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In the past decade, molybdenum ditelluride (MoTe2) has received significant attention from the scientific community due to its structural features and unique properties originate from them. In the current review, the properties, various preparation approaches, and versatile applications of MoTe2 are presented. The review provides a brief update on the state of our fundamental understanding of MoTe2 material and also discusses the issues that need to be resolved. To introduce MoTe2, we briefly summarize its structural, optoelectronic, magnetic, and mechanical properties in the beginning. Then, different preparation methods of MoTe2, such as exfoliation, laser treatment, deposition, hydrothermal, microwave, and molecular beam epitaxy, are included. The excellent electrical conductivity, strong optical activity, tunable bandgap, high sensitivity, and impressive stability make it an ideal contender for different applications, including energy storage, catalysis, sensors, solar cells, photodetectors, and transistors. The performance of MoTe2 in these applications is systematically introduced along with mechanistic insights. At the end of the article, the challenges and possible future directions are highlighted to further modify MoTe2 material for the numerous functionalities. Therefore, the availability of different phases and layer structures implies a potential for MoTe2 to lead an era of two‐dimensional materials that began from the exfoliation of graphene. The purpose of this review paper was to provide fundamental information about MoTe2 with an emphasis on its properties, different methods of synthesis, and applications in a variety of fields. The availability of various phase structures with unique optoelectronic properties as well as its modificable layered structure makes MoTe2 material special for next‐generation advanced devices.

In the current investigation, we theoretically explored the halide-based double perovskites Li 2 CuAlX 6 (X = Cl, Br, I), focusing on their structural, optoelectronic, and thermoelectric attributes. The computation of tolerance factor and enthalpy of formation confirms the thermodynamically stable cubic configuration of all the studied compositions. The study of the band structure reveals the direct bandgap nature with the reduction of bandgap value from visible to infrared region upon replacement of halogens in the compositions. It also enhances the absorption coefficient, dielectric function, refractive index, and reflectivity of Li 2 CuAlX 6 (X = Cl, Br, I) highlighting their feasibility for solar cell industry. Employing semiclassical transport theory based BoltzTrap code, the temperature-dependent various transport parameters including electronic and thermal conductivities, Seebeck coefficient, and power factor are computed which enlightened the path of these materials for thermoelectric devices suitable to work at room temperature. Graphical abstract Left sided figure illustrates the atomic configuration within the unit cell of double perovskites Li 2 CuAlX 6 (X = Cl, Br, I). The unit cell adopts a face-centered cubic structure with space group F m 3 ¯ m . According to the crystallographic perspective, the Li atom is situated at interstitial positions, having (0.25, 0.25, 0.25) fractional coordinates, whereas Cu, Al, and X atoms occupy (0, 0, 0), (0.5, 0.5, 0.5), and ( x , 0, 0) positions, respectively. Notably, Li atoms are surrounded by 12 halogen ions, and Cu/Al atoms are surrounded by six halogen ions, giving them coordination numbers of 12 for Cu and 6 for Al. The Li and Cu atoms are represented as green and blue spheres, while Al and X atoms are depicted as grey and red spheres. The figure of merit ( ZT ) versus temperature is presented in right sided figure.

The bandgap tuning potential offered by negative-stiffness lattice structures, characterized by their unique mechanical properties, represents a promising and burgeoning field. The potential of large deformations in lattice structures to transition between stable configurations is explored in this study. This transformation offers a novel method for modifying the frequency range of elastic wave attenuation, simultaneously absorbing energy and effectively generating diverse bandgap ranges. In this paper, an enhanced lattice structure is introduced, building upon the foundation of the normal negative-stiffness lattice structures. The research examined the behavior of the suggested negative-stiffness lattice structures when subjected to uniaxial compression. This included analyzing the dispersion spectra and bandgaps across different states of deformation. It also delved into the effects of geometric parameter changes on bandgap properties. Furthermore, the findings highlight that the normal negative-stiffness lattice structure demonstrates restricted capabilities in attenuating vibrations. In contrast, notable performance improvements are displayed by the improved negative-stiffness lattice structure, featuring distinct energy band structures and variable bandgap ranges in response to differing deformation states. This highlights the feasibility of bandgap tuning through the deformation of negatively stiffened structures. Finally, the overall metamaterial structure is simulated using a unit cell finite element dynamic model, and its vibration transmission properties and frequency response patterns are analyzed. A fresh perspective on the research and design of negative-stiffness lattice structures, particularly focusing on their bandgap tuning capabilities, is offered in this study.

