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Molecular ferroelectrics with excellent ferroelectric properties and a low processing temperature, a narrow bandgap, and light weightiness have shown great potential in the photovoltaic field. However, two-dimensional (2D) perovskite solar cells with high tunability, excellent photo-physical properties, and superior long-term stability are limited by the poor out-of-plane conductivity from intrinsic multi-quantum well electronic structures. This work uses 2D molecular ferroelectric as the absorbing layer to break the limit of multiple quantum wells. Our 2D ferroelectric solar cells achieve the highest open-circuit voltage (1.29 V) and the best efficiency (3.71%) among the 2D (n = 1) Ruddlesden–Popper perovskite solar cells due to the enhanced out-of-plane charge transport induced by molecular ferroelectrics with a strong saturation polarization, high Curie temperature, and multiaxial characteristics. This work aims to break the inefficient out-of-plane charge transport caused by the limit of multi-quantum well electronic structure and improve the efficiency of 2D ferroelectric solar cells.

Ni-Co bimetallic catalysts supported on coconut shell activated carbon are synthesized using solid-phase method and investigated for dry reforming of methane, to explore the impact of Ni:Co ratio on the catalyst activity and stability. The catalyst performances are evaluated under the temperature varying from 600 to 900 °C and gas hourly space velocity (GHSV) of 7200 mL/h·g-cat. The characterization results show that metal nanoparticles are produced on the support, and the bimetallic catalyst with an explicit Ni:Co ratio (2:1) is the most beneficial for metal particle dispersion and acquires the minimum particle size of 4.41 nm. The bimetallic catalysts with an explicit Ni:Co ratio of 1:2 and 1:1 exhibit a synergistic effect towards the conversions of CH

In this study, a new method of microwave-induced discharge over biomass-derived char (i.e., bio-char) spherical carriers was proposed. Bio-char spherical carriers were obtained through rational forming. The discharge intensity and temperature increase under discharge were measured to elaborate the quantitative relationship between microwave discharge and the temperature increase. The effect of bio-char properties on microwave-induced discharge was investigated. The results revealed that discharge achieved the highest electric–thermal conversion efficiency of 61.04%, and the heat generation ratio through the discharge in the initial 10 min was up to 69.08%. The graphitisation degree and transmission depth of microwaves can affect discharge intensity. A critical light intensity inducing hot spot effect exists under different working conditions, and exceeding the critical value led to the hot spot effect and a sudden increase in bed temperature, with a corresponding range of 2.48–5.76 V. The maximum temperature under microwave discharge reached 981 °C, with a heating rate of 376.4 °C/min. The method is potential in the field of value-added utilization of bio-char and microwave-promoted chemical processes.

Adding ferromagnetism into semiconductors attracts much attentions due to its potential usage of magnetic spins in novel devices, such as spin field-effect transistors. However, it remains challenging to stabilize their ferromagnetism above room temperature. Here we introduce an atomic chemical-solution strategy to grow wafer-size NiO thin films with controllable thickness down to sub-nanometer scale (0.92 nm) for the first time. Surface lattice defects break the magnetic symmetry of NiO and produce surface ferromagnetic behaviors. Our sub-nanometric NiO thin film exhibits the highest reported room-temperature ferromagnetic behavior with a saturation magnetization of 157 emu/cc and coercivity of 418 Oe. Attributed to wafer size, the easily-transferred NiO thin film is further verified in a magnetoresistance device. Our work provides a sub-nanometric platform to produce wafer-size ferromagnetic NiO thin films as atomic layer magnetic units in future transparent magnetoelectric devices.

