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Any tissue or cell in the body can be attacked by electromagnetic (EM) radiation, especially causing serious damage to human orthopedics. The ideal metacomposites with low-dispersion weakly negative permittivity and freely tuned response characteristics are promising for high-performance EM shielding which effectively protects human orthopedics. Herein, unveiling the precisely regulation mechanism of ε'-negative response and subsequently clarifying the perfect EM shielding effect of metacomposites is crucial for the development of this field. In this work, we offered the systematical research on the ε'-negative properties at 100 MHz-1 GHz region, along with the percolation effect, dielectric loss and impedance character, demo for monolayer graphene/CaCu3Ti4O12(MLGR/CCTO) nanocomposites. Further, we firstly brought up an effective evaluation method for frequency dispersion of ε'-negative response, especially directed against the Drude-type frequency spectrum, which reflected the strength and stability of plasmonic oscillations within the 3-dimensional (3D) carbon networks. By performing the density functional theory (DFT) calculations of the interfaces between MLGR and CCTO, we successfully demonstrated the regulation of dielectric response mechanism which includes the abundant electric dipoles assembled at MLGR/CCTO interfaces and the plasmonic state consisting of multitude free electrons in MLGR sheets. These results exactly correspond to the obtained boosting EM shielding performance of ε'-negative metacomposites, which will stimulate the development of conventional EM devices by integrating exotic EM effects, to fuse metacomposites and universal functional composites.

The topic recognition for dynamic topic number can realize the dynamic update of super parameters, and obtain the probability distribution of dynamic topics in time dimension, which helps to clear the understanding and tracking of convection text data. However, the current topic recognition model tends to be based on a fixed number of topics Kand lacks multi-granularity analysis of subject knowledge. Therefore, it is impossible to deeply perceive the dynamic change of the topic in the time series. By introducing a novel approach on the basis of Infinite Latent Dirichlet allocation model, a topic feature lattice under the dynamic topic number is constructed. In the model, documents, topics and vocabularies are jointly modeled to generate two probability distribution matrices: Documents-topics and topic-feature words. Afterwards, the association intensity is computed between the topic and its feature vocabulary to establish the topic formal context matrix. Finally, the topic feature is induced according to the formal concept analysis (FCA) theory. The topic feature lattice under dynamic topic number (TFL_DTN) model is validated on the real dataset by comparing with the mainstream methods. Experiments show that this model is more in line with actual needs, and achieves better results in semi-automatic modeling of topic visualization analysis.

The perovskite-based optoelectronic applications always suffer from stability issues, due to the intrinsic chemical instability of the perovskite materials. Besides, poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is always utilized as an anode buffer layer in thin-film perovskite light-emitting diodes (PeLEDs), which may lead to stability issues due to the hygroscopic and acidic nature of PEDOT:PSS. In this paper, inorganic metal oxide NiOxis employed as a hole injection layer (HIL) and hole transport layer (HTL) to substitute detrimental PEDOT:PSS in all-inorganic PeLEDs. Then fully covered CsPbBr3polycrystalline films are fabricated by using a one-step spin-coating method based on nonstoichiometric and polymer-assisted perovskite precursor solutions. The optimized films not only have compact morphology but also have excellent photoluminescence quantum yield (PLQY). Encouragingly, by introducing a metal oxide NiOx, the CsPbBr3PeLEDs show a maximum luminance of 23 828 cd m–2and maximum current efficiency (CE) of 9.54 cd A–1, which lead to a 1.6-fold and 3.3-fold increase compared to the PeLEDs with a PEDOT:PSS HIL. Besides, the inorganic PeLEDs show high color purity with a full-width at half-maximum (fwhm) of only 16 nm. The combination of inorganic NiOxwith inorganic perovskite also shows improved operation stability of devices, which paves the way for highly efficient all-inorganic PeLEDs.

A better charge balance is realized for blue quantum dot light‐emitting diodes (QLEDs) through doping the charge transport layer (CTL) to improve hole injection and suppress redundant electrons. High performance blue QLEDs were achieved by fine‐tuning the charge balance within the emitting layer.

