Functional Materials Letters

Efficient electron selective contacts, smoother rear silicon surface and passivation of silicon-electrode interfaces could reduce parasitic light absorption and electron-hole recombination. Therefore, they are necessary for high conversion efficiency in silicon solar cells. In this work, a novel transition metal doped glass frit is fabricated and introduced into pristine Al paste. As a result, the average power conversion efficiency (PCE) of cells is improved from 17.9 to 18.3%. Combining several results, the improvement can be attributed to three key factors: (a) a thicker back surface field (BSF) layer that blocks electrons; (b) a smoother rear silicon surface which leads to less parasitic absorption; and (c) glass frit coating on aluminum particles which may facilite hole-transfer from silicon layer to aluminum electrode.

In this paper, orthoferrite YFeO₃ was synthesized by hydrothermal method. The space group of YFeO₃ is Pnma and the spin state of ${\text{Fe}}^{3+}$ ion is low spin (LS). The YFeO₃ crystal exhibits a weak antiferromagnetic behavior by magnetic measurement. For the electrical polarization measurement, micron-scale Pt electrodes were deposited on the both sides of the YFeO₃ crystal by FIB-induced deposition. The saturation polarization value is 0.1994$\mu$C/cm² at room temperature. The crystal exhibits ferroelectric behavior through the Dzyaloshinskii–Moriya interaction induced by additional spin canting of the antiferromagnetic ordering. This work may be applied to further study of the multiferroicity in rare-earth orthoferrites RFeO₃.

Artificial muscle actuators demonstrate great potential for improving the quality of life. Recently, polymer muscle actuators have attracted attention due to their inexpensive and highly versatile methods of fabrication along with decent mechanical properties that can mimic those of natural muscles. The aim of this research is to investigate the usability of a magnetite-doped polymer powder, polydimethylsiloxane (PDMS), for artificial muscle actuators through an inexpensive method of production. PDMS samples doped with different levels of magnetite were fabricated using molds that were produced by additive manufacturing. Subsequently, the samples were magnetically and mechanically characterized by investigation of strength, elastic modulus, failure strain and permittivity, which are vital to meet the load capacity. The test results demonstrated that the mechanical and magnetic properties could be tailored as a function of doping level. Matching the mechanical response of these artificial components to those of artificial muscles will reduce the residual stresses, enhance the artificial muscle life and allow wider use of these materials for biomedical applications. This research rendered fabrication of molds possible for various applications where geometric customization of the actuator is required to meet endure severe loads, thanks to the freeform nature of additive manufacturing.

With sodium alginate and graphene oxide (GO) as raw materials, cobalt alginate/GO aerogel was prepared by ion-exchange reaction and subsequent freeze-drying technique. The aerogel was transported into a Co/N-rGO composite material through high-temperature carbonization at ammonia atmosphere. The Co/N-rGO composite material was then used for catalyzing oxygen reduction reaction in fuel cell and showed excellent catalytic activity and stability.

A novel graphene-based solid acid was successfully prepared through loading Co and Ni onto the surface of reduced graphene nanosheets with hydrothermal method. After sulfonation of the as-synthesized reduced graphene oxide (rGO)-Ni-Co composites, a kind of solid acid was prepared for reducing p-Nitrophenol (PNP) into p-Aminophenol (PAP). The result shows that the sulfonated rGO-Ni-Co composites have better catalytic ability than rGO-Ni-Co composites. These findings may provide a facile method to prepare solid acid which consists of rGO and metal ion for its application in catalysis fields.

The development of ferroelectric photovoltaic (FE-PV) materials has been limited for a long time due to their large bandgap. Many strategies for lowering the bandgap have been suggested to promote FE-PV properties. The effects of magnetic ordering and B-site-cation ordering to lower the bandgap of FE-PV are investigated in this paper using first-principles calculations. Results show that the most stable structure of tetragonal Bi₂FeCrO₆ ($t$-Bi₂${\text{FeCrO}}_6)$ is the AS1 structure (Fe/Cr alternate stacking ordering) with C-type antiferromagnetic ordering (defined as AC-$t$-Bi₂FeCrO₆), which has a small bandgap, suggesting that AC-$t$-Bi₂FeCrO₆ is among the FE-PV materials with the highest application potential.