The development of atomically thin single crystal films is necessary to potential applications in the 2D semiconductor field, and it is significant to explore new physical properties in low-dimensional semiconductors. Since, zero-dimensional (0D) materials without natural layering are connected by strong chemical bonds, it is challengeable to break symmetry and grow 0D Cs

Molybdenum ditelluride (MoTe2) has attracted ever-growing attention in recent years due to its novel characteristics in spintronics and phase-engineering, and an efficient and convenient method to achieve large-area high-quality film is an essential step toward electronic applications. However, the growth of large-area monolayer MoTe2 is challenging. Here, for the first time, we achieve the growth of a centimeter-sized monoclinic MoTe2 monolayer and manifest the mechanism of immobilized precursor particle driven growth. Microscopic characterizations reveal an obvious trend of immobilized precursor particles being consumed by the monolayer and continuing to provide a source for the growth of the monolayer. Time-of-flight secondary ion mass spectrometry verifies the attachment of hydroxide ions on the surface of the MoTe2 monolayer, thereby realizing the inhibition of crystal growth along the [001] zone axis and the continuous growth of the MoTe2 monolayer. The first-principles DFT calculations prove the mechanism of immobilized precursor particles and the absorption of hydroxide ions on the MoTe2 monolayer. The as-grown MoTe2 monolayer exhibits a surface roughness of 0.19 nm and average conductivity of 1.5 × 10-5 S/m, which prove the smoothness and uniformity of the MoTe2 monolayer. Temperature-dependent electrical measurements together with the transfer characteristic curves further demonstrate the typical semimetallic properties of monoclinic MoTe2. Our research elaborates the microscopic process of immobilized precursor particles to grow large-area MoTe2 monolayer and provides a new thinking about the growth of many other two-dimensional materials.

Monolayer transition metal dichalcogenides (TMDs) show promising potential for next-generation optoelectronics due to excellent light capturing and photodetection capabilities. Photodetectors, as important components of sensing, imaging and communication systems, are able to perceive and convert optical signals to electrical signals. Herein, the large-area and high-quality lateral monolayer MoS2/WS2 heterojunctions were synthesized via the one-step liquid-phase chemical vapor deposition approach. Systematic characterization measurements have verified good uniformity and sharp interfaces of the channel materials. As a result, the photodetectors enhanced by the photogating effect can deliver competitive performance, including responsivity of ~ 567.6 A/W and detectivity of ~ 7.17 × 1011 Jones. In addition, the 1/f noise obtained from the current power spectrum is not conductive to the development of photodetectors, which is considered as originating from charge carrier trapping/detrapping. Therefore, this work may contribute to efficient optoelectronic devices based on lateral monolayer TMD heterostructures.

All-inorganic perovskite solar cells suffer from low performance due to unsatisfactory carrier transport and light harvesting efficiency. Semiconductor nanopillar arrays can reduce light reflection loss and suppress exciton recombination dynamics in optoelectronic devices. In all-inorganic perovskite solar cells, few studies employing TiO2 nanopillar arrays (TiO2 NaPAs) have been reported to improve the device performance. Herein, well-arranged TiO2 NaPAs are chosen to enhance the interfacial contact between perovskite and electron transporting layers for improving the carrier transport. Notably, TiO2 NaPAs can be directly fabricated on rigid/flexible substrates at roughly room temperature by unique glancing angle deposition, which is more available than high-temperature hydrothermal/solvothermal methods. By embedding TiO2 NaPAs into chemical processable CsPbI2Br layers, continuous and intimate films are readily formed, guaranteeing large physical contact for facilitating more effective electron injection and charge separation. The vertically grown TiO2 NaPAs also provide a straightforward electron transporting path to electrodes. In addition, TiO2 NaPAs can guide the incident light and enhance the light-harvesting ability of CsPbI2Br films. As a result, the solar cell with TiO2 NaPAs displays a power conversion efficiency of 11.35% higher than planar control of 10.04%, and exhibits better long-term thermal stability. This strategy provides an opportunity by constructing direct interfacial regulation towards the performance improvement of inorganic perovskite solar cells.

Two-dimensional materials have been demonstrated as promising toolboxes for optoelectronics. Transition metal carbides and nitrides (MXenes), members of an emerging family of two-dimensional materials, have drawn extensive attention in optoelectronics owing to their excellent conductivity and tunable electronic properties. Herein, a photodetector based on the two-dimensional van der Waals heterostructure of Ti3C2Tx MXene and a MoS2 monolayer was constructed to observe the ambipolar photoresponse, which showed a positive photoresponse in the visible spectrum (500–700 nm) and a negative photoresponse at longer wavelengths (700–800 nm). The device exhibited a high negative responsivity of 1.9 A/W and a detectivity of 2.1 × 1010 Jones under 750 nm light illumination. Detailed experiments demonstrate that the negative photoresponse arises from the heterostructure-induced trap energy level, which confines the excited photoelectrons and leads to an inverse current. This work demonstrates a unique optoelectronic phenomenon in MoS2/MXene heterostructures and provides valuable insights into the development of new photodetection materials.