The effects of cementitious materials used in the early conservation of stony cultural heritage on sandstones have yet to be clarified. The impact of cementitious materials on mechanical and physicochemical properties was investigated by designing sandstones for wet and dry cycling in neutral and alkaline solutions (pure water, sodium hydroxide, calcium hydroxide, ordinary cement, and low alkaline cement). The sandstone was examined before and after the wet and dry cycles using X-ray fluorescence spectrometry (XRF), ion chromatography (IC), and X-ray diffractometry (XRD) to characterize the deterioration of the sandstone material caused by cement from macro and micro perspectives and the diffusion characteristics of the soluble components of cement in the sandstone. The results show that the concentration of Ca2+precipitated within the sandstone after cycling is higher than that of Cl-, SO42-, NO3-, Na+, and K+and has the most significant influence on the sandstone properties. In terms of mass, there is a 3%−6% mass loss in the sandstone after dry and wet cycling in NaOH solution and a 2%−7% mass accumulation in cement and Ca(OH)2solution. The cumulative damage (DN) variation pattern of sandstones was also analyzed based on wave velocity variation. The damage rate fluctuated in a wider region of 6%−30% for medium-weathered sandstones subjected to dry and wet cycling in cement solution compared to fresh sandstones, and 9%−20% for fresh sandstones. In addition, it was found that the deterioration process of sandstone by cement materials is physicochemically synergistic, while the macro-mechanical properties correspond closely to the changes in material composition.

For bulk heterojunction polymer solar cells (PSCs), the donors and acceptors featuring specific phase separation and concentration distribution within the electron donor/acceptor blends crucially affect the exciton dissociation and charge transportation. Herein, efficient and stable nonfullerene inverted PSCs incorporating a phase separated photoactive layer and a titanium chelate electrode modification layer are demonstrated. Water contact angle (WCA), scanning kelvin probe microscopy (SKPM), and atomic force microscopy (AFM) techniques are implemented to characterize the morphology of photoactive layers. Compared with the control conventional device, the short-circuit current density (Jsc) is enhanced from 14.74 to 17.45 mAcm–2. The power conversion efficiency (PCE) for the inverted PSCs with a titanium (diisopropoxide)-bis-(2,4-pentanedionate) (TIPD) layer increases from 9.67% to 11.69% benefiting from the declined exciton recombination and fairly enhanced charge transportation. Furthermore, the nonencapsulated inverted device with a TIPD layer demonstrates the best long-term stability, 85% of initial PCE remaining and an almost undecayed open-circuit voltage (Voc) after 1440 h. Our results reveal that the titanium chelate is an excellent electrode modification layer to incorporate with a vertical phase separated photoactive layer for producing high-efficiency and high-stability inverted nonfullerene PSCs.

For planar structured organic–inorganic hybrid perovskite solar cells (PerSCs) with the poly(3,4-ethylenedioxythiophene:polystyrene sulfonate) (PEDOT:PSS) hole transport layer, the open-circuit voltage (Voc) of the device is limited to be about 1.0 V, resulting in inferior performance in comparison with TiO2-based planar counterparts. Therefore, increasing Vocof the PEDOT:PSS-based planar device is an important way to enhance the efficiency of the PerSCs. Herein, we demonstrate a novel approach for perovskite film formation and the film is formed by slow growth from lead acetate precursor via a one-step spin-coating process without the thermal annealing (TA) process. Because the perovskite layer grows slowly and naturally, high-quality perovskite film can be achieved with larger crystalline particles, less defects, and smoother surface morphology. Ultraviolet absorption, X-ray diffraction, scanning electron microscopy, steady-state fluorescence spectroscopy (photoluminescence), and time-resolved fluorescence spectroscopy are used to clarify the crystallinity, morphology, and internal defects of perovskite thin films. The power conversion efficiency of p–i–n PerSCs based on slow-grown film (16.33%) shows greatly enhanced performance compared to that of the control device based on traditional thermally annealed perovskite film (14.33%). Furthermore, the Vocof the slow-growing device reaches 1.12 V, which is 0.1 V higher than that of the TA device. These findings indicate that slow growth of the perovskite layer from lead acetate precursor is a promising approach to achieve high-quality perovskite film for high-performance PerSCs.