The family of two-dimensional (2D) transition-metal carbides and nitrides, known as MXenes, has attracted substantial attention in science and technology. The electronic structure, optical properties, and bandgap tuning under compressive and tensile strain (CTS) of 2D Sc2CF2 are investigated herein using density functional theory calculations. The results reveal that the bandgap of 2D Sc2CF2 can be tuned by applying CTS. The covalent bonding between the atoms become stronger under compressive strain. To investigate the optical properties, the absorption spectrum and percentage reflectivity of these structures along the x and z directions are calculated using the real and imaginary parts of the dielectric function. Upon applying 2%, 4%, and 6% compressive strain, the number of absorption peaks increases in the visible region along the x direction. These tunable electronic and optical properties of semiconducting 2D Sc2CF2 make it a candidate for the design of optoelectronic devices and in nanodevice applications.

A family of Ruddlesden–Popper (n = 1) layered perovskite-related phases, Az2PbClxBr4−x with composition 0 ≤ x ≤ 4 were obtained using mechanosynthesis. These compounds are isostructural with K2NiF4 and therefore adopt the idealised n = 1 Ruddlesden–Popper structure. A linear variation in unit cell volume as a function of anion average radius is observed. A tunable bandgap is achieved, ranging from 2.81 to 3.43 eV, and the bandgap varies in a second-order polynomial relationship with the halide composition.

HighlightsThe CuaAgm1Bim2In/CuI bilayer films are prepared simultaneously in situ by a one-step low-temperature gas-solid phase diffusion induced elemental reaction without spin coating.A new type of CuaAgm1Bim2In photovoltaic material was originally designed to reduce the bandgap of this class of materials from 2.06 to 1.78 eV by breaking the restriction of double perovskite structure with a ratio of Ag:Bi = 1:1.The power conversion efficiency (PCE) of solar cell with a structure of FTO/TiO2/CuaAgm1Bim2In/CuI/carbon reached 2.76%, which is the highest PCE for CuaAgm1Bim2In absorbers.Lead-free inorganic copper-silver-bismuth-halide materials have attracted more and more attention due to their environmental friendliness, high element abundance, and low cost. Here, we developed a strategy of one-step gas–solid-phase diffusion-induced reaction to fabricate a series of bandgap-tunable CuaAgm1Bim2In/CuI bilayer films due to the atomic diffusion effect for the first time. By designing and regulating the sputtered Cu/Ag/Bi metal film thickness, the bandgap of CuaAgm1Bim2In could be reduced from 2.06 to 1.78 eV. Solar cells with the structure of FTO/TiO2/CuaAgm1Bim2In/CuI/carbon were constructed, yielding a champion power conversion efficiency of 2.76%, which is the highest reported for this class of materials owing to the bandgap reduction and the peculiar bilayer structure. The current work provides a practical path for developing the next generation of efficient, stable, and environmentally friendly photovoltaic materials.

The suitability of halide-based double perovskites for implementation in infrared detectors and thermoelectric devices arises from their inherent environmental stability, non-toxic nature, and demonstrable performance. In the present investigation, our focus centers on an exploration of the structural stability and mechanical attributes intrinsic in Na 2 CuInY 6 (Y = Cl, Br, I) within its cubic phase utilizing DFT. The structural and thermodynamic stability is investigated by computation of tolerance factor and enthalpy of formation. Our methodology encompasses comprehensive calculations of elastic constants based on Born stability criteria that help to understand the mechanical behavior and ductile nature of these compositions. Notably, our scrutiny of the electronic band structure reveals the presence of a direct semiconducting bandgap ranging between 1.30 and 0.36 eV. This distinctive feature holds a pivotal role in facilitating optoelectronic applications because of its pronounced role in absorption within the infrared spectrum. Remarkably, our investigation into the dielectric constant allows us to pinpoint the region of maximal light absorption within the visible spectrum. Lastly, using the BoltzTraP package, we computed the thermoelectric properties of the material and noticed an almost constant value of ZT in the wide range of temperatures highlighting the large range of workability of these compositions for thermoelectric device applications.

