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The relatively narrow electrochemical steady window and low ionic conductivity are two critical challenges for Li+ -conducting solid polymer electrolytes (SPE). Here, a family of poly-oxalate(POE) structures were prepared as SPE; among them, POEs composed from diols with an odd number of carbons show higher ionic conductivity than those composed from diols with an even number of carbons, and the POE composed from propanediol (C5-POE) has the highest Li+ conductivity. The HOMO (highest occupied molecular orbital) electrons of POE were found located on the terminal units. When using trifluoroacetate as the terminating unit (POE-F), not only does the HOMO become more negative, but also the HOMO electrons shift to the middle oxalate units, improving the antioxidative capability. Furthermore, the interfacial compatibility across the Li-metal/POE-F is also improved by the generation of a LiF-based solid-electrolyte-interlayer(SEI). With the trifluoroacetate-terminated C5-POE (C5-POE-F) as the electrolyte and Li+ -conducting binder in the cathode, the all-solid-state Li/LiNi0.8 Mn0.1 Co0.1 O2 (NMC811) cells showed significantly improved stability than the counterpart with poly-ether, providing a promising candidate for the forthcoming all-solid-state high-voltage Li-metal batteries.

Anti-perovskite type Li2 OHCl was previously studied as a solid-state Li+ conductor. Here, we report that the Li2 OHCl can be electrolyzed at 3.3 V or 4.0 V, with the creation of O2 /HCl gases and the release of 2 equiv. Li+ via two different decomposition routes, depending on the acidity of electrolyte. In the electrolyte with trace acid, the Li2 OHCl is oxidized at a constant voltage of 3.3 V. In neutral electrolyte, the oxidization of Li2 OHCl starts at 4.0 V, but the produced HCl will increase the acidity of electrolyte and lead to a voltage drop to 3.3 V for the electrolysis of Li2 OHCl. The electrolysis of Li2 OHCl delivers a lithium releasing capacity as high as 810 mAh g-1 , with an equivalent Li-deposition or Li-intercalation on anode, making it a promising candidate as a Li reservoir for prelithiation of anode. Using Li2 OHCl as the lithium source, silicon-carbon (Si@C) composite anode can be effectively prelithiated. The full cells composed of LiNi0.8 Mn0.1 Co0.1 O2 (NMC811) cathode and prelithiated Si@C anode exhibited increased capacities with the increment of prelithiation dosages.

Na3V2(PO4)3 (NVP) is one of the most widely studied structures as a cathode of sodium-ion batteries, although the relatively high cost of vanadium and low voltage need to be further improved compar...

Considering the compensation of thermo-optic coefficients (TOC) between GaN-based cavity and TiO2 photonic crystal (PhC) layer, we have theoretically designed a photonic crystal surface emitting laser (PCSEL) with temperature-insensitive wavelength. The structure includes a freestanding GaN membrane with embedded multiple InGaN/GaN quantum well (QW) layer and the top TiO2 PhC layer. The high refractive index (RI) of PhC and the freestanding membrane cavity structure cooperate to enable a stronger field-coupling in PhC, thus fulfill the athermal coupling condition. Interestingly, the wavelength temperature dependence is only 0.0015 nm/°C for such PCSEL with a 82% PhC confinement factor, and its athermal property is proportional to the field confinement factor in TiO2 PhC layer. To illustrate, a general formula has been developed after the investigations of thermo-optic effect and thermal expansion effect.

Despite of the good stability with Li-metal, Li6.75 La3 Zr1.75 Ta0.25 O12 (LLZTO) suffers from large interfacial resistance and severe Li-metal penetration. Herein, a dual layer ceramic electrolyte of Ti-doped LLZTO(Ti-LLZTO)/LLZTO was developed, with the reducible Ti-LLZTO layer contacting Li-metal and the LLZTO layer contacting cathode. The identical crystal structures of Ti-LLZTO and LLZTO enables a seamless contact and a barrierless Li+ transport between them. The densities of Ti-LLZTO pellets are higher than that of LLZTO. With an in situ reduction of Ti-LLZTO by Li-metal, the interfacial wettability was improved and a mixed ion-electron conducting layer was created. Both features help to reduce defects/pores on interface and homogenize the interfacial ionic/electronic flux, facilitating the reduction of interfacial resistance and suppression of dendrites. With the help of Ti-LLZTO layer, long-term stable lithium plating/stripping was reached in an areal capacity of 3.0 mAh cm-2 .