To overcome water instability and low photocatalytic activity of lead-free halide perovskite for the degradation of organic dyes, we report a novel photocatalyst of lead-free halide perovskite with Na incorporation and employ it for the photocatalytic degradation of organic dyes in water solution under visible light irradiation. The main purpose of this work is to confirm the feasibility of lead-free halide perovskite with Na incorporation for improving the photocatalytic efficiency and recyclability in water solution and further to explore the mechanism behind the enhancement of photocatalytic performance after Na incorporation. The results show that Cs2Ag0.60Na0.40InCl6 can increase the dye degradation rate by at least 50% than the lead-free halide perovskite (Cs2AgInCl6) and the photocatalyst of Ag substituted by Na (Cs2NaInCl6). The degradation efficiency of rhodamine 6G catalyzed by Cs2Ag0.60Na0.40InCl6 reaches 94.94% over 60 min, which is 72% higher than that catalyzed by Cs2NaInCl6 and 27% higher than that catalyzed by Cs2AgInCl6. What's more, the degradation efficiency of methyl orange catalyzed by Cs2Ag0.60Na0.40InCl6 is 90.39% within 150 min, which is 66% higher than that catalyzed by Cs2NaInCl6 and 54% higher than that catalyzed by Cs2AgInCl6. Moreover, the photocatalyst of Cs2Ag0.60Na0.40InCl6 exhibits a desirable recyclability by water exposure, retaining the degradation efficiency over 90% after five cycles. The strengthened photocatalytic performance in the presence of Cs2Ag0.60Na0.40InCl6 is ascribed to an increase of radiative recombination rate and an improvement of average lifetime to 204 ns since an appropriate Na incorporation at the atomic ratio of Na/Ag=4:6 breaks the original crystal lattice and meanwhile increases the electron and hole overlap. The work proves a great potential of halide perovskite with Na incorporation for the highly efficient photocatalytic degradation of organic dyes in water solution.

Multifunctional devices are of great interest for integration and miniaturization on the same platform, but simple addition of functionalities would lead to excessively large devices. Here, the photodetection and chemical sensing device is developed based on two-dimensional (2D) glassy-graphene that meets similar property requirements for the two functionalities. An appropriate bandgap arising from the distorted lattice structure enables glassy graphene to exhibit comparable or even improved photodetection and chemical sensing capability, compared with pristine graphene. Due to strong interactions between glassy graphene and the ambient atmosphere, the devices are less sensitive to photoinduced desorption than the ones based on graphene. Consequently, the few-layer glassy graphene device delivers positive photoresponse, with a responsivity of 0.22 A W−1 and specific detectivity reaching ∼1010 Jones under 405 nm illumination. Moreover, the intrinsic defects and strain in glassy graphene can enhance the adsorption of analytes, leading to high chemical sensing performance. Specifically, the extracted signal-to-noise-ratio of the glassy graphene device for detecting acetone is 48, representing more than 50% improvement over the device based on graphene. Additionally, bias-voltage- and thickness-dependent volatile organic compound (VOC) sensing features are identified, indicating the few-layer glassy graphene is more sensitive. This study successfully demonstrates the potential of glassy graphene for integrated photodetection and chemical sensing, providing a promising solution for multifunctional applications further beyond.

The construction of aqueous Zn-ion hybrid capacitors (ZICs) reconciling high energy/power density is practically meaningful yet remains a grand challenge. Herein, a high-capacitance and long-life Z...

