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Trans-Eurasian cultural and genetic exchanges have significantly influenced the demographic dynamics of Eurasian populations. The Hexi Corridor, located along the southeastern edge of the Eurasian steppe, served as an important passage of the ancient Silk Road in Northwest China and intensified the transcontinental exchange and interaction between populations on the Central Plain and in Western Eurasia. Historical and archeological records indicate that the Western Eurasian cultural elements were largely brought into North China via this geographical corridor, but there is debate on the extent to which the spread of barley/wheat agriculture into North China and subsequent Bronze Age cultural and technological mixture/shifts were achieved by the movement of people or dissemination of ideas. Here, we presented higher-resolution genome-wide autosomal and uniparental Y/mtDNA SNP or STR data for 599 northwestern Han Chinese individuals and conducted 2 different comprehensive genetic studies among Neolithic-to-present-day Eurasians. Genetic studies based on lower-resolution STR markers via PCA, STRUCTURE, and phylogenetic trees showed that northwestern Han Chinese individuals had increased genetic homogeneity relative to northern Mongolic/Turkic/Tungusic speakers and Tibeto-Burman groups. The genomic signature constructed based on modern/ancient DNA further illustrated that the primary ancestry of the northwestern Han was derived from northern millet farmer ancestors, which was consistent with the hypothesis of Han origin in North China and more recent northwestward population expansion. This was subsequently confirmed via excess shared derived alleles in f3/f4 statistical analyses and by more northern East Asian-related ancestry in the qpAdm/qpGraph models. Interestingly, we identified one western Eurasian admixture signature that was present in northwestern Han but absent from southern Han, with an admixture time dated to approximately 1000 CE (Tang and Song dynasties). Generally, we provided supporting evidence that historic Trans-Eurasian communication was primarily maintained through population movement, not simply cultural diffusion. The observed population dynamics in northwestern Han Chinese not only support the North China origin hypothesis but also reflect the multiple sources of the genetic diversity observed in this population.

Modification of twin boundaries has been deemed as a potential strategy to achieve high strength in combination with good ductility for many engineering alloys. Herein, we report a unique Li cluster segregation phenomenon in coherent contraction twin boundaries of Mg alloys. The structures at the atomic scale have been investigated by transmission electron microscopy. Meanwhile, the driving force for segregation and strengthening mechanisms have been elucidated by first-principles calculations and molecular dynamics simulations, respectively. Experimental results show that the segregated Li cluster with a hexagonal close-packed structure is coherent with a contraction twin. Subsequently, theoretical calculations reveal that the Li cluster is prone to occupy the interface vacancy in the contraction twin boundaries, following which it grows along the twin boundaries preferentially. Finally, both dynamics simulations and experimental observations demonstrate that the formation of Li cluster in contraction twin boundaries can not only directly pin dislocation movement analogous to precipitation strengthening, but also improve the critical shear strain of contraction twin boundaries, inhibiting their deformation or widening. The finding of cluster segregation in twin boundaries also occurs in other systems, which might open an avenue for twin boundary engineering to tune the mechanical properties of metals and ceramics.

In this work, one 8-shaped metasurface (MS) is proposed, which consists of a square array of 8-shaped conducting patches printed on a grounded dielectric substrate and covered by a top dielectric layer. Because the MS is symmetric with respect to both the x- and y-axes, and the phase difference between the reflection coefficients rxx and ryy is close to + 90° in an ultra-wide frequency band, it can be used as an ultra-wideband linear-to-circular polarization converter. Simulation results show that the MS can realize high-efficiency and ultra-wideband linear-to-circular polarization conversion under both u- and v-polarized incidences; the axial ratio (AR) of the reflected wave is below 3 dB in the ultra-wide frequency band of 6.45–24.20 GHz, which is corresponding to a relative bandwidth of 116%; in addition, the polarization conversion rate (PCR) can be maintained larger than 99.5% in the frequency range of 6.78–23.70 GHz, which occupies 95.3% of the 3 dB-axial-ratio-band. Finally, an experimental verification is carried out, a good agreement between the experimental and simulation results is observed.