The artificial synthesis of graphdiyne (GDY) in 2010 successfully fills the blank of low temperature preparation of all-carbon allotropes. GDY is an emerging two-dimensional (2D) planar carbon material composed of benzene rings moieties (sp2 carbon atoms), butadiyne (sp carbon atoms) linkers, and well dispersed electron-rich cavities, forming a large π-conjunction structure. GDY has attracted increasing attention in many fields. GDY is the first carbon material with both 2D fast transfer channels for electrons and 3D channels for ions. The 2D electron-rich all-carbon nature endows GDY with considerable conductivity and tunable electronic properties, and the in-plane cavities give it intrinsic selectivity and accessibility for electrochemically active metal ions. In addition, its easy preparation under mild conditions well complements the disadvantages of the traditional sp2-hybridized carbon materials (carbon nanotubes, graphene, and graphite) in the highly efficient synthesis and processing for potential electrochemical applications. As an all-carbon material, the unique advantages of GDY in both structure and preparation match well the urgent demands in key materials for solving many challenging problems in recent electrochemical areas and beyond. During the last decade since the first preparation of GDY, it has already achieved much enlightening and creative progress in both fundamental scientific research and forward-looking applications. This Account is intended not to summarize all this progress in preparation and applications but to outline some newly reported interesting phenomena in both high-quality preparation and electrochemical applications. This Account mainly discusses the recent progress in electrochemical applications: (i) constructing new concepts and new functions in electrochemical interfaces for realizing highly active electrochemical catalysts in the fields of water splitting and oxygen reduction reaction and (ii) building a highly stable conductive network and electrochemical interface for reversible energy storage. In the field of electrochemical catalysis, based on current studies of structural advantages and superior performance, atomic catalysis with metal atoms anchored in GDY is encouraging, owing to the desirable immobilizing capability of electron-rich dialkyne cavities toward metal atoms and corresponding electron transfer. For high-energy batteries, the in situ growth of the all-carbon GDY on the various battery electrodes shows great promise for solving key practical problems (safety, long lifespan, high power), which are ascribed to weak interfacial stability. In addition, the perspective application of GDY to broader interfacial modifications is described, bringing new choices for solving the interfacial challenges in various energy storage devices.

Sulfur covalently bonded to porous graphitic carbon (CB–S@PGC) as an anode for lithium-ion capacitors is shown to offer an ultrawide operating potential window of 4 V. When coupled with activated carbon as a cathode, the CB–S@PGC electrode exhibits a markedly high specific capacitance (412 F g−1 at 0.2 A g−1) and superiorly high capacity retention. And CB–S@PGC//lithium cobalt oxide cells exhibit high power and energy densities (e.g., a power density of 1665 W kg−1 is obtained at an energy density of 411 W h kg−1).

We report here an optically pumped deep UV edge emitting laser with AlGaN multiple quantum wells (MQWs) active region grown on AlN substrate by low pressure organometallic vapor phase epitaxy (LP-OMVPE) in a high-temperature reactor. The 21 period Al0.53Ga0.47N/Al0.7Ga0.3N MQWs laser structure was optically pumped using 193 nm deep UV excimer laser source. A laser peak was achieved from the cleaved facets at 280.3 nm with linewidth of 0.08 nm at room temperature with threshold power density of 320 kW/cm2. The emission is completely TE polarized and the side mode suppression ratio (SMSR) is measured to be around 14 dB at 450 kW/cm2.

We report the intrinsic linewidth in a photonic crystal surface-emitting laser diode. An intrinsic linewidth of 330 kHz was obtained without any optical feedback, one order smaller than the value of DFB lasers. The impact of cavity feedback on linewidth was also characterized.

Photonic crystal slabs are the state of the art in studies for the light confinement, optical wave modulating and guiding, as well as nonlinear optical response. Previous studies have shown abundant real-world implementations of photonic crystals in planar optics, metamaterials, sensors, and lasers. Here, we report a novel full 2{\pi} phase control method in the reflected light beam over the interaction with a photonic crystal resonant mode, verified by the temporal coupled-mode analysis and S-parameter simulations. Enhanced by the asymmetric coupling with the output ports, the 2{\pi} phase shift can be achieved with the silicon photonics platforms such as Silicon-on-Silica and Silicon-on-Insulator heterostructures. Such photonic crystal phase control method provides a general guide in the design of phase-shift metamaterials, suggesting a wide range of applications in the field of sensing, spatial light modulation, and beam steering., Comment: Including supplementary

