Materials Today Electronics最新文献

Flexible electrochromic (EC) technology has made huge progress in electronic industry for their applications in flexible displays, e-papers, e-curtains etc. The performance of device is the main concern while fabricating a flexible electrochromic device. In this paper, a solid state flexible electrochromic device (flex-ECD) has been demonstrated by combining the excellent EC performance of organic polymer and excellent stability of metal oxides which exhibits fast color switching and excellent stability after bending and twisting it for several times. For the fabrication of device, first Co₃O₄ and WO₃ powders have been synthesised and utilised as dopants in the two electrochromic active materials namely polythiophene (P3HT) and ethyl viologen (EV), respectively. Due to the doping of these nanomaterials the performance of the flex-ECD has been enhanced as measured in terms of coloration efficiency, switching time and stability. Additionally, the device shows color switching in their different wavelength regions between visible and NIR. The flex-ECD shows high stability with a few seconds of switching time and high coloration efficiency of 420 cm²/C. The device was first bent and subsequently twisted for several more times. After bending, the performance has been checked, exhibiting minimal change in switching time at 515 nm and 665 nm without compromising the coloration efficiency much. The device shows excellent stability after bending and twisting moments making it a good design for future wearable electronics.

Magnetic van der Waals (vdW) materials are highly sensitive to their chemical compositions and atomic structures, which presents rich opportunities for synthetic control of vdW ferromagnets. Here, we synthesized the quaternary alloys Cr₂Si_xGe_2-xTe₆ using the flux method and discovered that the Ge:Si source ratio should be designed deliberately higher than the expected in resultant crystals due to the stronger affinity of Si than Ge to be involved in Cr₂Si_xGe_2-xTe₆ reactions. Temperature-dependent magnetization and magnetic hysteresis measurements revealed that as the Si content increases, the Curie temperature decreases while the out-of-plane anisotropy increases monotonically. When x increases from 0 to 2 in Cr₂Si_xGe_2-xTe₆, the out-of-plane saturation fields remain approximately unchanged at ∼0.2 T, while the in-plane saturation fields increase monotonically from 0.5 T to 1.2 T. The distinct behaviors between out-of-plane and in-plane saturation fields arise from the different mechanisms underpinning the two fields – the out-of-plane saturation field is determined by the competition of exchange interaction, magnetic anisotropy, and dipolar interaction, whereas the in-plane saturation field by magnetic anisotropy. Our compositional engineering provides a fundamental understanding of the layered magnetic materials and insightful guidance for the future design of vdW magnets.

The light-emitting efficiencies of blue perovskite light-emitting diodes (PeLEDs) based on quasi-two-dimensional (quasi-2D) halide perovskite emissive layers still lag behind in comparison to their green and red counterparts. The buried interfaces strongly affect the properties of upper solution-processed quasi-2D halide perovskites and the resultant PeLEDs. Herein, it is proposed to passivate the defects of blue quasi-2D perovskites at the buried interfaces by modifying the poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) hole-transport layer (HTL) with 4-guanidinobutyric acid (GBA). The GBA-modified PEDOT:PSS can help to passivate the defects of blue quasi-2D perovskites at the buried interfaces through the interaction between the amine groups of GBA and lead ions and enhance the ratios of halide ions and 4-fluorophenylethylammonium bromide to lead ions. Owing to the reduced halogen vacancies and the passivated defects at the buried interfaces, the blue quasi-2D perovskites prepared on the GBA-modified PEDOT:PSS HTL lead to an increased photoluminescence quantum yield (PLQY) of 60.8 %. The corresponding sky blue PeLEDs achieve a maximum light-emitting quantum efficiency of 9.41 % with an emission peak at 488 nm. This work contributes to enhancing the light-emitting performance of blue PeLEDs through the buried interface passivation point of view.

Pseudocapacitors with oxygen-enriched vacancies have been the state-of-the-art surface chemistry to invoke various intrinsic mechanisms. Nevertheless, the electrochemical behavior of vacancies-induced properties of MoO₃ is still under debate. In this work, we report an oxygen-enriched polymorph of molybdenum trioxide (MoO₃), i.e., H₂MoO₅, which is a thermodynamically unstable phase of MoO₃ with aliovalent oxygen ions (O₂^2- and O₂^-), to achieve a higher amount of pseudocapacitance compared to its thermodynamically stable phase (alpha-MoO₃). Mott-Schottky analysis identified a higher proportion of oxygen vacancies in H₂MoO₅ compared to MoO₃. A symmetric supercapacitor of H₂MoO₅ with PVA/H₂SO₄ displayed a high charge storage of 46.54 F/g at a current density of 0.5 A/g, maintaining a remarkable cycle life of up to 6000 cycles. Furthermore, the oxygen-enriched cell could deliver a high-power density of 470 W/kg at a higher energy density of 22.8472 Wh/kg. The ability to tune oxygen vacancies in metal oxide systems opens a new platform to enhance pseudocapactive character without compromising the energy density.

