Advances in the Application of Perovskite Materials

Nowadays, the soar of photovoltaic performance of perovskite solar cells has set off a fever in the study of metal halide perovskite materials. The excellent optoelectronic properties and defect tolerance feature allow metal halide perovskite to be employed in a wide variety of applications. This article provides a holistic review over the current progress and future prospects of metal halide perovskite materials in representative promising applications, including traditional optoelectronic devices(solar cells, light-emitting diodes, photodetectors, lasers), and cutting-edge technologies in terms of neuromorphic devices(artificial synapses and memristors) and pressure-induced emission. This review highlights the fundamentals, the current progress and the remaining challenges for each application, aiming to provide a comprehensive overview of the development status and a navigation of future research for metal halide perovskite materials and devices.

低品质/低活性原材料在现代混凝土中的应用技术

针对低品质/低活性原材料难以利用的实际情况,打破了传统使用高品质/高活性原材料制备现代混凝土的限制,研发了利用低品质/低活性原材料制备现代混凝土的新工艺和新技术。通过实验室研究和现场试验,提出一整套具有针对性的技术方案如高性能混凝土、大体积混凝土、防腐蚀混凝土、超低强度充填混凝土,并在国内外多个重点工程成功应用。

Performance analysis and comparison of PoW,PoS and DAG based blockchains

In the blockchain,the consensus mechanism plays a key role in maintaining the security and legitimation of contents recorded in the blocks.Various blockchain consensus mechanisms have been proposed.However,there is no technical analysis and comparison as a guideline to determine which type of consensus mechanism should be adopted in a specific scenario/application.To this end,this work investigates three mainstream consensus mechanisms in the blockchain,namely,Proof of Work(PoW),Proof of Stake(PoS),and Direct Acyclic Graph(DAG),and identifies their performances in terms of the average time to generate a new block,the confirmation delay,the Transaction Per Second(TPS)and the confirmation failure probability.The results show that the consensus process is affected by both network resource(computation power/coin age,buffer size)and network load conditions.In addition,it shows that PoW and PoS are more sensitive to the change of network resource while DAG is more sensitive to network load conditions.

Genome wide association study identifies SNPs associated with fatty acid composition in Chinese Wagyu cattle

Background: Fatty acids are important traits that affect meat quality and nutritive values in beef cattle. Detection of genetic variants for fatty acid composition can help to elucidate the genetic mechanism underpinning these traits and promote the improvement of fatty acid profiles. In this study, we performed a genome-wide association study(GWAS) on fatty acid composition using high-density single nucleotide polymorphism(SNP) arrays in Chinese Wagyu cattle.Results: In total, we detected 15 and 8 significant genome-wide SNPs for individual fatty acids and fatty acid groups in Chinese Wagyu cattle, respectively. Also, we identified nine candidate genes based on 100 kb regions around associated SNPs. Four SNPs significantly associated with C14:1 cis-9 were embedded with stearoyl-CoA desaturase(SCD), while three SNPs in total were identified for C22:6 n-3 within Phospholipid scramblase family member 5(PLSCR5), Cytoplasmic linker associated protein 1(CLASP1), and Chymosin(CYM). Notably, we found the top candidate SNP within SCD can explain ~ 7.37% of phenotypic variance for C14:1 cis-9.Moreover, we detected several blocks with high LD in the 100 kb region around SCD. In addition, we found three significant SNPs within a 100 kb region showing pleiotropic effects related to multiple FA groups(PUFA,n-6, and PUFA/SFA), which contains BAI1 associated protein 2 like 2(BAIAP2 L2), MAF bZIP transcription factor F(MAFF),and transmembrane protein 184 B(TMEM184 B).Conclusions: Our study identified several significant SNPs and candidate genes for individual fatty acids and fatty acid groups in Chinese Wagyu cattle, and these findings will further assist the design of breeding programs for meat quality in cattle.