For organic-inorganic hybrid perovskite solar cells (PerSCs), the crystallinity and the grain size of the perovskite films are crucial for effective exciton dissociation and charge transportation. Herein, we introduce methylammonium halide (MABr and MACl) intermediates to control the perovskite formation processes via intramolecular exchange. X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray Photoelectron Spectroscopy (XPS) are used to monitor the transition from intermediate to perovskite. It is particularly noteworthy that as Cl-and MA+are removed from the film as MACl vapor, the intermediate derived from Cl-Hybrid eventually turns into FAPbI3perovskite after thermal annealing. The morphology, crystallinity, fluorescence lifetime and the stability of perovskite films derived from different methylammonium halide intermediates are also investigated, and PerSCs based on different perovskite films are fabricated. The PerSCs derived from MACl intermediate exhibit the best photovoltaic performance with a PCE of 19.16%, and the PCE reaches 15.87% for MABr intermediated PerSCs, much higher than that (13.72%) of the control device without methylammonium halide intermediates. Furthermore, MACl intermediated PerSCs demonstrate the best stability due to the highest crystallinity. Our findings indicate that methylammonium halide intermediating is a feasible and effective approach to acquire high crystallinity of perovskite film for high performance and stable PerSCs.

For organic–inorganic perovskite solar cells (PerSCs), the electron transport layer (ETL) plays a crucial role in efficient electron extraction and transport for high performance PerSCs. Fullerene and its derivatives are commonly used as ETL for p–i–n structured PerSCs. However, these spherical small molecules are easy to aggregate with high annealing temperature and thus induce morphology stability problems. N-type conjugated polymers are promising candidates to overcome these problems due to the tunable energy levels, controllable aggregation behaviors, and good film formation abilities. Herein, a series of perylene diimide (PDI) based polymers (PX-PDIs), which contain different copolymeried units (X), including vinylene (V), thiophene (T), selenophene (Se), dibenzosilole (DBS), and cyclopentadithiophene (CPDT), are introduced as ETL for p–i–n structured PerSCs. The effect of energy alignment, electron mobility, and film morphology of these ETLs on the photovoltaic performance of the PerSCs are fully investigated. Among the PX-PDIs, PV-PDI demonstrates the deeper LUMO energy level, the highly delocalized LUMO electron density, and a better planar structure, making it the best electron transport material for PerSCs. The planar heterojunction PerSC with PV-PDI as ETL achieves a power conversion efficiency (PCE) of 10.14%, among the best values for non-fullerene based PerSCs.

For polymer solar cells (PSCs), the interfaces between the back and front contacts with the photoactive layer play a crucial role for charge extraction. Herein, we demonstrate high performance PSCs with dual functional tantalum methoxide (Ta-OMe) cathode interfacial layer, which can reduce the interface energy barrier and form a light trapping structure with reflective metal electrode. The energy level of Ta-OMe is investigated by ultraviolet photoelectron spectroscopy (UPS). The composition of the Ta-OMe film is confirmed by X-ray photoelectron spectroscopy (XPS). The surface morphologies of the photoactive layer with and without Ta-OMe layer are measured by scanning electron microscopy (SEM) and tapping mode atomic force microscopy (AFM). Three polymer donors with different band gaps and two classical fullerene acceptors were selected as photoactive materials for fabrication PSCs. The PSCs with Ta-OMe interfacial layer exhibit superior performance in comparison with devices which Al and Ca/Al based devices. The great enhancement in Jscis associated with additional absorption (ΔαAbs) and the additional EQE (ΔαEQE). The four parameters of Voc, Jsc, FF, and PCE for device with Ta-OMe reach 0.80V, 18.55mA/cm2, 70%, and 10.18%, respectively, among the best values reported for PTB7-Th:PC70BM based PSCs.

The insertion of an appropriate interfacial buffer layer between the photoactive layer and the contact electrodes makes a great impact on the performance of polymer solar cells (PSCs). Ideal interfacial buffer layers could minimize the interfacial traps and the interfacial barriers caused by the incompatibility between the photoactive layer and the electrodes. In this work, we utilized solution-processed hafnium(IV) acetylacetonate (Hf(acac)4) as an effective cathode buffer layer (CBL) in PSCs to optimize the energy level alignment between the photoactive layer and the cathode contact, with the short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) all simultaneously improved with Hf(acac)4CBL, leading to enhanced power conversion efficiencies (PCEs). Ultraviolet photoemission spectroscopy (UPS) and scanning Kelvin probe microscopy (SKPM) were performed to confirm that the interfacial dipoles were formed with the same orientation direction as the built-in potential between the photoactive layer and Hf(acac)4CBL, benefiting the exciton separation and electron transport/extraction. In addition, the optical characteristics and surface morphology of the Hf(acac)4CBL were also investigated.