As promising hydrogen carriers, sodium borohydride (SB) and ammonia borane (AB) can controllably release pure hydrogen by means of catalytic hydrolysis at mild condition. In this work, we introduced a novel and facile method for transformation of commercial nickel foam (NF) to highly active 3D porous Ni–Zn catalyst. The method consisted of three steps including electroplating zinc on NF, alloying treatment and chemical etching. Catalyst microstructure and component were characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Hydrogen generation measurement indicates that the prepared Ni–Zn catalyst is highly efficient for catalytic hydrolysis of SB and AB to generate hydrogen. Moreover, recycling performance of the catalyst was also investigated.

Lithium-sulfurized polyacrylonitrile battery is a promising candidate among lithium metal batteries. Nevertheless, the formation of Li dendrites is recognized the worst problem for battery. In this study, we demonstrate an air-stable prelithiation technology for highly reversible Li ion-S@PAN battery. A sandwich-like structure is designed for a lithium–silicon/graphite compound, which not only prevent attack of the lithium surface from humid air, but also improve the lithiation progress more convenient and reliable. When test in Li ion-sulfurized polyacrylonitrile battery, a specific capacity up to 560mAh${\text{g}}^{-1}$, and only 24% capacity loss is witnessed after 1500 cycles at 1000mA${\text{g}}^{-1}$.

MoS₂/SnS₂ composite material with satisfactory electrochemical performance has been prepared through a facile two-step hydrothermal method followed by high temperature sintering. The as-synthesized nanocomposite exhibits both excellent reversible capacity and improved cycling durability as the anode material of sodium ion batteries. Based on electrochemical test results, MoS₂/SnS₂ shows an incipient capacity of 750mAh/g and a capacity reservation of 600mAh/g after 100 cycles at the current of 0.1A/g. Such a combination of MoS₂ nanosheets and SnS₂ nanoparticles alleviates the agglomeration problem and attributes strong synergic effect, making MoS₂/SnS₂ composite a potential sodium ion battery anode.

Fe-Ni-Co-Al-Ta polycrystalline shape memory alloys have received extensive attention due to their excellent properties such as huge superelasticity, high strength and high damping. We herein report that Fe-Ni-Al-Ta polycrystalline alloys also have excellent superelasticity, which can exhibit a large superelastic strain of more than 17% in compression at room temperature. This superelasticity has slim hysteresis and is greatly affected by the content of Ta in the alloys. In this work, Fe-Ni-Al-Ta shape memory alloys reveal some characteristics that are different from the reported Fe-Ni-Co-Al-based shape memory alloys.

Antimony-doped tin dioxide (ATO)-coated TiO₂ (TiO₂@ATO) composite was synthesized by a polymeric precursor method with lactic acid as the chelating agent. The structural and morphological characterizations of the as-fabricatied TiO₂@ATO composite were investigated by XRD, FTIR, SEM, TEM and XPS. The resistivity was also examined by electrical resistance measurements. The theoretical calculations were introduced for elucidating the change of bandgap from the microscopic level. The results showed that the lowest resistivity of TiO₂@ATO composite they could be achieved was 1.69 $\mathrm{\Omega }\cdot \mathrm{\text{cm}}$. TiO₂@ATO composite possessed a core–shell structure with the ATO shell thickness of 13–16nm. The as-prepared ATO nanoparticles were in rutile phase and with 4.3–7.0nm in diameter (calcinated at 550^∘C). The ATO grain growth during the calcination process could be viewed as consisting of two stages: the activation energies were calculated to be $3.98\pm 0.14$kJ/mol and $9.90\pm 0.53$kJ/mol, respectively.