Impacts of Packet Collisions on Link Throughput in CSMA Wireless Networks

It is known that packet collisions in wireless networks will deteriorate system performance, hence substantial efforts have been made to avoid collision in multi-user access designs. Also, there have been many studies on throughput analysis of CSMA wireless networks. However, for a typical CSMA network in which not all nodes can sense each other, it is still not well investigated how link throughputs are affected by collisions. We note that in practical 802.11-like networks, the time is divided into mini-timeslots and packet collisions are in fact unavoidable. Thus, it is desirable to move forward to explore how collisions in such a network will affect system performance. Based on the collision-free ideal CSMA network(ICN) model, this paper attempts to analyze link throughputs when taking the backoff collisions into account and examine the effect of collisions on link throughputs. Specifically, we propose an Extended Ideal CSMA Network(EICN) model to characterize the collision effects as well as the interactions and dependency among links in the network. Based on EICN, we could directly compute link throughputs and collision probabilities. Simulations show that the EICN model is of high accuracy. Under various network topologies and protocol parameter settings, the computation error of link throughputs using EICN is kept to 4% or below. Interestingly, we find that unlike expected, the effect of collisions on link throughputs in a modest CSMA wireless network is not significant, which enriches our understanding on practical CSMA wireless networks such as Wi-Fi.

RECENT DEVELOPMENT OF ERROR CONTROL CODES FOR FUTURE COMMUNICATION AND STORAGE SYSTEMS

The outstanding performance of error control codes has attracted the interest of the information and communications theory community and industry partners for more than 20 years since Turbo codes were invented.In recent years,there are more and more scenarios in modern communication and digital storage systems,such as wireless communications,optical communications,fl ash memories,computer hard drives,sensor networks,

Na-doping-induced modification of the Cu_(2)ZnSn(S,Se)_(4)/CdS heterojunction towards efficient solar cells

It is very important to understand why a small amount of alkali metal doping in Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)solar cells can improve the conversion efficiency.In this work,Na-doped CZTSSe is prepared by a simple solution method,and then the effects on the surface properties of the absorber layer,the buffer layer growth,and the modifications of the solar cell performance induced by the Na doping are studied.The surface of the absorber layer is more Cu-depletion and less roughness due to the Na doping.In addition,the contact angle of the surface increases because of Na doping.As a consequence,the thickness of the CdS buffer layer is significantly reduced and the optical losses in the CdS buffer layer are decreased.The difference of quasi-Fermi levels(EFn-EFp) increases with a small amount of Na doping in the CZTSSe solar cell,so that open circuit voltage(VOC) increased significantly.This work offers new insights into the effects of Na doping on CZTSSe via a solution-based approach and provides a deeper understanding of the origin of the efficiency improvement of Na-doped CZTSSe thin film solar cells.

Preface to the Special Issue on Monoelemental 2D Semiconducting Materials and Their Applications

Atomically monolayer 2D material was predicted thermal dynamically unstable,until the ground-breakthrough reports of the isolation of graphene in 2004,which was shortly recognized by the Nobel Prize in 2010.Monoelemental graphene inherits the merits of simple stoichiometry and crystal structure,which offers the possibilities for basic physics scenarios demonstrations and a great deal of functional devices explorations.

Li_(2)S doping into CZTSe drives the large improvement of V_(OC) of solar cell

Alkali metal doping or sulfurization are commonly applied in Cu_(2)ZnSnSe_(4) (CZTSe) solar cell to improve the open-circuit voltage (VOC). However, alkali metal sulfide affording both alkali metal and sulfur is seldom to be studied, which restrains the development of kesterite solar cells. In this study, we evaporate Li_(2)S during selenization process and hope to provide both alkali metal and sulfur to CZTSe film. The result indicates that Li shows a gradient distribution near the surface of CZTSe film and the content of S is slight. The film quality is improved and the recombination at grain boundaries is decreased after Li_(2)S treatment. Besides, the bandgap of the absorber gets wider. Under the synergy of sulfur and lithium (mainly from lithium), the work function of the treated absorber gets higher and the conduction band offset (CBO) is in the ideal range. Combined with these contributions, the V_(OC) of the champion device treated by Li_(2)S dramatically increase by 120 mV. This study discloses that alkali metal brings the main effect on the performance of the kesterite solar cell even an alkali metal sulfide is evaporated, which deepens the understanding of sulfurization of CZTSe and also promote the progress of kesterite solar cells.