Photonic crystal lasers can be realized either based on photonic bandgap defect mode or defect-free bandedge mode, while the bandgap is not essential for the latter. We review here defect-free bandedge mode based photonic crystal surface-emitting lasers (PCSELs) for on-chip integration. We first discuss ultra-thin membrane reflector vertical-cavity surface-emitting lasers (MR-VCSELs), where single layer photonic crystal slabs can be designed as a broadband membrane reflector. Later, we discuss another type of defect-free PCSELs where the lasing cavity is formed based on evanescent coupling of gain medium with the photonic crystal bandedge mode near bandedge. Cavity designs were carried out for the optimal modal overlap and high confinement factors. Lateral cavity size scaling was also investigated both theoretically and experimentally in PCSELs. Buried tunnel junction based InGaAsP quantum well heterostructures were also designed and incorporated into electrically injected PCSELs. Finally, discussions are given toward energy efficient lasers.

Sequential media G5 series (Vitrolife) and single-step medium Continuous Single Culture Complete (CSC-C) (Irvine Scientific) are two different culture media. We want to examine difference between culturing effects of the two media. To compare the fertilization and early embryo development, a prospective randomized controlled trial with sibling oocytes in infertile patients, aged ≤ 45 years with ≥ 8 oocytes (226 cycles) was conducted. Each half of the retrieved oocytes from the same patient were randomly allocated to two culture media separately. The remaining fresh cycles were randomly assigned to two culture media during the same period (179 cycles). We compared the clinical outcomes based on the total fresh ET cycles in this periods, in which the transferred embryos were only from one culture medium. Embryo outcomes: 226 cycles, included 176 IVF and 50 ICSI cycles, were analyzed, which correspond to 3518 inseminated or micro-injected oocytes. Clinical outcomes: 71 (CSC-C) and 71 (G5 series) fresh ET cycles were compared. There were no significant differences in clinical outcomes and general fertilization rate. However, the fertilization rate was superior in the CSC-C when compared with G5 in ICSI cycles (76.51% vs. 67.25%, P = 0.008). In addition, the compacted embryo development rate was significantly higher in CSC-C on day 3. The cycles that had compacted embryos on day 3 demonstrated better outcomes both in embryos as well as clinically. CSC-C had higher fertilization rates than G5 series in ICSI cycles. In addition, the compaction rates of day 3 embryos were significantly higher in CSC-C.

Epitaxial regrowth is investigated as a method of PCSEL fabrication and is compared to non-regrowth methods. The influence of regrowth to photonic crystal morphology is explored and optically pumped and electrically injected devices are demonstrated.

Static and dynamic characteristics of quantum well lasers are simulated and their dependence on volume of active region and quality factor of cavity are obtained using a three-rate equation model. Energy cost of 0.06 fJ/bit is obtained from a proposed nanobeam cavity Photonic crystal laser.

We propose a direction finding method for multiple-input multiple-output (MIMO) radar by using sparse sensing in low computational cost. Since the targets are sparsely distributed in the space, we employ the compressive sensing technique to reduce the sampling rate. Based on the compressive sensing, we utilize the convex combination to approximate the real target parameters in MIMO radar. We formulate an optimization problem for sparse vector recovery and off-grid mismatch estimation, which involves four set of variables. We employ the alternating direction method of multipliers approach to fast solve this optimization problem. In each iteration of sparse recovery, four subproblems are alternately optimized over only one of four set of parameters where each subproblem has a closed-form solution. With the recovered sparse vector and the estimated off-grid mismatch, we develop a grid adjustment method to accurately resolve the directions of targets by iteratively deleting the redundant grid points. Numerical simulations indicate that the proposed method is able to achieve accurate signal recovery, improved estimation accuracy and reduced computational cost.

Sodium alginate (SA) solution with high quality fraction was prepared by NaOH/urea, NaOH/thiourea/urea, NaOH/thiourea and LiOH/urea at low temperature. The results showed that we got 5.5 wt% SA solution by using 5.5 wt% LiOH/20 wt% urea. The viscosity of the solution was 62.44 Pa·s, which had declined by 64% compared to that of 5 wt% SA solution (176.12 Pa·s). The difference from the traditional low temperature dissolution principle is that the urea is mainly wrapped on the SA surface by the interaction between the OH− in LiOH through the ether bond ( O ) and the π bond in the SA instead of the -OH in the SA. Only the crystallization peak of urea appeared in the XRD spectrum. It indicated that urea was successfully wrapped on the surface of SA to form urea-LiOH-SA inclusion complex. The 23Na NMR showed that the interaction between Na+ and other ions or molecules around it increased at low temperature. Breaking strength of regenerated CA was 2.44 cN/dtex, which rose by about 21.39% compared to that of CA fiber (2.01 cN/dtex). The “groove” on the surface of regenerated fiber is denser and the section is more loosely compared with those of CA fiber.

