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In the face of multiple failures caused by extreme disasters, the power and communication sides of the distribution network are interdependent in the fault recovery process. To improve the post-disaster recovery efficiency of the distribution network, this paper proposes a coordinated optimization strategy for distribution network reconfiguration and repair, which integrates the power and communication aspects. First, the recovery process is divided into islanding–reconfiguration and dynamic emergency repair. The coupling relationship between power and communication is considered; that is, power failure may cause communication nodes to lose power, and communication failure may affect the effective operation of remote control devices. Based on this, the fault recovery process is optimized with the objective of maximizing load transfer and direct recovery while introducing a stochastic model predictive control method to handle the uncertainty of distributed power generation by rolling optimization of typical scenarios. Finally, the effectiveness of the proposed strategy is verified using an improved IEEE33-node distribution network system. The simulation results show that the proposed method can recover power to the maximum extent and reduce loss while ensuring the safe and stable operation of the distribution system.

Semiconductor Cu2ZnSn(S x Se1-x )4 (CZTSSe) solid solution is considered as a perspective absorber material for solar cells. However, during its synthesis or deposition, any modification in the resulting optical properties is hardly predicted. In this study, experimental and theoretical analyses of CZTSSe bulk crystals and thin films are presented based on Raman scattering and absorption spectroscopies together with compositional and morphological characterizations. CZTSSe bulk and thin films are studied upon a change in the x = S/(S + Se) aspect ratio. The morphological study is focused on surface visualization of the solid solutions, depending on x variation. It has been discovered for the first time that the surface of the bulk CZTSSe crystal with x = 0.35 has pyramid-like structures. The information obtained from the elemental analysis helps to consider the formation of a set of possible intrinsic lattice defects, including vacancies, self-interstitials, antisites, and defect complexes. Due to these results and the experimentally obtained values of the band gap within 1.0-1.37 eV, a deviation from the calculated band gap values is estimated in the range of 1.0-1.5 eV. It is suggested which defects can have an influence on such a band gap change. Also, on comparing the experimental Raman spectra of CZTSSe with the theoretical modeling results, an excellent agreement is obtained for the main Raman bands. The proposed theoretical approach allows to estimate the values of concentration of atoms (S or Se) for CZTSSe solid solution directly from the experimental Raman spectra. Thus, the visualization of morphology and the proposed theoretical approach at various x values will help for a deeper understanding of the CZTSSe structure to develop next-generation solar cells.

Visible-blind ultraviolet-selective photodetection and ultraviolet-visible broad spectral photodetection are two essential functions eagerly pursued in each application area. However, they usually cannot be realized simultaneously in a bare photodetector because their different underlying photoexcitation processes would interfere with each other. In this work, a photodetector integrating the two distinct photodetector characteristics is presented. The device is prepared based on the heterojunction of a large-scale aluminum nitride bulk crystal and monolayer graphene. The visible-blind ultraviolet-selective photodetection and the ultraviolet-visible broad spectral photodetection are separately manifested in the device depending on the bias polarity. Under a negative bias, the device is a visible-blind deep-ultraviolet photodetector, demonstrating a 193/785 nm rejection ratio of over 106 for the photocurrent and a 193/405 nm rejection ratio of over 103 for the signal/noise ratio. Under a positive bias, the device performs as a broad spectral photodetector responding to light from 193 to 785 nm. Systematical characterization reveals that different photodetection manners are the synergistical results of the different photon energies of the incident light, wavelength-dependent penetration depths in AlN, and the different working modes of the device under different bias conditions. This work provides a particular dual-functional photodetector, which is of great significance in terms of both application and device physics.

Strain in two-dimensional (2D) materials has attracted particular attention because of the remarkable modification of electronic and optical properties. However, emergent electromechanical phenomena and hidden mechanisms, such as strain-superlattice-induced topological states or flexoelectricity under strain gradient, remain under debate. Here, using scanning photocurrent microscopy, we observe significant photocurrent enhancement in hybrid vertical junction devices made of strained few-layer graphene and InGaN quantum dots. Optoelectronic response and photoluminescence measurements demonstrate a possible mechanism closely tied to the flexoelectric effect in few-layer graphene, where the strain can induce a lateral built-in electric field and assist the separation of electron-hole pairs. Photocurrent mapping reveals an unprecedentedly ordered hexagonal network, suggesting the potential to create a superlattice by strain engineering. Our work provides insights into optoelectronic phenomena in the presence of strain and paves the way for practical applications associated with strained 2D materials.