g-C_(3)N_(4) Derived Materials for Photocatalytic Hydrogen Production: A Mini Review on Design Strategies

Hydrogen production through solar energy is one of the most important pathways to meet the growing demand of renewable energy,and photocatalyst participation in solar hydrolytic hydrogen production has received great attention in recent years in terms of low cost,high efficiency,and flexible design.Particularly,g-C_(3)N_(4)(Graphitic-like carbon nitride material),as a unique material,can catalyze the hydrogen production process by completing the separation and transmission of charge.The easily adjustable pore structure/surface area,dimension,band-gap modulation and defect have shown great potential for hydrogen production from water cracking.In this review,the most recent advance of g-C_(3)N_(4) including the doping of metal and non-metal elements,and the formation of semiconductor heterojunction is highlighted.The main modification strategies and approaches for the design of g-C_(3)N_(4) for hydrogen production,as well as the influence of various materials on hydrogen evolution regarding the photocatalysis mechanism and advantages brought by theoretical calculations are specially and briefly illu-strated.Potential design pathways and strategies of g-C_(3)N_(4) are discussed.In addition,current challenges of hydrogen production from g-C_(3)N_(4) water splitting are summarized and can be expected.

A novel method for rapid and reliable detection of complex vertebral malformation and bovine leukocyte adhesion deficiency in Holstein cattle

Background： Complex vertebral malformation （CVM） and bovine leukocyte adhesion deficiency （BLAD） are two autosomal recessive lethal genetic defects frequently occurring in Holstein cattle, identifiable by single nucleotide polymorphisms. The objective of this study is to develop a rapid and reliable genotyping assay to screen the active Holstein sires and determine the carrier frequency of CVM and BLAD in Chinese dairy cattle population. Results： We developed real-time PCR-based assays for discrimination of wild-type and defective alleles, so that carriers can be detected. Only one step was required after the DNA extraction from the sample and time consumption was about 2 hours. A total of 587 Chinese Holstein bulls were assayed, and fifty-six CVM-carriers and eight BLAD-carriers were identified, corresponding to heterozygote carrier frequencies of 9.54% and 1.36%, respectively. The pedigree analysis showed that most of the carriers could be traced back to the common ancestry, Osborndale Ivanhoe for BLAD and Pennstate Ivanhoe Star for CVM. Conclusions： These results demonstrate that real-time PCR is a simple, rapid and reliable assay for BLAD and CVM defective allele detection. The high frequency of the CVM allele suggests that implementing a routine testing system is necessary to gradually eradicate the deleterious gene from the Chinese Holstein population.

Two-step growth of VSe_2 films and their photoelectric properties

We put forward a two-step route to synthesize vanadium diselenide(VSe_2), a typical transition metal dichalcogenide(TMD). To obtain the VSe_2 film, we first prepare a vanadium film by electron beam evaporation and we then perform selenization in a vacuum chamber. This method has the advantages of low temperature, is less time-consuming, has a large area, and has a stable performance. At 400?C selenization temperature, we successfully prepare VSe_2 films on both glass and Mo substrates. The prepared VSe_2 has the characteristic of preferential growth along the c-axis, with low transmittance.It is found that the contact between Al and VSe_2/Mo is ohmic contact. Compared to Mo substrate, lower square resistance and higher carrier concentration of the VSe_2/Mo sample reveal that the VSe_2 film may be a potential material for thin film solar cells or other semiconductor devices. The new synthetic strategy that is developed here paves a sustainable way to the application of VSe_2 in photovoltaic devices.

