Non-destructive buffer enabling near-infrared-transparent inverted inorganic perovskite solar cells toward 1400 h light-soaking stable perovskite/Cu(In,Ga)Se_(2) tandem solar cells

Near-infrared(NIR)transparent inverted all-inorganic perovskite solar cells(PSCs)are excellent top cell candidates in tandem applications.An essential challenge is the replacement of metal contacts with transparent conductive oxide(TCO)electrodes,which requires the introduction of a buffer layer to prevent sputtering damage.In this study,we show that the conventional buffers(i.e.,small organic molecules and atomic layer deposited metal oxides)used for organic-inorganic hybrid perovskites are not applicable to all-inorganic perovskites,due to non-uniform coverage of the vulnerable layers underneath,deterioration upon ion bombardment and moisture induced perovskite phase transition,A thin film of metal oxide nanoparticles by the spin-coating method serves as a non-destructive buffer layer for inorganic PSCs.All-inorganic inverted near-infrared-transparent PSCs deliver a PCE of 17.46%and an average transmittance of 73.7%between 780 and 1200 nm.In combination with an 18.56%Cu(In,Ga)Se_(2) bottom cell,we further demonstrate the first all-inorganic perovskite/CIGS 4-T tandem solar cell with a PCE of 24.75%,which exhibits excellent illumination stability by maintaining 86.7%of its initial efficiency after 1400 h.The non-destructive buffer lays the foundation for efficient and stable NIR-transparent inverted inorganic perovskite solar cells and perovskite-based tandems.

Charge-transfer-regulated bimetal ferrocene-based organic frameworks for promoting electrocatalytic oxygen evolution

The ferrocene(Fc)-based metal-organic frameworks(MOFs)are regarded as compelling platforms for the construction of efficient and robust oxygen evolution reaction(OER)electrocatalysts due to their superior conductivity and flexible electronic structure.Herein,density functional theory simulations were addressed to predict the electronic structure regulations of CoFc-MOF by nickel doping,which demonstrated that the well-proposed CoNiFc-MOFs delivered a small energy barrier,promoted conductivity,and well-regulated d-band center.Inspired by these,a series of sea-urchin-like CoNiFc-MOFs were successfully synthesized via a facile solvothermal method.Moreover,the synchrotron X-ray and X-ray photoelectron spectroscopy measurements manifested that the introduction of nickel could tailor the electronic structure of the catalyst and induce the directional transfer of electrons,thus optimizing the rate-determining step of^(*)O→^(*)OOH during the OER process and yielding decent overpotentials of 209 and 252 mV at 10 and 200 mA cm^(−2),respectively,with a small Tafel slope of 39 mV dec^(−1).This work presents a new paradigm for developing highly efficient and durable MOF-based electrocatalysts for OER.

Cooperative Caching for Scalable Video Coding Using Value-Decomposed Dimensional Networks

Scalable video coding(SVC)has been widely used in video-on-demand(VOD)service,to efficiently satisfy users’different video quality requirements and dynamically adjust video stream to timevariant wireless channels.Under the 5G network structure,we consider a cooperative caching scheme inside each cluster with SVC to economically utilize the limited caching storage.A novel multi-agent deep reinforcement learning(MADRL)framework is proposed to jointly optimize the video access delay and users’satisfaction,where an aggregation node is introduced helping individual agents to achieve global observations and overall system rewards.Moreover,to cope with the large action space caused by the large number of videos and users,a dimension decomposition method is embedded into the neural network in each agent,which greatly reduce the computational complexity and memory cost of the reinforcement learning.Experimental results show that:1)the proposed value-decomposed dimensional network(VDDN)algorithm achieves an obvious performance gain versus the traditional MADRL;2)the proposed VDDN algorithm can handle an extremely large action space and quickly converge with a low computational complexity.

Facile Synthesis of Mo2C Nanocrystals Embedded in Nanopo- rous Carbon Network for Efficient Hydrogen Evolution

Exploring facile and easily-scalable methods for synthesizing earth-abundant, cost-effective and efficient hy- drogen evolution reaction （HER） electrocatalysts is essential for the mass production of hydrogen as a clean and sustainable energy carrier. We report here a simple strategy to produce Mo2C nanocrystals embedded in carbon network （Mo2C@C） by the direct pyrolysis of ammonium molybdate and polyvinylpyrrolidone （PVP）. It is found that PVP can be effectively used as a single source to form carbides and carbon network. The long polymer chain and coordinating capability with transition metal of PVP make it possible to form connected porous carbon network and well-dispersed MozC nanocrystals in several nanometers. The carbonization of PVP not only effectively in-situ prevents the aggregation of Mo2C nanocrystals during their formation, but also provides conductive porous matrix. As a result, the Mo2C@C composite exhibits the superior electrocatalytic performance for HER, which can be as- cribed to the large number of active sites from plenty of small MORC nanocrystals and the efficient mass and elec- tron transport network from carbon matrix. This strategy may inspire the exploration of cost-effective functional polymer as single source for both carbon precursor and nanostructure-directed reagent to mass-produce well-defined metal carbides nanostructures embedded in porous carbon network for energy applications.