In this paper, the blockage effects on a rectangular antenna are investigated through numerical simulation, and a correction method for the wind load coefficients is presented. In terms of the separation pressure measured by the wind tunnel test and the law of separation pressure with blockages achieved from the numerical simulation, we derive a relationship for base pressure coefficient of the rectangular antenna with various blockages. Adopting the formula based on the potential flow theory, the drag coefficient without blockage can be obtained. Using the base pressure coefficient to re-normalise the pressure coefficient, the characteristic that the re-normalised pressure coefficient the antenna is independent of the blockage ratio is verified. Furthermore, the pressure distributions on the rectangular antenna without blockage are obtained by the re-normalised pressure coefficient. The corrected results show that the blockage effect on pressure and drag force on the rectangular antenna both are removed effectively.

Efficient polymer solar cells (PSCs) with enhanced open-circuit voltage (Voc) are fabricated by introducing solution-processed and UV-ozone (UVO)-treated nickel acetate (O-NiAc) as an anode buffer layer. According to X-ray photoelectron spectroscopy data, NiAc partially decomposed to NiOOH during the UVO treatment. NiOOH is a dipole species, which leads to an increase in the work function (as confirmed by ultraviolet photoemission spectroscopy), thus benefitting the formation of ohmic contact between the anode and photoactive layer and leading to increased Voc. In addition, the UVO treatment improves the wettability between the substrate and solvent of the active layer, which facilitates the formation of an upper photoactive layer with better morphology. Further, the O-NiAc layer can decrease the series resistance (Rs) and increase the parallel resistance (Rp) of the devices, inducing enhanced Vocin comparison with the as-prepared NiAc-buffered control devices without UVO treatment. For PSCs based on the P3HT:PCBM system, Vocincreases from 0.50 to 0.60 V after the NiAc buffer layer undergoes UVO treatment. Similarly, in the P3HT:ICBA system, the Vocvalue of the device with a UVO-treated NiAc buffer layer increases from 0.78 to 0.88 V, showing an enhanced power conversion efficiency of 6.64%.

A simple but efficient method has been first developed for the solution preparation of CrOxas anode buffer layer for polymer photovoltaic cells. The chromium acetylacetonate precursor can be transformed into CrOxupon thermal annealing at ∼60 °C, followed by ultraviolet-ozone treatment. The leakage current of the device with the CrOxanode buffer layer was decreased, and short-circuit current density (Jsc) was significantly increased in comparison with the device with the traditional poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) buffer layer. By analyzing the current density–voltage characteristics of the device, it is found that the CrOxanode buffer layer can simultaneously decrease the series resistance and increase the parallel resistance of the device, in comparison with the device with PEDOT:PSS anode buffer layer. For the cells based on poly(3-hexylthiophene) (P3HT) as donor and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) as acceptor, the power conversion efficiency (PCE) can be improved from 3.71% (with PEDOT:PSS buffer) to 4.27% via introduction of CrOxbuffer layer. The PCE of the device based on P3HT as donor and indene-C60-bisadduct (ICBA) as acceptor with CrOxanode buffer layer was further increased from 6.08 (with PEDOT:PSS buffer) to 6.55%. The results indicate that CrOxis a promising anode buffer layer for efficient and stable polymer solar cells.

Highly efficient polymer solar cells (PSCs) are demonstrated by introducing environmentally friendly CuOxas hole extraction anode buffer layer. The CuOxbuffer layer is prepared simply via spin-coating 1,2-dichlorobenzene solution of Copper acetylacetonate on the ITO substrate and thermal transformation (at 80 °C) in air. Remarkable improvements in the open-circuit voltage (Voc) and short-circuit current density (Jsc) of the PSCs could be achieved upon the introduction of CuOxbuffer layer. The study about the effect of CuOxinterfacial layer on the device resistances demonstrates that insertion of CuOxlayer can decrease the whole resistance of the PSCs. For the devices based on P3HT:PCBM, the power conversion efficiency (PCE) was increased from 2.8% (the reference device without buffer layer) to 4.1% via introduction of CuOxhole extraction layer. The PCE of the PSC was further increased to 6.72% when ICBA used as an alternative acceptor to PCBM. The much higher PCE of 7.14% can be achieved by adopting PBDTTT-C, a low band gap conjugated polymer, as donor material. The results demonstrate that CuOxhas great potential as a hole extraction material for highly efficient PSCs.