Electrochemical nitrogen fixation provides an environmentally friendly strategy for producing ammonia (NH3) under ambient conditions. However, an inexpensive and efficient electrocatalyst for the electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions is still needed. Herein, we report an efficient non-noble-metal electrocatalyst consisting of large scaled-up monocrystalline 3R MoS2, which is first utilized as an electrocatalyst for the NRR under ambient conditions. The NRR performance can be optimized via improving the electrochemically active surface area (ECSA) of MoS2. The NH3 yield rate and FE of MoS2-700 reach 8.8 μg h−1 mgcat−1 and 1.9%, respectively. Notably, 3R MoS2-700 shows excellent stability, with the negligible fluctuation of electrocatalytic activity after being recycled seven times. This study may provide a new strategy for structuring efficient electrocatalysts for the NRR.

Enhancing the built-in electric field to promote charge dynamitic process is of great significance to boost the performance of the non-fullerene organic solar cells (OSCs), which has rarely been concerned. In this work, we introduced a cheap ferroelectric polymer as an additive into the active layers of non-fullerene OSCs to improve the device performance. An additional and permanent electrical field was produced by the polarization of the ferroelectric dipoles, which can substantially enhance the built-in electric field. The promoted exciton separation, significantly accelerated charge transport, reduced the charge recombination, as well as the optimized film morphology were observed in the device, leading to a significantly improved performance of the PVDF-modified OSCs with various active layers, such as PM6 : Y6, PM6 : BTP-eC9, PM6 : IT-4F and PTB7-Th : Y6. Especially, a record efficiency of 17.72 % for PM6 : Y6-based OSC and an outstanding efficiency of 18.17 % for PM6 : BTP-eC9-based OSC were achieved.

Spinel oxides have been considered as promising precious metal-free catalysts for oxygen reduction reaction (ORR). However, the poor intrinsic conductivity and moderate electrocatalytic performance hinder their practical applications. Hence, various strategies have been explored and reported in addressing the issues. Herein, an elaborate approach for enhancing the ORR performance of spinel NiCo2O4 is proposed, by combining the decoration of NiCo2O4 nanoparticles on electrospun carbon nanofibers and defect engineering with rich oxygen vacancies on NiCo2O4 nanoparticles through a facilely controlling on calcination circumstance, which could not only increase more active sites and improve the intrinsic catalytic activity, but also render an excellent stability for long-term operation. Thus, the as-prepared hybrid exhibits significantly improved ORR electrocatalytic performance, including a high limited current density of −5.8 mA cm−2, a positively shifting of the onset potential at 0.88 V and half-wave potential at 0.76 V (vs. RHE). The performance of rechargeable Zn-air battery based on the as-prepared catalyst surpasses the one based on Pt/C catalyst significantly. This work can be also applied to other metal oxides based electrocatalysts, and then provided an avenue for the realization of metal-air batteries and fuel cells with high efficient and cost-effective.

Controllable nucleation sites play a key role in the selective growth of heterostructures. Here, we are the first to report a one-pot strategy to realize the confined and selective growth of large MoS2/WS2 lateral and vertical heterostructures. A hydroxide-assisted process is introduced to control the nucleation sites, thereby realizing the optional formation of lateral and vertical heterostructures. Time-of-flight secondary ion mass spectrometry verifies the critical role of hydroxide groups toward the controllable growth of these heterostructures. The size of the as-grown MoS2/WS2 lateral heterostructures can be as large as 1 mm, which is the largest lateral size reported thus far. The obtained MoS2/WS2 heterostructures have a high carrier mobility of ∼58 cm2 V-1 s-1, and the maximum on/off current ratio is >108. This approach provides not only a pathway for the selective growth of large MoS2/WS2 lateral and vertical heterostructures but also a fundamental understanding of surface chemistry for controlling the selective growth of transition-metal dichalcogenide heterostructures.