Direct asymmetric three-component Mannich reaction involving simple ketones (such as cyclohexanone, acetone, and acetophenone) as donors and catalyzing by silver tartaric acid-derived phosphate was realized to afford a series of optically active β-amino-ketone derivatives in high yields (up to 96%) and good-to-high enantioselectivities (up to 97%) with moderate-to-good diastereoselectivities. This is the first example of direct catalytic asymmetric three-component Mannich reaction via a chiral counteranion-directed strategy.

Electromagnetic wave absorbing materials which are low in cost and light weight are highly desirable, especially if they can be easily manufactured. A special Fe2O3 nanotubes /reduced graphene oxide (RGO) composite sponge with a 3D (three dimensional) plus 2D (two dimensional) structure was produced. The Fe2O3 nanotubes /RGO composite sponge exhibits excellent microwave absorption capacity. Different amounts of Fe2O3 nanotubes in the RGO sponge work well in improving absorption effectiveness. Specifically, by using a small amount of Fe2O3 nanotubes, the desired absorption bandwidth gets to 8.7 GHz and obtains the best attenuation property among other samples tested, and with a moderate number of Fe2O3 nanotubes added which exhibits an outstanding degree of impedance matching performance. A large amount of Fe2O3 nanotubes will narrow down the desired absorption bandwidth, but it will enhance the minimum reflection loss. These excellent performances of the composites originate from the altered dielectric constants, scattering parameters and the unique multi-dimensional structure. A good microwave absorber should have a good impedance matching performance with an effective attenuation property at the same time. It can be concluded that having low S11 value is expected to have a good matching performance while S21 value can be a sign of microwave dissipation ability.

Metal sublimation plays a crucial role in understanding natural phenomena, purification and advanced manufacturing. Herein, we report anomalous sublimation passivation of nanotwinned silver particles under e-beam irradiation through in situ transmission electron microscopy, wherein the sublimation velocity is reduced by three-quarters due to the formation of five-fold twins. Theoretical calculations reveal that this sublimation passivation mechanism is mainly related to the increment in sublimation energy by the presence of twin boundaries.

In this paper, an ultra-wideband circular polarization (CP) maintaining reflector is proposed based on an anisotropic metasurface, which is an orthogonal anisotropic structure with a pair of symmet...

In order to find low-toxic light-absorbing materials for perovskite solar cells, the electronic structures and optical absorption spectra of doped perovskites CsPb₁–ₓMₓI₂Br (M = Ge, Sn, Sr, and Cu) have been investigated with the first-principles method. Ge- and Sn-doped perovskites display monotonously decreased band gaps with increasing x, opposite to Sr- and Cu-doped ones. Different from group IV Ge and Sn elements, Sr and Cu dopants show distinct electronic characteristics, that is, weak interaction with halogens because of the d orbitals splitting in octahedral complexes and unique density of states and band-decomposed charge densities. Meanwhile, Ge, Sn, and Cu dopants prefer substituting Pb sites in the CsI-terminated surfaces based on thermodynamic consideration, and the dopants accumulating on surfaces will deteriorate the optical absorption of perovskites based on the comparison of the absorption spectra of various doped structures. Therefore, this study provides a theoretical insight into the declined absorption spectra with the increasing concentration of dopants in experimental observations.

Obtaining an ideal ferroelectric photovoltaic (FE-PV) material with a narrow bandgap and a large ferroelectric polarization value can enable us to achieve great practical FE-PV performance. By the introduction of sulfur into the tetragonal BiCoO3 perovskite with a C-type antiferromagnetic ordering, it is found that the bandgap of BiCoO2S decreases significantly (about 1.2 eV) while maintaining a large polarization value (about 1.86 C m−2) that is similar to the value of 1.793 C m−2 of BiCoO3. Most noteworthy is that the optical absorption of BiCoO2S is remarkably higher than those of BiCoO3 and other FE-PV materials. The decrease of the BiCoO2S bandgap originates from the movement of Co 3d states to a low-energy position due to the reduction of the Co ionicity when the less electronegative sulfur is introduced into BiCoO3 to substitute oxygen. The narrow bandgap and the high optical absorption of the BiCoO2S films grown on different substrates are favorable for FE-PV applications. In addition, the bandgap of BiCoO2S can be modulated by the doping amount of sulfur, which can help us fabricate multilayer FE-PV devices based on different bandgaps from different layers.