Electronic band structures and optical properties of atomically thin AuSe: first-principle calculations

As a large family of 2D materials, transition metal dichalcogenides(TMDs) have stimulated numerous works owing to their attractive properties. The replacement of constituent elements could promote the discovery and fabrication of new nanofilm in this family. Using precious metals, such as platinum and palladium, to serve as transition metals combined with chalcogen is a new approach to explore novel TMDs. Also, the proportion between transition metal and chalcogen atoms is found not only to exist in conventional form of 1 : 2. Herein, we reported a comprehensive study of a new 2D precious metal selenide, namely AuSe monolayer. Based on density functional theory, our result indicated that AuSe monolayer is a semiconductor with indirect band-gap of 2.0 eV, which possesses superior dynamic stability and thermodynamic stability with cohesive energy up to–7.87 eV/atom. Moreover, it has been confirmed that ionic bonding predominates in Au–Se bonds and absorption peaks in all directions distribute in the deep ultraviolet region. In addition, both vibration modes dominating marked Raman peaks are parallel to the 2D plane.

First-principle study of puckered arsenene MOSFET

Two-dimensional material has been regarded as a competitive silicon-alternative with a gate length approaching sub-10 nm,due to its unique atomic thickness and outstanding electronic properties.Herein,we provide a comprehensively study on the electronic and ballistic transport properties of the puckered arsenene by the density functional theory coupled with nonequilibrium Green’s function formalism.The puckered arsenene exhibits an anisotropic characteristic,as effective mass for the electron/hole in the armchair and zigzag directions is 0.35/0.16 m0 and 1.26/0.32 m0.And it also holds a high electron mobility,as the highest value can reach 20045 cm2V–1s–1.Moreover,the puckered arsenene FETs with a 10-nm channel length possess high on/off ratio above 105 and a steep subthreshold swing below 75 mV/dec,which have the potential to design high-performance electronic devices.Interestingly,the channel length limit for arsenene FETs can reach 7-nm.Furthermore,the benchmarking of the intrinsic arsenene FETs and the 32-bit arithmetic logic unit circuits also shows that the devices possess high switching speed and low energy dissipation,which can be comparable to the CMOS technologies and other CMOS alternatives.Therefore,the puckered arsenene is an attractive channel material in next-generation electronics.

An MDP Based Energy Efficient Transmission Policy for Wireless Terminals

In wireless network, terminals are usually energy constrained. In order to extend the lifetime of the terminal, the limited energy must be utilized in an efficient manner. In this paper, under the constant transmission power scenario, we propose an Energy Efficient Transmission Policy (EETP) which is derived by using Markov Decision Process (MDP). The simulation results show that compared with the Threshold Transmission Policy (TTP), the proposed policy can reduce the energy consumption significantly, while satisfying the performance demand at the same time.

First-principles Simulations of Tunneling FETs Based on van der Waals MoTe2/SnS2 Heterojunctions with Gate-to-drain Overlap Design

The electronic properties and transport properties of MoTe2/SnS2 heterostructure Tunneling FETs are investigated by the density functional theory coupled with non-equilibrium Green’s function method.Two dimensional(2D)monolayer MoTe2 and SnS2 are combined to a vertical van der Waals heterojunction.A small staggered band gap is formed in the overlap region,while larger gaps remain in the underlap source and drain regions of monolayer MoTe2 and SnS2 respectively.Such a type-II heterojunction is favorable for tunneling FET.Furthermore,we suggest short stack length and large gate-to-drain overlap to enhance the on-state current suppress the leakage current respectively.The numerical results show that at a low drain to source voltage Vds=0.05V,On/Off current ratio can reach 108 and the On-state currents is over 20μA/μm for ntype devices.Our results present that van der Waals heterostructure TFETs can be potential candidate as next generation ultra-steep subthreshold and low-power electronic applications.