Nowadays, casted multicrystalline silicon is the most important material in photovoltaic industry. In order to reduce the cost of silicon ingots, the recycle of silicon ingot tailings is explored. In this paper, the secondary utilization of silicon block tailings with a thickness of 25 mm, matched with process of diamond wire saw machine was studied. The comparative analysis on technical parameters of bottom red zone and wafers generated by virgin crushed polycrystalline silicon feedstock and secondary utilized tailings was discussed. The result shows that recycle of tailing seeds is feasible. The above-mentioned tailings of diamond wire saw ingots shall be with a thickness of 25 mm. The bottom red zone of area paved by tailings is 2 mm longer than that in area paved by virgin crushed polycrystalline silicon feedstock. But the difference of cell conversion efficiency is negligible, 0.01% lower. Consequently, it is feasible to recycle high-efficiency multicrystalline ingots tailings, which push forward further cost reduction of high-efficiency multicrystalline ingots.

Based on first-principles density functional theory calculations, we investigated a modified routine using hydroxyl adsorption that recently demonstrated the controlled growth of MoS2 monolayers. The new growth approach impedes the deposition of a second MoS2 layer; however, the hydroxyl adsorption and its effects have been mostly unexplored. Through this study, we first explored the adsorption behaviors of the hydroxyl radical (OH) on monolayer MoS2 and briefly discussed its effects on the stability and electronic structure. Monolayer MoS2 repels charged OH–, whereas the adsorption of the neutral OH radical is energetically favorable; the corresponding adsorption energies are 0.09 eV and −1.35 eV, respectively. The diffusion barrier of the OH radical on MoS2 is 0.52 eV, indicating that the molecule can quickly diffuse. Next, the study demonstrated that for multiple OH adsorptions, a concerted reaction including OH dissociation and H2O formation is more energetically favorable than the adsorption of two OH molecules by 2.50 eV, which in turn results in a mixed adsorption configuration of O and OH. In addition, we revealed that the OH adsorption creates a mid-gap state and facilitates the reconstruction of the MoS2 edge.

3D printing technology has stimulated a burgeoning interest to fabricate customized architectures in a facile and scalable manner targeting wide ranged energy storage applications. Nevertheless, 3D-printed hybrid capacitor devices synergizing favorable energy/power density have not yet been explored thus far. Herein, we demonstrate a 3D-printed sodium-ion hybrid capacitor (SIC) based on nitrogen-doped MXene (N-Ti3C2Tx) anode and activated carbon cathode. N-Ti3C2Tx affording a well-defined porous structure and uniform nitrogen doping can be obtained via a sacrificial template method. Thus-formulated ink can be directly printed to form electrode architecture without the request of a conventional current collector. The 3D-printed SICs, with a large areal mass loading up to 15.2 mg cm-2, can harvest an areal energy/power density of 1.18 mWh cm-2/40.15 mW cm-2, outperforming the state-of-the-art 3D-printed energy storage devices. Furthermore, our SIC also achieves a gravimetric energy/power density of 101.6 Wh kg-1/3269 W kg-1. This work demonstrates that the 3D printing technology is versatile enough to construct emerging energy storage systems reconciling high energy and power density.

Earth-abundant elements are highly desirable electrocatalysts for artificial N2 fixation (NRR). However, most earth-abundant elements are inactive for the NRR, and the competitive hydrogen evolution reaction (HER) causes inferior faradaic efficiency. Thus, facile modification methods to transform an NRR-unfavorable electrocatalyst into its NRR-favorable counterpart are highly demanded. Herein, we present an efficient hydrophobic carbon layer incorporation strategy on tin monosulfide (SnS@C) to greatly boost the NRR activity of SnS. The hydrophobic carbon layer can limit proton availability at the electrode surface while integrating the advantages of strong N2 adsorption and better conductivity that synergistically improve the NRR performance. Specifically, SnS@C delivers a high faradaic efficiency of 14.56% and NH3 yield of 7.95 × 10−11 mol s−1 cm−2 (24.33 μgNH3 h−1 mgcat−1) at −0.5 V versus the reversible hydrogen electrode. It also exhibits durable stability for consecutive electrolysis over 18 h. Adequate control and 15N isotopic labeling experiments confirm the reliability of N sources. Density functional theory calculations reveal that the superior activity is attributed to the redistribution and bias of electrons between the SnS and carbon-layer interface. This work highlights that the simple hydrophobic carbon layer incorporation strategy could guide the design and modification of advanced NRR catalysts.