8 mAh/g, respectively, and corresponding discharge capacities remain at 350.6 and 604.2 mAh/g after 300 cycles. The first specific discharge capacity of salt-washed zeolite/S composite is 17.5% higher than that sample without salt-washing, and the corresponding ionic conductivity is improved.

Electrocatalytic water splitting, including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is an ideal method to produce hydrogen energy source. Stable electrocatalysts with good electrolytic activity are crucial for long-term water splitting. In this work, we show that MoO2 nanosheets can be grown directly on nickel foam substrate with oxygen vacancies decorated on the surface, acting as an excellent electrocatalyst for practical water splitting. In comparison to the pristine sample, the optimized MoO2, treated by 2% N2H4 solution for 20 min, exhibits a relatively low onset potential of -60 mV vs. reversible hydrogen electrode (RHE) for HER and a cell voltage of about 1.6 V vs. RHE to achieve a current density of 85 mA cm(-2 )for OER, which are attributed to the enhanced conductivity and improved surface active sites facilitated by oxygen vacancies. With the accelerated hydrogen generation process and activated water oxidation reaction, MoO2 is demonstrated to be a suitable and stable bifunctional electrode for full water splitting, and the post-treatment process for oxygen vacancies also provides an effective strategy for improving electrocatalysis. (C) 2020 Elsevier Ltd. All rights reserved.

Solid-state electrolytes have great potential in solving the intrinsic safety issues of conventional lithium-ion batteries utilizing liquid electrolytes, and there is a tremendous effort in developing solid-state electrolytes with improved ionic conductivity via microstructure engineering spanning multiple length scales. Nevertheless, there still lacks an effective method to probe the local ionic conductivity at the nanoscale with sufficient resolution, and thus how the microstructure impacts macroscopic ionic conductivity of solid-state electrolytes remains inadequately understood. Here, the newly developed sequential excitation (SE) electrochemical strain microscopy is applied to spatially resolve local electrochemical processes at the nanoscale, unraveling the ionic dynamics of grain boundary in Li1.3Al0.3Ti1.7(PO4)(3)solid-state electrolytes that correlate well with macroscopic impedance analysis. The high-conductivity sample possesses comparable ionic dynamics at grain boundary and within grain interior, while low-conductivity sample exhibits much higher resistance at the grain boundary, even though the conductivity of its grain interior is comparable to high-conductivity sample. The study thus provides direct experimental evidence on the bottlenecking grain boundaries in ionic conduction, and offers a powerful tool to study local ionic dynamics at the nanoscale in one-to-one correspondence to the microstructure features.

Ba(Ti0.80Zr0.20)O-3-0.5(Ba0.70Ca0.30)TiO3 (BTZ-0.5BCT) nanofibers (NFs) demonstrated diffusive phase transition, resulting in an enhanced Curie temperature TC. As a result, it is scientific significant to probe the variation of ferro/piezoelectricity during such diffusive phase transition region. In this letter, the ferro/piezoelectricity of BTZ-0.5BCT NF was probed by piezoelectric force microscopy (PFM) under a series of temperatures revealing the piezoresponse of BTZ-0.5BCT NF increased with temperatures as the temperature is less than 180 degrees C. The result shows that the first harmonic piezoresponse initially increased with temperatures, yet two singularities appeared at 120 and 180 degrees C, and subsequently rapidly decreased to less than room temperature, demonstrating the corresponding ferroelectric transition process was a diffusive phase transition. Such a diffusive phase transition is caused by the discontinuous internal nanostructure of the NF and the size effect of ferro/piezoelectricity originated from the nano-ceramics. More importantly, the principal ferroelectric phase transition of nano-ceramics during such diffusive phase transition region was further quantified by principal component analysis (PCA) study. This indicates that the principal TC of BTZ-0.5BCT nano-ceramics is around 180 degrees C, representing the TC of the whole BTZ-0.5BCT NF. Such a vivid description of the variated ferro/piezoelectricity with temperatures allows to provide a scientific method to quantify diffusive phase transition by PCA study. Copyright (C) EPLA, 2020