Luminescent metal-organic frameworks for nitro explosives detection

Metal-organic frameworks （MOFs） have been emerging as important multifunctional hybrid materials, not only due to the diversify framework architectures, but also contribute to the rich interactions among metals, ligands and guests. Nitro explosives have important influences tbr environmental protection and national homeland security, in this review, a brief description of luminescent MOFs is presented, accompanied by a short comment on the four types of metal-based luminescent MOFs as sensing materials for nitro explosives detection. Then the trends and challenges of luminescent MOFs as sensing materials ibr nitro explosives are also prospected.

Rational confinement engineering of MOF-derived carbonbased electrocatalysts toward CO_(2)reduction and O_(2)reduction reactions

The goal of global carbon peak and neutrality gives an impetus to the utilization of clean energy(e.g.,fuel cell)and carbon dioxide(CO_(2))at a large scale,where the oxygen reduction reaction(ORR)and CO_(2)reduction reaction(CO_(2)RR)are the key reactions via the sustainable system,respectively.As a main precursor for fabricating affordable carbon-based electrocatalysts with uniformly dispersed active centers and tailorable performances for ORR and CO_(2)RR,metal organic frameworks(MOFs)have captured a surge of interest in recent years.Despite the facilitated development of MOF-derived carbon-based electrocatalysts by many investigations,it is still plagued by high overpotential and unsatisfied life span,which are greatly determined by the efficient and alterable confinement effect on synthesis and performance.In this review,firstly,the confined synthetic strategies(doping engineering,defect engineering,geometric engineering,etc.)of MOF-derived carbon-based electrocatalysts with multi-sized active centers(atom,atomic clusters and nanoparticles(NPs))are systematically summarized;secondly,the confinement effect on the interaction of ORR and CO_(2)RR intermediates,as well as the catalytic durability and activity,was discussed from chemical and physical aspects.In the end,the review discusses the remaining challenges and emerging research topics in the future,including support upgradation and catalyst innovation,high selectivity and effective confinement synthesis,in situ and operando characterization techniques,theoretical investigation,and artificial intelligence(AI)assistant.The new understanding and insights into these aspects will guide the rational confinement concept of MOF-derived carbon-based electrocatalysts for ORR and CO_(2)RR with optimized performances in terms of confinement engineering and are believed to be helpful for filling the existing gaps between scientific communities and practical use.

In situ transformation of Cu2O@MnO2 to Cu@Mn（OH）2 nanosheet-on-nanowire arrays for efficient hydrogen evolution

The development of new non-precious metal catalysts and understanding the origin of their activity for the hydrogen evolution reaction （HER） are essential for rationally designing highly active low-cost catalysts as alternatives to state-of-the-art precious metal catalysts. Herein, manganese oxide/hydroxide was demonstrated as a highly active electrocatalysts for the HER by fabricating MnO2 nanosheets coated with Cu2O nanowire arrays （Cu2O@MnO2 NW@NS） on Cu foam followed by an in situ chronopotentiometry （CP） treatment. It was discovered that the in situ transformation of Cu2O@MnO2 into Cu@Mn（OH）2 NW@NS by the CP treatment drastically boosted the catalytic activity for the HER due to an enhancement of its intrinsic activity. Together with the benefits from such （3D） core-sheU arrays for exposing more accessible active sites and efficient mass and electron transfers, the resulting Cu@Mn（OH）2 NW@NS exhibited excellent HER activity and outstanding durability in terms of a low overpotential of 132 mV vs. RHE at 10 mA/cm2, Overall, we expect these findings to generate new opportunities for the exploration of other Mn-based nanomaterials as efficient electrocatalysts and enable further understanding of their catalytic processes.

Pyrolysis transformation of ZIF-8 wrapped with polytriazine to nitrogen enriched core-shell polyhedrons carbon for supercapacitor

This work presents a simple effective strategy to synthesize N-doped and shell-controlled carbon nanocages through a package baking approach.A green approach to synthesize core-shell ZIF-8@PTZ nanoparticles involves zinc contained ZIF-8 core wrapped by a N-enriched polytriazine(PTZ).Synthesized core-shell ZIF-8@PTZ nanoparticles are calcinated to further sublime zinc through PTZ shell and washed by HC1,leaving a porous carbon structure.At the meantime,hollow cavities were introduced into N-doped carbon polyhedrons via the sacrifice of ZIF-8 template(noted as ZIF-8@C/N-x).The electrochemical performance of the ZIF-8@C/N-x as supercapacitor electrode has demonstrated high energy density and specific capacitance,as well as a long-term cycleability showing 92%capacitance retention after 10000 cycles.There is a systematic correlation between micro-/meso-porosity of ZIF-8@C/N-x and their electrochemical performances.

