National Laboratory of Solid State Microstructures

The g-C(3)N(4) photocatalyst was synthesized by directly heating the low-cost melamine. The methyl orange dye (MO) was selected as a photodegrading goal to evaluate the photocatalytic activity of as-prepared g-C(3)N(4). The comparison experiments indicate that the photocatalytic activity of g-C(3)N(4) can be largely improved by the Ag loading. The strong acid radical ion (SO(4)(2-) or NO(3)(-)) can promote the degrading rate of MO for g-C(3)N(4) photocatalysis system. The MO degradation over the g-C(3)N(4) is mainly attributed to the photoreduction process induced by the photogenerated electrons. Our results clearly indicate that the metal-free g-C(3)N(4) has good performance in photodegradation of organic pollutant.

Graphitic carbon nitride (g-C(3)N(4)) and boron-doped g-C(3)N(4) were prepared by heating melamine and the mixture of melamine and boron oxide, respectively. X-ray diffraction, X-ray photoelectron spectroscopy, and UV-vis spectra were used to describe the properties of as-prepared samples. The electron paramagnetic resonance was used to detect the active species for the photodegradation reaction over g-C(3)N(4). The photodegradation mechanisms for two typical dyes, rhodamine B (Rh B) and methyl orange (MO), are proposed based on our comparison experiments. In the g-C(3)N(4) photocatalysis system, the photodegradation of Rh B and MO is attributed to the direct hole oxidation and overall reaction, respectively; however, for the MO photodegradation the reduction process initiated by photogenerated electrons is a major photocatalytic process compared with the oxidation process induced by photogenerated holes. Boron doping for g-C(3)N(4) can promote photodegradation of Rh B because the boron doping improves the dye adsorption and light absorption of catalyst.

Recent developments in cadmium sulphide-based photocatalysts including heterojunctions, solid solutions and quantum dots for photocatalytic H₂ production are reviewed.

Perovskite solar cells (PSCs) emerging as a promising photovoltaic technology with high efficiency and low manufacturing cost have attracted the attention from all over the world. Both the efficiency and stability of PSCs have increased steadily in recent years, and the research on reducing lead leakage and developing eco-friendly lead-free perovskites pushes forward the commercialization of PSCs step by step. This review summarizes the main progress of PSCs in 2020 and 2021 from the aspects of efficiency, stability, perovskite-based tandem devices, and lead-free PSCs. Moreover, a brief discussion on the development of PSC modules and its challenges toward practical application is provided.

Hierarchical hollow carbon@Fe@Fe₃O₄ nanospheres were synthesized by a simple template method and another pyrolysis process.

The rod-like structure of MnO₂@Fe is apt to convert the electromagnetic wave to microcurrent and then attenuate it.

Single-phase, insulating Bi1−xLaxFeO3 (BLFOx, x=0.05, 0.10, 0.15, 0.20, 0.30, and 0.40) ceramics were prepared. An obvious phase transition from rhombohedral to orthorhombic phase was observed near x=0.30. It is found that the phase transition destructs the spin cycloid of BiFeO3 (BFO), and therefore, releases the locked magnetization and enhances magnetoelectric interaction. As a result, improved multiferroic properties of the BLFO0.30 ceramics with remnant polarization and magnetization (2Pr and 2Mr) of 22.4μC∕cm2 and 0.041emu∕g, respectively, were established.

The power conversion efficiency of photovoltaic devices based on semiconductor perovskites has reached ∼20% after just several years of research efforts. With concomitant discoveries of other promising applications in lasers, light-emitting diodes, and photodetectors, it is natural to anticipate what further excitement these exotic perovskites could bring about. Here we report on the observation of single photon emission from single CsPbBr3 perovskite nanocrystals (NCs) synthesized from a facile colloidal approach. Compared with traditional metal-chalcogenide NCs, these CsPbBr3 NCs exhibit nearly 2 orders of magnitude increase in their absorption cross sections at similar emission colors. Moreover, the radiative lifetime of CsPbBr3 NCs is greatly shortened at both room and cryogenic temperatures to favor an extremely fast output of single photons. The above superior optical properties have paved the way toward quantum-light applications of perovskite NCs in various quantum information processing schemes.

In this paper, we demonstrate transparent metaholograms based on silicon metasurfaces that allow high-resolution grayscale images to be encoded. Finally, the holograms feature the highest diffraction and transmission efficiencies, and operate over a broad spectral range.

Typical lead-free energy storage systems and their performances for dielectric and multilayer capacitors over the last decade.

Single-phase insulating BiFeO3 ceramics have been synthesized by a simple but effective method that conventional solid state reaction is followed immediately by quenching processing. At room temperature, the ceramics show a metastable, distorted rhombohedral phase and the refined structure parameters are presented based on x-ray diffraction. It is revealed that the formations of Fe2+ and oxygen deficiency are greatly suppressed by the quenching processing. A well-saturated ferroelectric hysteresis loop with a large remnant polarization (2Pr=23.5μC∕cm2) is observed with an applied field of 155kV∕cm. Temperature-dependent magnetic property is investigated and weak ferromagnetism with a remnant magnetization of 4×10−6μB∕Fe at 10K is established. These results may have implications for further studies on multiferroics.