Since its discovery ferroelectricity has been an intriguing phenomenon in materials science and is usually observed in a single ferroelectric material. In this study, it is shown that ferroelectriciy can also occur at the interface between two non-ferroelectric materials, a polymer and silicon, and interfacial ferroelectric-like behavior is demonstrated. Sulfonic functional groups on the polymer establish electrochemically switchable dipoles, which are considered to be the origin of ferroelectric polarization and are observed in an atom-thick polar region at the interface. Above room temperature polarization hysteresis loops with long term stability, thermal stability, reliable switching reproducibility and long information retention directly on rigid and flexible silicon substrates are demonstrated. This exotic ferroelectric phenomenon extends polarization switching beyond singular materials and has the potential to advance the design of new ferroelectric devices.

Several 1,3,5-triaryl-1,5-diketones have been chemoselectively synthesized under solvent-free conditions. It was found that intramolecular weak bifurcated H-bonds interaction of aliphatic C–H group plays a decisive role in the structural arrangement of 3-(2,6-dichlorophenyl)-1,5-diphenylpentane-1,5-dione in a solid state resulting in significant impact on the corresponding bond lengths and dihedral angles.

Insertion/deletion (Indel) genetic markers have special features compared to other forensic-related markers, such as the low mutation rate and di-allelic markers with length polymorphism, playing an indispensable role in the forensic and population genetics, molecular anthropology and evolutionary biology. However, the genetic diversity, allelic frequency, forensic parameters and population genetic characteristics of the Indel markers in Hmong-Mien-speaking Guizhou Miao people are unclear due to the sparse sampling. Thus, we genotyped 30 forensic-related Indel markers in 311 unrelated healthy Miao individuals (149 females and 161 males) residing in the Guizhou Province in Southwest China using the Investigator DIPplex amplification system. All 30 Indels are in accordance with the no departures of Hardy-Weinberg equilibrium and linkage disequilibrium. The combined probability of discrimination and the probability of exclusion in Guizhou Miao population are 0.999999999948 and 0.9843, respectively. This observed ideal forensic parameter estimates indicate that this di-allelic Indel panel can be used as a supplementary tool in forensic retinue personal identification and complemented for autosomal STRs in the parentage testing in Miao population, especially used as the main tool in old or highly degraded samples in disaster victim identification. Eleven Indels show a high allele frequency difference between different continental populations and could be used as ancestry-informative markers in forensic ancestry inference. Phylogenetic relationships between Guizhou Miao and 68 worldwide populations based on the genetic polymorphisms of Indels are investigated via three different pairwise genetic distances, principal component analysis, multidimensional scaling analysis and phylogenetic relationship reconstructions. Analyses of the comprehensive population genetic relationship comparison reveal significant genetic differentiation of Chinese groups. Our results demonstrate that Guizhou Miao people are genetically closer related to the geographically adjacent populations, especially with Liangshan Yi, Guangxi Miao and Dong, but genetically distinct with Turkic-speaking populations. Comprehensive and precise genetic admixture and divergence history of Guizhou Miao and neighboring populations are needed to further investigate and reconstruct via high-density marker panel or whole-genome sequencing of modern or ancient Miao samples.