Highly π-extended copolymer as additive-free hole- transport material for perovskite solar cells

Organolead halide perovskite solar ceils have achieved a certified power- conversion efficiency （PCE） of 22.1% and are thus among the most promising candidates for next-generation photovoltaic devices. To date, most high-efficiency perovskite solar cells have employed arylamine-based hole-transport materials （HTMs）, which are expensive and have a low mobility. The complicated doping procedures and the potentially stability-adverse dopants used in these HTMs are among the major bottlenecks for the commercialization of perovskite solar cells （PSCs）. Herein, we present a polythiophene-based copolymer （PDVT-10） with a hole mobility up to 8.2 cm2-V-l.s-1 and a highest occupied molecular orbital level of -5.28 eV as a hole-transport layer （HTL） for a PSC. A device based on this new HTM exhibited a high PCE of 13.4% under 100 mW-cm-2 illumination, which is one of the highest PCEs reported for the dopant-free polymer-based HTLs. Moreover, PDVT-10 exhibited good solution processability, decent air stability, and thermal stability, making it a promising candidate as an HTM for PSCs.

Carrier management makes perovskite solar cells approaching Shockley-Queisser limit

Metal halide perovskite solar cells(PSCs)have drawn enormous attention due to their great potential to share the market of silicon solar cells[1–3].During the past few years,significant progress has been made in fabrication method,chemical composition,defect passivation,and strain regulation of perovskite materials,making PSCs one of the most promising solution-processed photovoltaic technologies with high efficiency and low cost[4–6].

Physical layer security techniques for data transmission for future wireless networks

The broadcast nature of wireless communication systems makes wireless trans-mission extremely susceptible to eavesdropping and even malicious interference.Physical layer security technology can e ectively protect the private information sent by the trans-mitter from being listened to by illegal eavesdroppers,thus ensuring the privacy and security of communication between the transmitter and legitimate users.Thus,the main design goal of physical layer security is to increase the performance di erence between the link of the legitimate receiver and that of the eavesdropper using well-designed transmission schemes.The development of mobile communication presents new challenges to physical layer security research.This paper provides a survey of the physical layer security research on various promising mobile technologies from secure key generation and keyless techniques,including secure key generation,directional modulation(DM),spatial modulation(SM),covert communication,and intelligent re ecting surface(IRS)-aided communication.Finally,the future topics and the unresolved technical challenges are presented in physical layer security for mobile communications.

Fibrillarin redistributes to the spindle poles and partially colocalizes with NuMA during mitosis

Fibrillann, a major protein in the nucleolus. is known to redistribute during mitosis from the nucleolus to the cytosol, and is related to the dynamics of post-mitotic reassembly of the nucleolus. To better understand the dynamic behavior and the relationship with other cytoplasmic structures, we have now expressed fibrillarin-pDsRedl fusion protein in HeLa cells. The results showed that a part of fibrillarin was associated with mitotic spindle poles in the mitotic cells. Nocodazole-induced microtubule depolymeri-zation resulted in fibrillarin redistribution throughout the cytoplasm, and removal of nocodazole resulted in relocaliza-tion of fibrillarin at the polar region during the mitotic spindles reassembly. In a mitotic cell free system, fibrillarin was found in the center of taxol-induced microtubule asters. Moreover, fibrillarin was found to colocalize with the nuclear mitotic apparatus protein (NuMA) at the poles of mitotic cells. Therefore, it is postulated that the polar redistribution of

Optoeletronic investigation of Cu2ZnSn(S,Se)4 thin-films ＆ Cu2Zn Sn(S,Se)4/CdS interface with scanning probe microscopy

The kesterite-structured semiconductor Cu_2 Zn Sn(S,Se)_4(CZTSSe) is prepared by spin coating a non-hydrazine precursor and annealing at Se atmosphere. Local electrical and optoelectronic properties of the CZTSSe thin-film are explored by Kelvin probe force microscopy and conductive atomic force microscopy. Before and after irradiation, no marked potential bending and very low current flow are observed at GBs, suggesting that GBs behave as a charge recombination site and an obstacle for charge transport. Furthermore, Cd S nano-islands are synthesized via successive ionic layer adsorption and reaction(SILAR) method on the surface of CZTSSe. By comparing the work function and current flow change of CZTSSe and Cd S in dark and under illumination, we demonstrate photo-induced electrons and holes are separated at the interface of p-n junction and transferred in Cd S and CZTSSe, respectively.

中继与智能超表面网络中的隐蔽通信

Covert communication aims to prevent the warden from detecting the presence of communications,i.e.with a negligible detection probability.When the distance between the transmitter and the legitimate receiver is large,large transmission power is needed,which in turn increases the detection probability.Relay is an effective technique to tackle this problem,and various relaying strategies have been proposed for long-distance covert communication in these years.In this article,we first offer a tutorial on the relaying strategies utilized in covert transmission.With the emergence of reflecting intelligent surface and its application in covert communications,we propose a hybrid relay-reflecting intelligent surface(HR-RIS)-assisted strategy to further enhance the performance of covert communications,which simultaneously improves the signal strength received at the legitimate receiver and degrades that at the warden relying on optimizing both the phase and the amplitude of the HR-RIS elements.The numerical results show that the proposed HR-RIS-assisted strategy significantly outperforms the conventional RIS-aided strategy in terms of covert rate.