An integrated device architecture was constructed via vertical combination of planar and bulk heterojunctions by solution processing, where a cross-linked D-A copolymer (PBDTTT-Br25) was inserted between a PEDOT:PSS layer and the blended photoactive layer. PBDTTT-Br25 can readily undergo photo crosslinking to form an insoluble robust film via ultraviolet irradiation after solution–deposition, which enables the subsequent solution processing of a photoactive layer on the robust surface. The insertion of a pure PBDTTT-Br25 layer to build an integrated heterojunction could provide an additional donor/acceptor interface, which enables hole transport to the anode without interruption, thereby reducing the charge carrier recombination probability. The power conversion efficiency (PCE) of the polymer solar cell (PSC) with the integrated architecture reaches 5.24% under an AM1.5G illumination of 100 mW/cm2, which is increased by 65%, in comparison with that of the reference single heterojunction device (3.17%), under the same experimental conditions.

We report efficient and stable polymer solar cells (PSCs) based on poly(3-hexylthiophene) and various fullerene derivatives using solution processed, cost effective molybdenum oxide (s-MoOx) as an anode interfacial layer. The chemical structure of the obtained s-MoOxwas characterized by FTIR and XPS. The s-MoOxlayer exhibits high light transmittance and effective hole collection properties. The PSCs with the s-MoOxanode buffer layer show enhanced performance in comparison with PEDOT:PSS modified devices. The power conversion efficiency of the PSC based on P3HT:IC70BA with the s-MoOxanode buffer layer reached 6.57% under an illumination of AM1.5G at 100 mW cm−2. In addition, compared with PEDOT:PSS modified devices, PSCs with the s-MoOxanode buffer layer exhibit a much superior stability and longer lifetime.

TiO2films with controlled macroporous structures have been prepared from the precursor solution containing photomonomer dipentaerythritol pentaacrylate by a photopolymerization-induced phase-separation method (PIPS) in the absence of any surfactant and colloidal templates. The gel TiO2film deposited from the precursor solution by dip-coating was irradiated with the ultraviolet light for some time. During the irradiation process, the polymerization of the photomonomer was induced, which resulted in the phase-separation in the film system. At the end of the polymerization reaction, two phases existed in the film, one was the emerging polymer rich phase, and another was the residual monomer-TiO2oligomer-rich phase. After heat-treatment at 600 °C, the entire polymer decomposed and a well-defined interconnected macroporous TiO2films could be obtained. X-ray diffraction, scanning electron microscopy, atomic force microscopy, thermogravimetric, and differential thermal analysis were used to characterize the macroporous TiO2films. The results showed that the macroporous texture could be tuned by changing the composition of the precursor solution and the type of the reactive monomer. Polyvinylpyrrolidone was introduced into the system to slow the solvent evaporation. Highly macroporous TiO2films prepared by the PIPS method exhibited much higher photocatalytic activity for the decomposition of methylene blue dye than the dense TiO2film.

A new kind of fluorenonearylamine derivatives possessing vagarious red-emitting aggregation-induced emission (AIE) characteristics was reported for the first time. On the basis of theoretical calculations and experimental results, the AIE was found to originate from the unique dimer (excimer) specifically in the aggregates. In the crystals of both compounds, every two molecules are bond together by intermolecular O···H or C···C bonds to form particular dimers. In virtue of their nice solid-state red fluorescence, nondoped red-light OLEDs based on these AIE-active materials were fabricated. The devices exhibited low turn-on voltages of about 3 V, luminescence of 14135 and 4813 cd m-2, and efficiencies of 1.40 and 0.35 lm W-1based on the two materials. The results demonstrated that such AIE-active materials are promising candidates for nondoped red emission OLED applications.

Aggregation induced emission (AIE) is an amazing property for light emitting materials and has attracted much attention. Here, we report a new kind of AIE materials:  fluorenone derivates 2,7-dip-tolyl-fluorenone (DTFO) and 2,7-bis(4-(tert-butylthio)phenyl)-fluorenone (DSFO). Strong light emissions with a large Stokes shift and long lifetime in the solid state originate from the formation of excimers. The crystal structure of DSFO shows that every two molecules are bound together even in the ground state by intermolecular hydrogen bonds and form a particular dimer. When this dimer is excited, it turns into an excimer without arrangement adjustment and likewise without repulsive interactions when the excimer decays back to the dimer; so, the nonradiative decay pathways that exist in common excimers are greatly reduced and thus induce a strongly enhanced luminescence in the solid state. OLED devices employing DTFO as light emitting layers are fabricated and evaluated.