This paper reports the synthesis MoS₂/graphene composite as an anode using commercial graphene as conductive enhancer and structural modifier. X-ray powder diffraction (XRD) and morphology details show that the as-synthesized MoS₂/graphene composite has hexagonal structure and shows three-dimensional hierarchical network structure. The anode electrochemical properties of MoS₂/graphene composite and pure MoS₂ were measured and analyzed by galvanostatic charge–discharge cycling vs. Na/Na⁺ at different current densities in 0.05–3.0V. Compared to pure MoS₂, MoS₂/graphene composite demonstrates great specific capacity (509mAh${\text{g}}^{-1}$ at the current rate about 0.3 C), excellent rate capability (305mAh${\text{g}}^{-1}$ at the maximum current rate 5 C) and relatively good cycle-life (capacity reached 84% after 100 cycles). Moreover, the facile synthesis strategy of MoS₂/graphene can provide a reference for designing other transition metal chalcogenides composites containing graphene for high performance SIBs.

The influences of the crystal structure of Zr-doped lithium titanate prepared by the sol–gel method on the lithium ion diffusion coefficient and rate performance were studied. Compared with the pure phase Li₄Ti₅O${}_{12}$, Zr-doped lithium titanate presented a high discharge capacity as well as a good rate performance and cycle performance, and Li₄Zr${}_{0.05}$Ti${}_{4.95}$O${}_{12}$ yielded the best electrochemical performance. Li₄Zr${}_{0.05}$Ti${}_{4.95}$O${}_{12}$ possessed capacities of 162 (1st) and 143 (100th) mAh g${}^{-1}$ at 5mAcm${}^{-2}$ with $\sim$100% of the coulombic efficiency. The area of the migration surface of Li₄Ti₅O${}_{12}$ is proportional to the square of the lattice constant, so Li₄Zr${}_{0.05}$Ti${}_{4.95}$O${}_{12}$ demonstrated the largest migration surface with 8.3600 Å of “$a$”. The larger the migration surface is, the lower the activation energy for lithium ion migration is, and the easier it is for lithium ions to diffuse and migrate.

The monoclinic phase of VO₂ has promising application as a smart window material because it possesses a reversible metal-to-semiconductor transformation with a critical temperature of $68^{\circ }$C. The high critical temperature must be lowered to achieve a possible application. Anion doping has been widely researched as possible doping of VO₂(M) with fluorine is the main option nowadays. However, other halogen elements such as chlorine have not been investigated albeit possessing possible advantages properties. In this work, we report the use of chlorine anion as doping for VO₂(M) to lower its critical temperature and to enhance its thermochromic performance. The synthesis was performed using a facile one-step hydrothermal reduction of vanadium pentoxide by hydrazine at 350–$490^{\circ }$C, using ammonium chloride as the source of the anion. The result showed that the optimum temperature to synthesize Cl-doped VO₂(M) was $490^{\circ }$C. The lowest critical temperature that can be achieved by chlorine-doped VO₂(M) was at $59.9^{\circ }$C. The thermochromic performance of Cl-doped VO₂(M) was improved compared to pristine VO₂(M) nanoparticle. This finding provides a novel use of chlorine-doped VO₂(M) with a facile one-step hydrothermal method to synthesize chlorine-doped VO₂(M) as well as the feasibility of chlorine-doped VO₂(M) as a smart window material.

Porous graphene possesses great potential as an anode material for sodium-ion batteries. Due to the porosity of the graphene, the increase in surface area allows for shorter diffusion length for electrolyte ions. Herein, the porous graphene oxide is created using the breath figure method, and then reduced by chemical, electrochemical, or thermal means. Sodium storage performance of the devised porous graphene is investigated and compared. Reduced graphene oxide shows altered hierarchical porous structures, which are highly dependent on reduction method and conditions. Of the three reduction methods, thermal reduction shows a superior sodium storage performance, yielding a maximum discharge capacity of 187mAh/g and charge capacity of 63mAh/g at a current rate of 50mA/g.