We report here the lateral cavity size scaling and confinement effects on the lasing performance in defect-free photonic crystal surface-emitting lasers (PCSEL) on silicon substrates. Hybrid PCSELs with different lateral cavity sizes and different lateral confinement geometries have been fabricated using transfer printing technology and controlled selective etching. The measured lasing properties show a strong dependence on the lateral cavity size below 100 μm. In particular, the finite lateral dimension significantly affects the laser threshold and side mode suppression ratio (SMSR) of the PCSEL devices. On the other hand, by controlling the lateral confinement using vertical etching, a reduction of the laser threshold is observed. The experimental results agree well with theoretical predictions. The work presented here can lead to ultra-compact PCSELs for on-chip integration with excellent energy efficiency.

Improving the utilization ratio of sunlight is a key factor for the development of solar cell. In this paper, a quasi uniform cone-array-like microstructure was directly fabricated on monocrystal silicon surface in atmosphere by using an alternative femtosecond laser texturing technique. The fabricated cone array like microstructure has a spike depth of up to 8 μm and is able to substantially reduce light reflection due to the effective optical coupling between the incident light with the cone array like microstructure. Compare to planar silicon wafer, the relative reflectance of the cone array structure has been decreased to less than 9% in the measured wavelength range from 400 to 1000 nm. This may be a promising method for the optimal fabrication of surface-microstructure photovoltaic material, such as solar cell, infrared sensor, etc.

In this paper, the problem of direction-of-arrival (DOA) estimation for monostatic multiple-input multiple-output (MIMO) radar with gain-phase errors is addressed, by using a sparse DOA estimation algorithm with fourth-order cumulants (FOC) based error matrix estimation. Useful cumulants are designed and extracted to estimate the gain and the phase errors in the transmit array and the receive array, thus a reliable error matrix is obtained. Then the proposed algorithm reduces the gain-phase error matrix to a low dimensional one. Finally, with the updated gain-phase error matrix, the FOC-based reweighted sparse representation framework is introduced to achieve accurate DOA estimation. Thanks to the fourth-order cumulants based gain-phase error matrix estimation, and the reweighted sparse representation framework, the proposed algorithm performs well for both white and colored Gaussian noises, and provides higher angular resolution and better angle estimation performance than reduced-dimension MUSIC (RD-MUSIC), adaptive sparse representation (adaptive-SR) and ESPRIT-based algorithms. Simulation results verify the effectiveness and advantages of the proposed method.

The DOA estimation problem for monostatic MIMO radar is considered.A reweighted smoothed l0-norm minimization framework with a reweighted continuous function is designed for DOA estimation.The proposed method is about two orders of magnitude faster than conventional l1-norm minimization based DOA algorithms.The proposed method provides better angle estimation performance than l1-SVD, reweighted l1-SVD, RV l1-SRACV, RD-Capon and RD-ESPRIT algorithms. In this paper, a reweighted smoothed l0-norm algorithm is proposed for direction-of-arrival (DOA) estimation in monostatic multiple-input multiple-output (MIMO) radar. The proposed method firstly performs the vectorization operation on the covariance matrix, which is calculated from the latest received data matrix obtained by a reduced dimensional transformation. Then a weighted matrix is introduced to transform the covariance estimation errors into a Gaussian white vector, and the proposed method further constructs the other reweighted vector to enhance sparse solution. Finally, a reweighted smoothed l0-norm minimization framework with a reweighted continuous function is designed, based on which the sparse solution is obtained by using a decreasing parameter sequence and the steepest ascent algorithm. Consequently, DOA estimation is accomplished by searching the spectrum of the solution. Compared with the conventional l1-norm minimization based methods, the proposed reweighted smoothed l0-norm algorithm significantly reduces the computation time of DOA estimation. The proposed method is about two orders of magnitude faster than the l1-SVD, reweighted l1-SVD and RV l1-SRACV algorithms. Meanwhile, it provides higher spatial angular resolution and better angle estimation performance. Simulation results are used to verify the effectiveness and advantages of the proposed method.