The emergence of the fascinating non-linear Hall effect intrinsically depends on the non-zero value of the Berry curvature dipole. In this work, we predict that suitable strain engineering in layered van der Waals material phosphorene can give rise to a significantly large Berry curvature dipole. Using symmetry design principles, and a combination of feasible strain and staggered on-site potentials, we show how a substantial Berry curvature dipole may be engineered at the Fermi level. We discover that monolayer phosphorene exhibits the most intense Berry curvature dipole peak near 11.8% strain, which is also a critical point for the topological phase transition in pristine phosphorene. Furthermore, we have shown that the necessary strain value to achieve substantial Berry curvature dipole can be reduced by increasing the number of layers. We have revealed that strain in these van der Waals systems not only alters the magnitude of Berry curvature dipole to a significant value but allows control over its sign. We are hopeful that our predictions will pave way to realize the non-linear Hall effect in such elemental van der Waals systems.

Understanding the charge transport physics is crucial for improving organic field-effect transistors (OFETs) performance. Diverse mobility behaviour has been discovered and numerous theories have been established to explain the nature of charge transport in OFETs. In this review, the theories are divided into three groups, band-like theories, transient localization models, and hopping transport. The relationship between structural properties and intrinsic charge transport physics will be discussed. The fundamental assumptions and theoretical framework of these models will be introduced and their advantages and limits when describing charge transport in OFETs are also discussed based on recent experimental observations. Band-like theory is more applicable to highly-ordered single crystals while hopping models concentrate on disordered materials. Newly developed transient localization theories emphasize the importance of thermal fluctuations, which hopping theories and band-like models fail to include, attributed to weak van der Waals interactions. We integrate and summarize these theories to provide a more sophisticated understanding and more universal descriptions of the charge transport process to guide further developments and potential applications of OFETs.

Intrinsic magnetic two-dimensional (2D) materials with high critical temperature are highly desired in advanced spintronics applications. Via first-principles calculations, we firstly predict that two-dimensional molybdenum carbide (with a chemical formula of Mo${}_2$C₁₂) monolayer is a highly stable antiferromagnetic (AFM) semiconductor with a band gap around 1 eV and a high Néel temperature of 420 K. We then show that the multilayer (Mo${}_2$C₁₂)${}_n$, where $n$ is the number of layers, exhibits interesting electronic and magnetic properties that are sensitively dependent on the number of layers. The stability of the AFM configuration and the energy gap rapidly decrease with the number of layers. When $n\le 5$, (Mo${}_2$C₁₂)${}_n$ remains AFM, while magnetic moments are mainly located on surface Mo atoms, and Mo atoms on top and bottom surfaces have opposite spin polarizations. When $n>5$, the AFM phase is unstable and the material becomes metallic. These layer-tunable properties make (Mo${}_2$C₁₂)${}_n$ potentially useful for various electronics and spintronics applications. As one example, an intriguing (Mo${}_2$C₁₂)${}_5$ based magnetic metal–semiconductor–metal heterojunction is proposed in this work.

Recent experiments evidence the direct observation of spin waves in chromium trihalides and the presence of a gap at the Dirac points of the magnon dispersion in bulk CrI${}_3$. However, the topological origin of this feature remains unclear and its emergence at the 2D limit has not yet been proven experimentally. Herein, we perform a fully self-consistent ab initio analysis to deeply understand magnetic exchange of chromium trihalides in the 2D limit. We compute the orbital dependent magnetic interactions and Curie temperatures under applied biaxial strain. Our results confirm the existence of a gap around the K high-symmetry point in the linear magnon dispersion of CrI${}_3$, which originates as a direct consequence of intralayer Dzyaloshinskii–Moriya (DM) interaction. In addition, our orbital resolved analysis reveals the microscopic mechanisms that can be exploited using strain engineering to increase the strength of the DM interaction and thus control the topological gap width in CrI${}_3$. This paves the way to the further development of this family of materials as building-blocks for topological magnonics at the limit of miniaturization.

There is no wonder that flexible electronics can be considered as a boon for mankind because of its inherent characteristics of portability, stretchability, bendability, and wearability which makes it an ideal vehicle for a plethora of biomedical applications. Flexible electronic device, often integrated for wearable electronics and energy storage electrochromic device, (ESED) is a snowballed research area. This review focuses on the development of flexible ESED where charging and discharging of energy storage device is coupled with decoloration and coloration of an electrochromic device. The strategy behind the integration of energy storage and electrochromic device as a bi-functional device is discussed in length. The essential key parameters for fabrication of flexible ESED and the performance parameters of the flexible ESED have been highlighted. A quantitative analysis of flexible ESED fabricated using different materials has been presented while dwelling into details of possible materials candidates and challenges encountered so far with a possible direction of future research. Enveloping the major research developments in the field of flexible ESED while addressing the possible challenges, a future outlook in the mentioned research thrust have been presented.

Vision is our dominant sense and is also highly desired in artificial systems. In this article, we provide an overview of bio-inspired visual systems that utilize curved image sensors and/or photonic synapses. The use of curved detector geometry ensures clear image sensing abilities with fewer optical elements, which has the potential to lead to miniaturization. Additionally, photonic synapses that integrate light sensing and neuromorphic preprocessing can reduce redundant modules and signal communications. This results in decreased device size and energy consumption. In this review, we begin by summarizing the fabrication processes of curved image sensors, followed by a review of typical bionic eye systems. Next, we discuss the materials and device structures of typical photonic synapses and related imaging systems. We also review the combinations of curved image sensors and photonic synapses. Finally, we summarize the key advantages and challenges of current bio-inspired visual systems.