揭示银关联缺陷的双重作用:环保型AgIn0.5Ga0.5S2中发光和载流子动力学的操纵者

AgIn_(0.5)Ga_(0.5)S_(2)由于环境友好、合成成本低、成分灵活可调等优点在许多领域受到广泛关注.适当的直接带隙、无禁戒跃迁和高激子结合能使其成为一种有前途的发光材料.多组分体系的演化丰富了光电特性,并使其本征缺陷更加复杂.反过来,这些缺陷对光电性能有重要影响,从而影响其发光性能.然而,对于这类半导体,在实验中观察到的与发光相对应的点缺陷的微观机制大多是未知的或间接推断的.本工作系统地揭示了AgIn_(0.5)Ga_(0.5)S_(2)的微观缺陷与发光之间的机制.热力学稳定性表明AgIn_(0.5)Ga_(0.5)S_(2)是亚稳态的并且与次生相之间存在显著的竞争.此外,计算的缺陷结果表明,与银关联的缺陷是幕后操纵者.两个浅能级缺陷(VAg和Agi)充当载流子提供者,而四个深能级反位缺陷(AgIn,AgGa,InAg和GaAg)充当载流子湮灭者.最后,载流子动力学的研究揭示了四种深能级反位缺陷对载流子辐射过程的不利影响.这些旨在为AgIn_(0.5)Ga_(0.5)S_(2)在发光领域的功能应用提供重要指导.

通过高通量研究识别用于本征陡坡晶体管的原子级薄孤立能带沟道材料

Developing low-power FETs holds significant importance in advancing logic circuits,especially as the feature size of MOSFETs approaches sub-10 nanometers.However,this has been restricted by the thermionic limitation of SS,which is limited to 60 mV per decade at room temperature.Herein,we proposed a strategy that utilizes 2D semiconductors with an isolated-band feature as channels to realize subthermionic SS in MOSFETs.Through high-throughput calculations,we established a guiding principle that combines the atomic structure and orbital interaction to identify their sub-thermionic transport potential.This guides us to screen 192 candidates from the 2D material database comprising 1608 systems.Additionally,the physical relationship between the sub-thermionic transport performances and electronic structures is further revealed,which enables us to predict 15 systems with promising device performances for low-power applications with supply voltage below 0.5 V.This work opens a new way for the low-power electronics based on 2D materials and would inspire extensive interests in the experimental exploration of intrinsic steep-slope MOSFETs.

Electron donor–acceptor (D-A) tuning to achieve soluble covalent organic polymers for optoelectronic devices

Covalent organic polymers(COPs)have emerged as a unique class of luminescent polymers with pre-designed quasi-ordered architectures.However,their layered stacks and limited solubility preclude further processing for large-scale applications in devices,especially optoelectronic equipment.Herein,a universal strategy to adjust the electron donor–acceptor(D-A)moieties of the building blocks in COPs is proposed,achieved by in situ charge exfoliation of COP blocks into few-layer true solutions in(Lewis)acid and base media.The electron D-A moieties of the building blocks endow the COPs with the ability to accept or donate electrons,by altering the electron cloud distribution as well as the relative energy levels of the frontier molecular orbitals.The resultant soluble COPs can easily be processed into a uniform film by solution processing via the spin-coat method.The obtained COP-N achieves efficient and stable perovskite electroluminescence as a novel hole injection material on indium tin oxide,and the operating lifetime for a perovskite quantum dot light-emitting diodes device exceeds that of a poly(ethylene dioxythiophene):polystyrene sulphonate counterpart.This straightforward electronic regulation strategy provides a new avenue for the rational synthesis of processable reticular molecular polymers for practical electronic devices.

Fast and direct identification of SARS-CoV-2 variants via 2D InSe field-effect transistors

As the COVID-19 pandemic evolves and new variants emerge,the development of more efficient identification approaches of variants is urgent to prevent continuous outbreaks of SARS-CoV-2.Field-effect transistors(FETs)with two-dimensional(2D)materials are viable platforms for the detection of virus nucleic acids(NAs)but cannot yet provide accurate information on NA variations.Herein,2D Indium selenide(InSe)FETs were used to identify SARSCoV-2 variants.The device's mobility and stability were ensured by atomic layer deposition(ALD)of Al_(2)O_(3).The resulting FETs exhibited sub-fM detection limits ranging from 10^(–14)M to 10^(–8)M.The recognition of single-nucleotide variations was achieved within 15 min to enable the fast and direct identification of two core mutations(L452R,R203M)in Delta genomes(p<0.01).Such capability originated from the trap states in oxidized InSe(InSe_(1-x)O_(x))after ALD,resulting in traps-involved carrier transport responsive to the negative charges of NAs.In sum,the proposed approach might highly provide epidemiological information for timely surveillance of the COVID pandemic.