Modulation of carrier density in graphene has been demonstrated on single-crystalline or polymer ferroelectrics as gating dielectric. However, its tuning from p-type to n-type in air at room temperature has not yet been reported. In this paper, such a tuning is realized on polycrystalline PbZr 0.52 Ti 0.48 O 3 (PZT) ceramic under polarization field in the range of – 22.5 kV/cm to 22.5 kV/cm through the construction of a “graphene/PZT + suspended graphene” network film. The maximum hole and electron density of graphene in our fabricated Hall bar device are measured to be 6.3 × 10 13 cm −2 and 1.7 × 10 13 cm −2 respectively. There exhibit certain features in graphene's Raman spectrums corresponding to its transition from p-type to n-type with relationship to the PZT surface morphology and the contact status between graphene and PZT surface. At last, an in-plane graphene PN junction is demonstrated on PZT ceramic as well.

Potassium has as rich an abundance as sodium in the earth, but the development of a K-ion battery is lagging behind because of the higher mass and larger ionic size of K+ than that of Li+ and Na+, which makes it difficult to identify a high-voltage and high-capacity intercalation cathode host. Here we propose a cyanoperovskite KxMnFe(CN)6 (0 ≤ x ≤ 2) as a potassium cathode: high-spin MnIII/MnII and low-spin FeIII/FeII couples have similar energies and exhibit two close plateaus centered at 3.6 V; two active K+ per formula unit enable a theoretical specific capacity of 156 mAh g–1; Mn and Fe are the two most-desired transition metals for electrodes because they are cheap and environmental friendly. As a powder prepared by an inexpensive precipitation method, the cathode delivers a specific capacity of 142 mAh g–1. The observed voltage, capacity, and its low cost make it competitive in large-scale electricity storage applications.

The practical use of lithium-sulfur batteries for the next-generation energy storage, especially the automobiles, was hindered by low electronic conductivity of sulfur and the resulting poor rate capabilities. Here, we report a sulfur-carbon composite by confining S into a graphene sandwiched in mesoporous carbon nanosheets with a two-dimensional ultrathin morphology, suitable mesopore size and large pore volume, and excellent electronic conductivity. Serving as cathode material for a Li-S battery, the elaborately designed S/C composite leads to "kinetically stable" transmissions of Li ions and electrons, triggering a stable electrochemistry and a record-breaking rate performance. In this way, the S/C composite has been proved a promising cathode material for high-rate Li-S batteries targeted at automobile storage.

Three-dimensionally confined semiconductor quantum dots have emerged to be a versatile material system with unique physical properties for a wide range of device applications. With the advances in nanotechnology and material growth techniques for both epitaxial and colloidal quantum dots, recently the research has been shifted largely towards quantum dot based devices for practical applications. In this short review, we have tried to assemble a selection of recent advances in the areas of quantum dots for computing and communications, solid state lighting, photovoltaics, and biomedical applications that highlight the state of the art.

We report optically pumped 1 μm low threshold GaAs photonic crystal surface emitting lasers. The GaAs photonic crystal is etched on 3-period InGaAs/AlGaAs MQW heterostructure. A laser peak is achieved at 1,006 nm with a linewidth of 0.6 nm at 5 kW/cm2 threshold power density.

Silicon-integrated laser sources are of great interest for chip-level optical interconnects and significant efforts have been devoted to their development during recent years, with the most promising approaches being due to heterogeneous integration of III-V semiconductor based active material on silicon substrate. We have previously demonstrated optically pumped ultra-compact InP-based surface-emitting membrane lasers on silicon using transfer print technology. For electrically pumped devices, a uniform and efficient current injection in ultrathin device structures with laterally displaced electrodes is inherently difficult to achieve. The current feeding and spreading layers are heavily restricted in thickness which by traditional methods would lead to uneven carrier injection, enhanced optical absorption and excessive Joule heating, in the end compromising the device performance. Here we investigate a buried tunnel junction (BTJ) current injection scheme using selective etching and epitaxial regrowth for lateral confinement. In this approach the current injection layers are almost exclusively n-type which leads to reduced optical absorption and increased electrical conductivity, and the TJ heterostructure ensures an even injection profile also for large-area devices. Membrane-type BTJ light-emitting diodes and photonic crystal surface emitting laser structures are demonstrated with low series resistance, efficient carrier confinement and laterally uniform current injection over large area.