Glass-ceramic electrolytes are promising for all-solid-state batteries, yet their enhanced ionic conductivity is not well understood. We investigate structural difference between ceramic and glass-ceramic Li1.3Al0.3Ti1.7(PO4)3 tuned by boron, which is found to enhance conductivities of glass-ceramics by one order of magnitude, yet reduces that of ceramics. Raman and Magic Angle Spinning Nuclear Magnetic Resonance spectra indicate boron are primarily contained in glass phase, while electron energy-loss spectroscopy and high-resolution transmission electron microscopy reveal inhomogeneous distribution of boron and glassified grain boundaries. This substantially reduces interfacial resistance at grain boundaries with little effect on bulk resistance, which is further supported by spatial and spectroscopic electrochemical strain microscopy. The grain boundary resistance of ceramics, on the other hand, is increased by boron. We thus establish that lower interfacial resistance at glassified grain boundaries is responsible for higher conductivity in glass-ceramics, while boron can relax their grain boundaries even further.

Electrochemical conversion is typically studied at macroscopic scale, and it is quite challenging to probe local electrochemistry at the nanoscale, especially those involving multiple ions. Through a series of atomic force microscopy experiments, we demonstrate that two competing ionic strains arising from molar volume changes and electrochemical dipoles in a dual-ion system can reveal themselves in distinct relaxation behavior, enabling us to decouple their respective contributions and thus measure local diffusivity along with activation energy. Using soda-lime float glass as a model system, we observe a fast relaxation corresponding to diffusion of Na+ and a slow relaxation associated with electrochemical dipoles formed between Na+ and non-bridging oxygen. Assisted by simulations, we determine the local diffusivity of 5.64 x 107 16 m(2)/s and activation energy of 0.55eV for Na+ at 100 degrees C. The study provides a powerful tool to resolve local dynamics of dual ions, which can be applied to study a variety of complex energy conversion and storage systems.

Sodium-ion battery (SIB) is one of the most promising alternatives to partly substitute for lithium-ion batteries (LIBs), yet the large radius of Na+ leads to substantial volume change during sodiation/desodiation processes, resulting in inferior electrochemical performance. Na0.44MnO2 (NMO) possesses S-shaped Na+ diffusion pathway that can accommodate insertion/deinsertion of large Na+, though the poor electronic conductivity of NMO limits its ionic transport kinetics. Herein, single crystalline NMO nanorods (NRs) were synthesized, and their electronic conductivity was enhanced by one order of magnitude using reduced graphene oxide (rGO), as quantified by local conductive atomic force microcopy (c-AFM) measurement. When used as a cathode material for SIBs, NMO/rGO nanocomposite exhibits reversible specific capacities of 124mAh/g at 0.2C after 200 cycles and 70.8mAh/g at 15C, which are significantly enhanced over control cathode made of pure NMO NRs. Through detailed electrochemical impedance spectroscopy (EIS) analysis, it was found that NMO/rGO nanocomposite exhibits much reduced Warburg factor, resulting in enhanced Na+ diffusion at each discharging voltage platform. This suggests that the enhanced electronic conductivity helps Na+ insertion/deinsertion, resulting in improved electrochemical performance, and these insights help us understand how electronic conductivity improves ionic transport kinetics in SIBs.

Dynamic strain based atomic force microscopy (AFM) modes often fail at the interfaces where the most interesting physics occurs because of their incapability of tracking contact resonance accurately under rough topography. To overcome this difficulty, we develop a high-throughput sequential excitation AFM that captures contact dynamics of probe-sample interactions with high fidelity and efficiency, acquiring the spectrum of data on each pixel over a range of frequencies that are excited in a sequential manner. Using electrochemically active granular ceria as an example, we map both linear and quadratic electrochemical strain accurately across grain boundaries with high spatial resolution where the conventional approach fails. The enhanced electrochemical responses point to the accumulation of small polarons in the space charge region at the grain boundaries, thought to be responsible for the enhanced electronic conductivity in nanocrystalline ceria. The spectrum of data can be processed very efficiently by physics-informed principal component analysis (PCA), speeding data processing by several orders of magnitude. This approach can be applied to a variety of AFM modes for studying a wide range of materials and structures on the nanoscale.