Two-dimensional (2D) MoS2 possesses unique optical and electrical properties and has many practical applications in nano-optoelectronics. Raman spectroscopy allows readily identify monolayer of MoS2, but the unambiguous determination of the number of layers in a few-layer structure remains a challenging task. In this work, the modification of frequencies of the most intense bands arising from in-plane and out-of-plane vibrations in the spectra of mono- and few-layer MoS2 crystals is studied experimentally, using the Raman scattering technique, and systematically analyzed theoretically, considering the influence of the interlayer interaction as well as the anharmonic interactions within the layer. A good agreement between experimental spectra and theoretical simulations is demonstrated, which allows to estimate the thickness of few-layer MoS2 and also determine parameters of the interlayer and anharmonic interactions. Possible effects of Fermi resonance in 2D MoS2 and the corresponding frequency shift of fundamental modes are considered. The proposed theoretical approach can be used to analyze Raman spectra, estimate the interlayer interaction, anharmonism, and the number of layers for other 2D layered materials.

A new silicon carbide (SiC) planar-gate insulated-gate bipolar transistor (IGBT) is proposed and comprehensively investigated in this paper. Compared to the traditional SiC planar-gate IGBT, the new IGBT boasts a much stronger injection enhancement effect, which leads to a low on-state voltage (VON) approaching the SiC trench-gate IGBT. The strong injection enhancement effect is obtained by a heavily doped carrier storage layer (CSL), which creates a hole barrier under the p-body to hinder minority carriers from being extracted away through the p-body. A p-shield is located at the bottom of the CSL and coupled to the p-body of the IGBT by an embedded p-MOSFET (metal-oxide-semiconductor field effect transistors). In off-state, the heavily doped CSL is shielded by the p-MOSFET clamped p-shield. Thus, a high breakdown voltage is maintained. At the same time, owing to the planar-gate structure, the proposed IGBT does not suffer the high oxide field that threatens the long-term reliability of the trench-gate IGBT. The turn-off characteristics of the new IGBT are also studied, and the turn-off energy loss (EOFF) is similar to the conventional planar-gate IGBT. Therefore, the new IGBT achieves the benefits of both the conventional planar-gate IGBT and the trench-gate IGBT, i.e., a superior VON-EOFF trade-off and a low oxide field.

Atomically-thin MoS2 is a favorable material for flexible device and nano-optoelectronics application due to unique optical and photoelectrical properties related to the exciton and trion formation. These properties crucially depend on the flake structure, strains and surrounding environment. MoS2 flakes of hexagram (six-pointed star) shape grown by CVD on SiO2/Si are known to be polycrystalline, consisting of six rhomb-like single-crystals with grain boundaries and having uneven residual tensile strains. So, it is an attractive object for studying the influence of polycrystallinity and strains on the exciton and trion emission behavior. In this paper, the micro-photoluminescence (µ-PL) of a bi-layer MoS2 flake of hexagram shape is studied in comparison with a triangular flake of the same thickness and a similar size. The morphology, structural and optical properties are inspected, focusing on the impact of the flake polycrystallinity and residual tensile strains on the exciton and trion PL. It is shown that the hexagram flake possesses special spectral features: an increased exciton PL intensity and the band peak energy shifted towards higher energy at the boundaries between the constituent single-crystals. In contrast, the triangular flake demonstrates rather even spatial distribution of PL. The spectral differences between both the flakes and their parts are explained in terms of tensile strains appearing in MoS2 on SiO2/Si after the post-growth cooling. The tensile strains are shown to redshift all the spectral bands and reduce the A exciton contribution to the spectrum, thus increasing the spectral weight of the B exciton and trion bands.