Honeycomb structures are widely utilized in engineering due to their light weight, high strength, high stiffness, excellent energy absorption, and outstanding vibration isolation performance. In this study, we propose a novel tuning fork–honeycomb megastructure, which demonstrates excellent tunable vibration isolation capabilities. The geometric configuration of the structure before and after shape memory–induced deformation is described, and a theoretical model for the natural frequency of the initial configuration is established. The vibration isolation performance of the structure is validated through simulations and experiments, and three strategies for tuning its vibrational behavior are proposed. First, by exploiting variable stiffness, shape memory materials are used to achieve a linear shift in the bandgap position. At 75 °C, the starting frequency of the bandgap decreases to 95% of its value at room temperature. Second, based on shape memory programming, the deformed structure exhibits a 20% reduction in the center frequency of the first bandgap and a 47% reduction in the center frequency of the second bandgap compared to the undeformed configuration. Then, by altering the geometry of the tuning fork structure, in–plane deformation is shown to provide superior low–frequency vibration isolation performance compared to out–of–plane deformation. Finally, the design method of programmable mechanical pixel metamaterials is introduced. This method achieves tunable full–band vibration isolation through shape–memory–induced deformation and temperature–induced stiffness variation. It enhances the structural diversity, modularity, and reconfigurability. Moreover, a shape memory tuning fork structure could be combined with any type of cellular structure with excellent vibration isolation performance. It offers a new paradigm for designing structures with adjustable wide–frequency vibration isolation performance.

Hydrogenated two-dimensional (2D) materials have gained significant attention due to their tunable properties, which can be engineered through various functionalization techniques. This review discusses hydrogenated Xenes, a new class of fully hydrogenated mono-elemental 2D materials, including graphane, germanane, silicane, and stanane. Hydrogenation enhances the properties of Xenes, making them transparent, mechanically strong, electrically conductive, and rare. These materials offer a unique combination of characteristics that make them highly desirable for a variety of advanced applications in energy storage, organic electronics, and optoelectronics. Xenes such as silicane and germanane are semiconductors with tunable bandgaps, making them ideal for use in transistors, logic circuits, and sensors. Their electronic and optical properties can be finely adjusted, allowing them to be used in high-performance devices like LEDs, solar cells, and photodetectors. Furthermore, hydrogenated Xenes show potential in applications like batteries, supercapacitors, hydrogen storage, piezoelectricity, and biosensing, owing to their high surface area and versatility. This review also explores the impact of various hydrogenation techniques, including plasma treatment, wet chemical methods, and electrochemical hydrogenation, on the electronic, mechanical, thermal, optical, and magnetic properties of these materials. Advanced characterization techniques, such as X-ray absorption spectroscopy (XANES), have provided valuable insights into the electronic structure and bonding environments of these materials. Finally, the paper highlights the challenges and limitations of hydrogenation, including structural instability and environmental concerns, while discussing the future prospects and advancements needed to harness the full potential of hydrogenated 2D materials. This review serves as a comprehensive resource for researchers aiming to explore the applications of hydrogenated Xenes in next-generation technologies.

We performed first-principles density functional theory (DFT) calculations to numerically investigate the electronic band structures of penta-graphene (PG), a novel two-dimensional carbon material with a pentagonal lattice structure, and its chemically functionalized forms. Specifically, we studied hydrogenated PG (h-PG), fluorinated PG (f-PG), and chlorinated PG (Cl-PG). We used the generalized gradient approximation (GGA) and the hybrid Heyd–Scuseria–Ernzerhof (HSE06) exchange-correlation functional in the DFT-based software VASP to capture electronic properties accurately. Our results indicate that hydrogenation and fluorination increased the indirect bandgap of PG from 3.05 eV to 4.97 eV and 4.81 eV, respectively, thereby effectively transforming PG from a semiconductor to an insulator. In contrast, we found that chlorination closed the bandgap, thus indicating the metallic behavior of Cl-PG. These results highlight the feasibility of tuning the electronic properties of PG through functionalization, offering insight into designing new materials for nanoelectronic applications.