China, inhabited by over 1.3 billion people and known for its genetic, cultural and linguistic diversity, is considered to be indispensable for understanding the association between language families and genetic diversity. In order to get a better understanding of the genetic diversity and forensic characteristics of Tai-Kadai-speaking populations in Southwest China, we genotyped 30 insertion/deletion (InDel) markers and amelogenin in 205 individuals from Tai-Kadai-speaking Bouyei people using the Qiagen Investigator DIPplex amplification kit. We carried out a comprehensive population genetic relationship investigation among 14,303 individuals from 84 worldwide populations based on allele frequency correlation and 4907 genotypes of 30 InDels from 36 populations distributed in all continental or major subregions and seven linguistic phyla in China. Forensic parameters observed show highly polymorphic and informative features for Asians, although the DIPplex kit was developed focusing on Europeans, and indicate that this amplification system is appropriate to forensic personal identification and parentage testing. Patterns of InDel variations revealed by principal components analysis, multidimensional scaling plots, phylogenetic relationship exploration, model-based clustering as well as four pairwise genetic distances (Fst, Nei, Cavalli-Sforza and Reynolds) demonstrate significant genetic differentiation at the continental scale and genetic uniformity in Asia except for Tibeto-Burman and Turkic-speaking populations. Additionally, Tai-Kadai speakers, including Bouyei, Zhuang and Dong, share more genetic ancestry components than with other language speakers, and in general they are genetically very similar to Hmong-Mien-speaking populations. The dataset of Bouyei people generated in the present study is valuable for forensic identification and parentage tests in China.

Surface engineering of crystalline silicon (c-Si) is the core of Si-based semiconductor devices. The current commercially available c-Si solar cells achieve this by making use of a conventional thin dielectric film passivation system (TDFPS), including SiO2, Al2O3, SiNx:H and hydrogenated amorphous silicon (a-Si:H) in industry. However, the TDFPS requires high-vacuum and/or high-temperature conditions, which hinders efforts to further reduce the costs of device fabrication. A revolutionized approach to circumvent these issues involves the replacement of TDFPS with new material system which can also achieve high-quality passivation on c-Si surface. Here, we successfully establish and implement a functional group passivation system (FGPS) using a series of functional materials with a sulfonic functional group -SO3H, such as ‘poly(2-acrylamido-2-methylpropanesulfonic acid)’ (PAMPS) and ‘polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene, sulfonated, cross-linkable’ (PS-b-PERB), which can achieve a highly effective passivation on Si surface, resulting in power conversion efficiencies up to 20% when they are applied in the front surface engineering of interdigitated back contact (IBC) solar cells. Furthermore, the FGPS materials inherently allow passivation layer fabrication in lowtemperature and high-vacuum-free conditions. This work provides novel low-cost material strategies without compromise of performance for c-Si surface engineering in the future Si-based photovoltaics.

Based on the first-principles calculations, the influence of different geometry models on the theoretical results about the electronic properties of LaAlO3/SrTiO3 perovskite heterostructures has been studied. The results show that the superlattice model can indicate n-type conductivity of interfaces, but it is limited to describe the insulator-metal transition of heterostructures. The sandwich and thin film models with the vacuum layer can take into account the surface termination effect on the electronic properties of the interface. The AlO2 or LaO atomic layer as the outmost surface termination is selected during constructing the model, leading to the distinct electronic properties of the heterostructures. The build-in electric filed appears in the AlO2-terminated structure, whereas it does not exist in LaO-terminated structure. Therefore, the AlO2-terminated structure can give a clear description about the insulator-metal transition of heterostructure and the charge transfer mechanism. The build-in electric filed, the atomic rumpling and surface termination effect of perovskite materials codetermine the conductivity of interfaces. The results would be helpful to construct theoretical model and understand the novel electronic properties during investigating other perovskite heterostructures.