Photonic-crystal surface emitting lasers (PCSELs) exhibit several unique features compared to conventional vertical cavity surface-emitting lasers (VCSEL) including scalability, high power, and high beam quality. They are promising candidates in power-demanding applications such as free-space sensing. Motivated by the experimental advances, there have been significant efforts in developing the simulation tools for PCSELs. In particular, a coupled mode theory (CWT) model for PCSEL was developed, which provides important insights into the operating mechanisms. However, CWT makes several uncontrolled approximations such as a small number of waveguide modes as the basis, which is difficult to justify since the index contrast in PCSELs can be quite large. Here we show that PCSELs, especially its lasing threshold, can be simulated from first-principles by using rigorous coupled-wave analysis (RCWA). Traditionally, RCWA has been widely used to simulate the transmission or reflection of such structures, where the frequency is real. Here, we use RCWA to calculate the scattering matrix (S-matrix) of PCSELs on the complex frequency plane. This approach builds upon the concepts from steady-state ab initio laser theory (SALT). On the complex frequency plane, the poles of the S-matrix correspond to various resonances of the structure, including Fabry-Perot resonances and the guided resonances. We gradually increase the material gain in the PCSEL, and the threshold is retrieved as the gain value for which the first pole crosses the real axis. Other important characteristics such as the quality factor of each mode and the power efficiency of the laser can be computed as well.

Photonic crystal lasers can be realized either based on photonic bandgap defect-mode or defect-free bandedge mode, while the bandgap is not essential for the latter. In this chapter, we introduce types of photonic crystal bandedge mode-based surface-emitting membrane lasers for on-chip integration. We first discuss membrane reflector vertical-cavity surface-emitting lasers based on single-layer photonic crystal membrane reflector with broadband reflections. We will discuss the cavity principles, design, and characteristics. Then, we will discuss on-chip photonic crystal surface-emitting lasers (PCSELs) based on photonic crystal bandedge mode near Γ-point. Cavity designs were carried out for the optimal modal overlap and high confinement factors. Lateral cavity size scaling was also investigated both theoretically and experimentally in PCSELs. Buried tunnel junction-based InGaAsP quantum well heterostructures were also designed and incorporated into electrically injected PCSELs. Finally discussions are given toward energy efficient lasers.

The cross-linked polyacrylamide (PAM)/calcium alginate (CA)/polyethylene glycol (PEG) phase change aerogel (PCA) with double network (DN) structure was prepared by emulsion polymerization for thermal energy management. The PCA retained the original porous structure of the aerogel combined with high phase change latent heat and achieved the dual functions of phase change material (PCM) and aerogel. The analysis of BET revealed that porosity and BET specific surface area of PCA were 71.9% and 230 m2/g, respectively. The pore size distribution of PCA was between 1.73 and 9.13 nm. The melting enthalpy and crystallization enthalpy of the PCA based on differential scanning calorimetry (DSC) results were 91.5 J/g at 37.9 °C and 89.8 J/g at 37.3 °C, respectively. The PCA exhibited good thermal reliability and stability based on the thermogravimetric analysis (TGA) curve and the thermal cycle test.

NASICON (Na+ super ionic conductor) structures of NaxMV(PO4)3 (M = Mn, Fe, Ni) were prepared, characterized by aberration-corrected STEM and synchrotron radiation, and demonstrated to be durable cathode materials for rechargeable sodium-ion batteries. In Na4MnV(PO4)3, two redox couples of Mn3+/Mn2+ and V4+/V3+ are accessed with two voltage plateaus located at 3.6 and 3.3 V and a capacity of 101 mAh g–1 at 1 C. Furthermore, the Na4MnV(PO4)3 cathode delivers a high initial efficiency of 97%, long durability over 1000 cycles, and good rate performance to 10 C. The robust framework structure and stable electrochemical performance makes it a reliable cathode materials for sodium-ion batteries.

The TiN-S composite cathode exhibits superior performance because of higher electrical conductivity and the capture of the soluble intermediate species of the electrode reactions by 2-5 nm mesopores and strong N-S surface bonding.

In this paper, a covariance vector sparsity-aware DOA estimation method is proposed for monostatic multiple-input multiple-output (MIMO) radar with unknown mutual coupling. The new method firstly utilizes the banded symmetric Toeplitz structure of the mutual coupling matrix (MCM) in both of the transmit and receive arrays to eliminate the unknown mutual coupling. Then a sparse representation framework of the array covariance vector is formulated for obtaining the coarse DOA estimation. Finally, a refined maximum likelihood estimation procedure is introduced to estimate the DOA based on the recovered result. Compared with conventional algorithms, the proposed method provides higher angular resolution and better angle estimation performance. Furthermore, the computational complexity of the proposed method is reasonable, because it only involves single measurement vector (SMV) problem and does not require a dense discretized sampling grid for the recovered procedure. Simulation results are used to verify the effectiveness and advantages of the proposed method. HighlightsThe DOA estimation problem for monostatic MIMO radar with unknown mutual coupling is considered.A sparse representation framework of covariance vector is proposed for the coarse DOA estimation.A maximum likelihood estimation procedure is exploited for the accurate DOA estimation.The proposed method provides better performance than both l1-SVD and ESPRIT-Like algorithms.