We have conducted an experimental and theoretical study on first- and second-order Raman scattering of zinc blende and wurtzite ZnS. Based on the calculated phonon band structure, phonon density of states, and symmetry selection rules, we have clearly identified for the first time the origins of these vibration modes in the second-order Raman spectra from these two polymorphs. For zinc blende ZnS, it is found that the previously estimated frequency of the LA mode at X point in the Brillouin-zone boundary is much smaller than the value obtained from other experiments and our calculation. Considering the involvement of LA phonon at X point, we reassign the second-order Raman active modes and some other modes which have not yet been understood so far. This work clarifies some of the controversial Raman mode assignments in zinc blende and wurtzite ZnS.

Perovskite (PVSK) photovoltaic (PV) devices are undergoing rapid development and have reached a certified power conversion efficiency (PCE) of 26.1% at the cell level. Tremendous efforts in material and device engineering have also increased moisture, heat, and light-related stability. Moreover, the solution-process nature makes the fabrication process of perovskite photovoltaic devices feasible and compatible with some mature high-volume manufacturing techniques. All these features render perovskite solar modules (PSMs) suitable for terawatt-scale energy production with a low levelized cost of electricity (LCOE). In this review, the current status of perovskite solar cells (PSCs) and modules and their potential applications are first introduced. Then critical challenges are identified in their commercialization and propose the corresponding solutions, including developing strategies to realize high-quality films over a large area to further improve power conversion efficiency and stability to meet the commercial demands. Finally, some potential development directions and issues requiring attention in the future, mainly focusing on further dealing with toxicity and recycling of the whole device, and the attainment of highly efficient perovskite-based tandem modules, which can reduce the environmental impact and accelerate the LCOE reduction are put forwarded.

Photocatalysts possessing high efficiency in degrading aquatic organic pollutants are highly desirable. Although graphene-based nanocomposites exhibit excellent photocatalytic properties, the role of graphene has been largely underestimated. Herein, the photothermal effect of graphene-based nanocomposites is demonstrated to play an important role in the enhanced photocatalytic performance, which has not been considered previously. In our study on degradation of organic pollutants (methylene blue), the contribution of the photothermal effect caused by a nanocomposite consisting of P25 and reduced graphene oxide can be as high as ∼38% in addition to trapping and shuttling photogenerated electrons and increasing both light absorption and pollutant adsorptivity. The result reveals that the photothermal characteristic of graphene-based nanocomposite is vital to photocatalysis. It implies that designing graphene-based nanocomposites with the improved photothermal performance is a promising strategy to acquire highly efficient photocatalytic activity.

Polycrystalline Bi1−xNdxFeO3 (x=0–0.15) thin films were prepared on (111) Pt∕Ti∕SiO2∕Si substrates via metal organic deposition method. The effect of Nd dopant on the structural, electric, and magnetic properties was studied. It was found that the ferroelectric polarization and saturation magnetization of the films were enhanced by appropriate Nd doping due to the structural distortion and the suppressed cycloidal spin structure. Meanwhile, Nd-doped BiFeO3 thin films exhibited magnetic anisotropy because of the magnetocrystalline anisotropy.

InI₃, a self-defense redox mediator, can form a pre-deposited indium layer to resist the synchronous attack on a Li anode by the soluble I₃⁻, and hence can suppress the shuttle effect in lithium–O₂ batteries.

The inverse magnetocaloric effect associated with the martensitic transition in the Ni45.4Mn41.5In13.1 Heusler alloy is reported. A large positive magnetic entropy change of 8J∕kgK under a low magnetic field of 10kOe is found near the martensitic transition temperature. This change originates from the first-order transition from a low-temperature weak-magnetic martensitic phase to a high-temperature ferromagnetic austenitic phase. The large low-field magnetic entropy change indicates a great potential of Ni–Mn–In alloys as working materials for magnetic refrigeration in a wide temperature range.

Further understanding the underpinning chemistry and electrochemistry that govern the properties of polymer electrolytes for solid-state lithium–air batteries.

Bismuth sulfide nanorods have been successfully prepared by a sonochemical method from an aqueous solution of bismuth nitrate and sodium thiosulfate in the presence of complexing agents. Bismuth sulfide nanorods with different diameters and lengths could be obtained by using different complexing agents including ethylenediaminetetraacetic acid, triethanolamine, and sodium tartrate. Bi2S3 nanorods have also been successfully prepared by choosing thioacetamide as the sulfur source. When 20% N,N-dimethylformamide was used as the solvent, higher yield was observed and smaller sizes of Bi2S3 nanorods were obtained. The products were characterized by powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction, high-resolution transmission electron microscopy, IR spectroscopy, and X-ray photoelectron spectroscopy. Probable mechanisms for the sonochemical formation of Bi2S3 nanorods in aqueous solutions are proposed.

The low-field magnetic entropy changes in Ni50−xMn39+xSn11 alloys (x=5, 6, and 7) were investigated. The martensitic transition shifts to lower temperature with the increase of Mn concentration. Under an applied magnetic field of 10kOe, the magnetic entropy changes are 6.8, 10.1, and 10.4J∕kgK, for x=5, 6, and 7, respectively. The large entropy change in Ni50−xMn39+xSn11 can be attributed to the sharp magnetization change associated with the martensitic transition from a ferromagnetic parent phase to a weak-magnetic martensitic phase. The large low-field magnetic entropy change and low cost suggest Ni50−xMn39+xSn11 alloy as the promising magnetic refrigerant.