Objectives The Hui people are the adherents of Muslim faith and distributing throughout China. There are two contrasting hypotheses about the origin and diversification of the Hui people, namely, the demic diffusion involving the mass movement of people or simple cultural diffusion. Materials and methods We collected 621 unrelated male individuals from 23 Hui populations all over China. We comprehensively genotyped more than 100 informative Y-chromosomal single nucleotide polymorphisms and 17 Y-chromosomal short tandem repeats (STRs) on those samples. Results Co-analyzed with published worldwide populations, our results suggest the origin of Hui people has involved massive assimilation of indigenous East Asians with about 70% in total of the paternal ancestry could be traced back to East Asia and the left 30% to various regions in West Eurasia. Discussion The genetic structure of the extant Hui populations was primarily shaped by the indigenous East Asian populations as they contribute the majority part of the paternal lineages of Hui people. The West Eurasian admixture was probably a sex-biased male-driven process since we have not found such a high proportion of West Eurasian gene flow on autosomal STRs and maternal mtDNA.

The origin and diversification of Muslim Hui people in China via demic or simple cultural diffusion is a long-going debate. We here generated genome-wide data at nearly 700,000 single nucleotide polymorphisms (SNPs) from 45 Hui and 14 Han Chinese individuals collected from Guizhou province in southwest China. We applied principal component analysis (PCA), ADMIXTURE, f-statistics, qpWave, and qpAdm analysis to infer the population genetic structure and admixture history. Our results revealed the Guizhou Hui people have a limited amount of West Eurasian related ancestry at a proportion of 6%, but show massive genetic assimilation with indigenous southern Han Chinese and Tibetan or Tungusic/Mongolic related northern East Asians. We also detected a high frequency of North Asia or Central Asia related paternal Y-chromosome but not maternal mtDNA lineages in Guizhou Hui. Our observation supports the cultural diffusion has played a vital role in the formation of Hui people and the migration of Hui people to southwest China was probably a sex-biased male-driven process.

Underwater sonar objective detection plays an important role in the field of ocean exploration. In order to solve the problem of sonar objective detection under the complex environment, a sonar objective detection method is proposed based on dilated separable densely connected convolutional neural networks (DS-CNNs) and quantum-behaved particle swarm optimization (QPSO) algorithm. Firstly, the dilated separable convolution kernel is proposed to extend the local receptive field and enhance the feature extraction ability of the convolution layers. Secondly, based on the linear interpolation algorithm, a multisampling pooling (MS-pooling) operation is proposed to reduce the feature information loss and restore image resolution. At last, with contraction-expansion factor and difference variance in the traditional particle swarm optimization algorithm introduced, the QPSO algorithm is employed to optimize the weight parameters of the network model. The proposed method is validated on the sonar image dataset and is compared with other existing methods. Using DS-CNNs to detect different kinds of sonar objectives, the experiments shows that the detection accuracy of DS-CNNs reaches 96.98% and DS-CNNs have better detection effect and stronger robustness.

For filler-polymer systems, the ultimate importance of interfacial interactions between fillers and polymers lies in improving morphological developments and properties of composites. In this work, sepiolite fiber (SEP)/polyoxymethylene (POM) is formulated through melt extrusion processing, with the aim of promoting the crystallization and overall performance of POM. Results show that hydrogen bonding prevails between SEP hydroxyls and POM C-O-C groups. Thus SEP fibers are dispersed uniformly in the POM matrix due to interfacial interactions between these two components. During the isothermal crystallization process, POM nuclei originate and grow on the SEP surface, resulting in decreasing spherulite sizes and facilitating the POM crystallization. Meanwhile, the crystallinity of POM is increased from 48.3% to 54.1% by the addition of 5 wt% SEP. Noteworthily, mechanical and thermostability performances of SEP/POM composites have been improved considerably by means of sufficient interfacial interactions, enhanced crystallization, and favorable physical properties of SEP. Maximum values of the tensile strength and modulus at 3.0 wt% SEP loading can reach 66 MPa and 2022 MPa, respectively higher than those of neat POM.