In the present research, epitaxial regrowth by molecular beam epitaxy (MBE) is investigated as a fabrication process for void-semiconductor photonic crystal (PhC) surface emitting lasers (PCSELs). The PhC is patterned by electron beam lithography (EBL) and inductively coupled plasma (ICP) etch and is subsequently regrown by molecular beam epitaxy to embed a series of voids in bulk semiconductor. Experiments are conducted to investigate the effects of regrowth on air-hole morphology. The resulting voids have a distinct teardrop shape with the radius and depth of the etched hole playing a very critical role in the final regrown void’s dimensions. We demonstrate that specific hole diameters can encourage deposition to the bottom of the voids or to their sidewalls, allowing us to engineer the shape of the void more precisely as is required by the PCSEL design. A 980 nm InGaAs quantum well laser structure is optimized for low threshold lasing at the design wavelength and full device structures are patterned and regrown. An optically pumped PCSEL is demonstrated from this process.

The cross-linked poly (N-methylol acrylamide)/polyethylene glycol (PN-MA/PEG) with an interpenetrating polymer network (IPN) was prepared by emulsion polymerization as composite phase change material (CPCM). N, N′-methylene bisacrylamide (MBA) was used for crosslinking agent. The prepared CPCM was characterized by Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), thermal cycle test, Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). FT-IR results stated that there is no chemical interaction between PEG and PN-MA. XRD results indicated that the introduction of PN-MA did not change the crystal type of PEG. PEG still exhibits crystallization behavior under the constraints of cross-linked PN-MA. The DSC results indicated that CPCM melts at 26.24 °C with a latent heat of 106.5 J/g and solidifies at 32.56 °C with a latent heat of 104.9 J/g. The TGA results indicated that the CPCM has good thermal stability and is suitable for thermal energy storage application. The results of thermal cycle test indicated that the macroscopic morphology and latent heat of CPCM were almost unchanged after 40 thermal cycles. SEM and TEM results indicated that the microscopic morphology of CPCM was spherical and the particle size distribution was around 145 nm.

Monolayer WS 2 shows highly directional emission when transferred onto heterostructure photonic crystal cavities based on the band edge mode above the light cone.

No single polymer or liquid electrolyte has a large enough energy gap between the empty and occupied electronic states for both dendrite-free plating of a lithium-metal anode and a Li+ extraction from an oxide host cathode without electrolyte oxidation in a high-voltage cell during the charge process. Therefore, a double-layer polymer electrolyte is investigated, in which one polymer provides dendrite-free plating of a Li-metal anode and the other allows a Li+ extraction from an oxide host cathode without oxidation of the electrolyte in a 4 V cell over a stable charge/discharge cycling at 65 °C; a poly(ethylene oxide) polymer contacts the lithium-metal anode and a poly(N-methyl-malonic amide) contacts the cathode. All interfaces of the flexible, plastic electrolyte remain stable with no visible reduction of the Li+ conductivity on crossing the polymer/polymer interface.

We report progresses made in continued scaling in laser cavity and gain medium towards potential few photon sources. Performance of an optically pumped continuous wave room temperature operation monolayer WS 2 laser will be discussed, based on a heterostructure photonic crystal cavity for efficient light extraction and surface-emission.

Surface antireflection micro and nanostructures, normally formed by conventional reactive ion etching, offer advantages in photovoltaic and optoelectronic applications, including wider spectral wavelength ranges and acceptance angles. One challenge in incorporating these structures into devices is that optimal optical properties do not always translate into electrical performance due to surface damage, which significantly increases surface recombination. Here, we present a simple approach for fabricating antireflection structures, with self-passivated amorphous Ge (α-Ge) surfaces, on single crystalline Ge (c-Ge) surface using the inverse metal-assisted chemical etching technology (I-MacEtch). Vertical Schottky Ge photodiodes fabricated with surface structures involving arrays of pyramids or periodic nano-indentations show clear improvements not only in responsivity, due to enhanced optical absorption, but also in dark current. The dark current reduction is attributed to the Schottky barrier height increase and self-passivation effect of the i-MacEtch induced α-Ge layer formed on top of the c-Ge surface. The results demonstrated in this work show that MacEtch can be a viable technology for advanced light trapping and surface engineering in Ge and other semiconductor based optoelectronic devices.