Crystalline silicon (c-Si) solar cells remain dominant in the photovoltaic (PV) market because of their cost-effective advantages. However, the requirement for expensive vacuum equipment and the power-hungry thermal budget for surface passivation technology, which is one of the key enablers of the high performance of c-Si solar cells, impede further reductions of costs. Thus, the omission of the vacuum and high-temperature process without compromising the passivation effect is highly desirable due to cost concerns. Here, we demonstrate a vacuum-free, room-temperature organic Nafion thin-film passivation scheme with an effective minority carrier lifetime (τeff) exceeding 9 ms on an n-type c-Si wafer with a resistivity of 1–5 Ω·cm, corresponding to an implied open circuit voltage (iVoc) of 724 mV and upper-limit surface recombination velocity (SRV) of 1.46 cm/s, which is a level that is in line with the hydrogenated amorphous Si film-passivation scheme used in the current PV industry. We find that the Nafio...

An organic semiconductor composite thin film, 5,6,11,12-tetraphenylnaphthacene:dimethyl sulfoxide (rubrene:DMSO), is fabricated by dissolving rubrene powder into the DMSO solvent to form the precur...

The magnesium hydrogenation issue poses a serious obstacle to designing strong and reliable structural materials as well as offering a safe alternative for hydrogen applications. Understanding phase transformation of magnesium under hydrogen gas plays an essential role in developing high-performance structural materials and hydrogen-storage materials. Herein, we report in-situ atomic-scale observations of phase transformation of Mg and Mg-1 wt % Pd alloy under hydrogen conditions in an aberration-corrected environmental transmission electron microscope. Compared with the magnesium hydrogenation reaction, the magnesium oxidation reaction predominately occurs at room temperature even under pure hydrogen gas (99.9%). In comparison, magnesium hydrogenation is readily detected in the interface between Mg and Mg6Pd, due to the catalytic role of Mg6Pd. Note that the nanoscale MgH2 compound transfers into MgO spontaneously, and the interface strain remarkably varies during phase transformation. These atomic-level...

Ecosystem sustainability is the basis for life, economic and social sustainability. The energy metabolism of an ecosystem has long been a focus area in the scientific community because it determines the productivity, sustainability and development of ecosystem. This study applied emergy analysis to explore the metabolism of maize ecosystems under different environmental conditions; to investigate its energy input, environmental pressure and sustainability; and to understand the maintenance mechanism of the general ecosystem based on the China statistical data of 2014. Results showed that the sum of renewable natural resources ranged from 0.62 × 10 14 seJ/ha in Xinjiang to 6.34 × 10 14 seJ/ha in Guangxi; the sum of nonrenewable natural resources ranged from 3.95 × 10 14 seJ/ha for Henan to 9.46 × 10 14 seJ/ha for Jilin; the sum of purchased renewable resources ranged from 2.97 × 10 14 seJ/ha for Heilongjiang to 26.14 × 10 14 seJ/ha for Gansu; the sum of purchased nonrenewable resources ranged from 14.89 × 10 14 seJ/ha in Sichuan to 33.00 × 10 14 seJ/ha in Gansu. In addition, the environmental loading ratio in Xinjiang was the highest, followed by Ningxia (25.92), Gansu (24.77), Inner Mongolia (23.15), the lower values were 4.48, 4.21 and 4.00 for Guizhou, Chongqing and Guangxi, respectively; similarly, the emergy sustainability index in the provinces of southern China were higher than those in northwest of China. Above all, maize ecosystem is developed with a stronger competitive ability than other agricultural ecosystems, especially in the southern region of China, but also has a high environmental loading ratio. Furthermore, the proportion of natural and purchased emergy input ranged from 13.65% vs 86.35% in Xinjiang to 33.70% vs 66.30% in Heilongjiang, which were close to 30% vs 70%, 25% vs75%, 22% vs 78%, 20% vs 80% and 15% vs 85% for Northeast of China, Southwest of China, Loess Plateau, Huang-Huai-Hai Plain and Northwest of China respectively. Our study demonstrates that the natural energy in the maize ecosystem influenced the quantity and proportion of purchased energy. Different combinations of natural and purchased emergy were coupled to maintain the same ecosystem under the different environmental conditions. Its recommendation is to consider changing the crop production systems or artificial energy inputs in different regions based on differences in natural factors in order to make more efficient use of resources, reduce the use of chemical fertilizers, and promote the sustainability of ecosystems.