β-Ga2O3 is an emerging wide band-gap semiconductor that holds great promise for next generation power electronics and optoelectronics. β-Ga2O3 based ultraviolet photodetectors have been the subject of active research for the last few years. However, no micro and nanostructure surface texturing has been demonstrated for efficient light management in β-Ga2O3 optoelectronic applications yet. We hereby present nanoscale groove textured β-Ga2O3 metal-semiconductor-metal photodiodes, enabled by the unique metal-assisted chemical etching (MacEtch) method at room temperature in liquid. Although the textured surface stoichiometry shows ∼10% oxygen deficiency which results in a reduced Schottky barrier height and increased dark current, clear enhancement of the responsivity is demonstrated, compared to the planar untreated surface. The realization of MacEtch's applicability to β-Ga2O3 opens the door for producing more sophisticated device structures for this material, without resorting to conventional dry etch and potential damage. Published version

We report here an electrically pumped hybrid photonic crystal surface emitting laser (PCSELs) on silicon. The laser cavity consists of a transferred InGaAsP multi-quantum well (MQW) heterostructure membrane, printed on a single layer silicon photonic crystal (Si-PC) cavity. A buried tunnel-junction (BTJ) has been employed in the MQW structure for efficiency charge injection. Single mode emitted spectrum was achieved at 1504 nm for a large area laser in the continuous-wave (c.w.) mode under room temperature operation.

Recently, solution-processed hybrid halide perovskite has emerged as promising materials for advanced optoelectronic devices such as photovoltaics, photodetectors, light emitting diodes and lasers. In the mean time, all-dielectric metasurfaces with high-index materials have attracted attention due to their low-loss and high-efficient optical resonances. Because of its tunable by composition band gap in the visible frequencies, organolead halide perovskite could serve as a powerful platform for realizing high-index, low-loss metasurfaces. However, direct patterning of perovskite by lithography-based technique is not feasible due to material instability under moisture. Here we report novel organolead halide perovskite metasurfaces created by the cost-effective thermal nanoimprint technology. The nanoimprinted perovskite metasurface showed improved surface morphology and enhanced optical absorption properties. Significantly enhanced optical emission with an eight-fold enhancement in photoluminescence (PL) intensity was observed under room temperature. Temperature-dependent PL of perovskite nanograting metasurface was also investigated. Based on our results, we believe that thermal nanoimprint is a simple and cost-effective technique to fabricate perovskite-based metasurfaces, which could have broad impact on optoelectronic and photonic applications.

Heterogeneous crystalline semiconductor nanomembrane (NM) integration is investigated for single-layer and double-layer Silicon (Si) NM photonics, III-V/Si NM lasers, and graphene/Si NM total absorption devices. Both homogeneous and heterogeneous integration are realized by the versatile transfer printing technique. The performance of these integrated membrane devices shows, not only intact optical and electrical characteristics as their bulk counterparts, but also the unique light and matter interactions, such as Fano resonance, slow light, and critical coupling in photonic crystal cavities. Such a heterogeneous integration approach offers tremendous practical application potentials on unconventional, Si CMOS compatible, and high performance optoelectronic systems.

Reduced graphene oxides loaded with tin-antimony alloy (RGO-SnSb) nanocomposites were synthesized through a hydrothermal reaction and the subsequent thermal reduction treatments. Transmission electron microscope images confirm that SnSb nanoparticles with an average size of about 20-30 nm are uniformly dispersed on the RGO surfaces. When they were used as anodes for rechargeable sodium (Na)-ion batteries, these as-synthesized RGO-SnSb nanocomposite anodes delivered a high initial reversible capacity of 407 mAh g(-1), stable cyclic retention for more than 80 cycles and excellent cycle stability at ultra high charge/discharge rates up to 30C. The significantly improved performance of the synthesized RGO-SnSb nanocomposites as Na-ion battery anodes can be attributed to the synergetic effects of RGO-based flexible framework and the nanoscale dimension of the SnSb alloy particles (30 nm). Nanosized intermetallic SnSb compounds can exhibit improved structural stability and conductivity during charge and discharge reactions compared to the corresponding individuals (Sn and Sb particles). In the meantime, RGO sheets can tightly anchor SnSb alloy particles on the surfaces, which can not only effectively suppress the agglomeration of SnSb particles but also maintain excellent electronic conduction. Furthermore, the mechanical flexibility of the RGO phase can accommodate the volume expansion and contraction of SnSb particles during the prolonged cycling, therefore, improve the electrode integrity mechanically and electronically. All of these contribute to the electrochemical performance improvements of the RGO-SnSb nanocomposite-based electrodes in rechargeable Na-ion batteries.