Heterojunction architectures become a major trend in the development of high power conversion efficiency (PCE) c-Si solar cell in recent. However, NiO as a prevailing material in other application is not favored in c-Si solar cells. In this study, a novel solar cell architecture using nonstoichiometric p-type NiO thin films as a hole-selective, dopant-free contact to n-type crystalline silicon (n-Si) is successfully fabricated. We achieved a power conversion efficiency (PCE) of 4.3% in the pure NiO/n-Si heterojunction solar cell, which is the first case to be reported. Further Cu-incorporation enhanced the work function and conductivity of NiO films (NiO:Cu, for short), increasing built-in potential and favoring hole transport in the NiO:Cu/n-Si heterojunction, which results in a record PCE of 9.1% among all bulk-like NiO/Si heterojunction solar cells. Analysis of the spectra of Cu 2p and Cu LMM Auger lines, measured by X-ray photoelectron spectroscopy (XPS), shows that the fabricated NiO:Cu film is a mixture of metallic Cu, Cu2O and CuO multi-phase coexistence. Among these species, the proper Cu incorporation contributes the improvement of acceptor concentration due to the dominant phase of Cu+, but the excessive Cu incorporation creates defect states within the band gap, increasing recombination and deteriorating interface quality, which leads to S-shape current density-voltage (J-V) characteristics.

In this study, MgNd intermetallic is deposited as a thin film using magnetron sputtering. Ultraviolet photoelectron spectroscopy (UPS) is employed to determine the work function of the MgNd thin film. It is found that the MgNd thin film has a low work function of 3.5 eV, leading to its application in hybrid poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS)/n-Si solar cells as a back surface field (BSF) material. By introducing a MgNd thin film into the back Si/electrode interface of a hybrid solar cell, obvious improvements in the open circuit voltage (Voc) and fill factor (FF) of the device are observed, leading to an increase by more than 26% in power conversion efficiency (PCE). Temperature-dependent current density–voltage (J-V) and Voc-light intensity measurements demonstrate that the introduction of a MgNd thin layer increases the built-in voltage at the rear interface and decreases the recombination current in the device. These improvements are attributed to the efficacy of the MgNd thin film as a BSF by reducing minority carrier recombination and enhancing majority carrier transport.

The most important aspect in the development of Si-based photovoltaic technologies is the passivation of the Si wafer surface. Here, we show that Poly(3,4-ethylthiophene):polystyrenesulfonate (PEDOT:PSS) thin films, frequently used in organic/inorganic hybrid solar cells as emitter layers, provide an excellent surface passivation with a millisecond (ms) level effective minority carrier lifetime ( τ eff ). More importantly, we find that this passivation effect is dominated by the PSS species in PEDOT:PSS rather than PEDOT ones. The PSS thin film passivation yields a high τ eff of 9.4 ms on a high-resistivity Si wafer. The interface nature of PSS/Si is unveiled by the X-ray photoelectron spectroscopy and first-principles total-energy calculations together. An electrochemical passivation mechanism is clarified: the Si sub-oxides form at PSS/Si interface by the electrochemical grafting O groups in PSS onto Si surface, which can be controlled by injecting holes or electrons into the Si surface, leading to a switchable interface state between oxidation and deoxidation. To examine the application of the passivation strategy in real devices, we develop a polymer-passivated both-sides Si heterojunction solar cell with light-induced enhancement of photovoltaic performances, which is consistent with the light-induced enhancement of τ eff .

Two-dimensional MXene materials with proper direct-band gap are especially desirable for photoelectric applications. Herein a new scandium-based carbide MXene (ScNbCO2) with direct band gap of ∼1.40 eV has been predicted by doping Nb transition metal and strain in terms of density-functional theory. The Nb-doping changes into direct band gap of 1.84 eV from indirect band gap of 2.96 eV of Sc2CO2. Attractively, the direct band gap of ScNbCO2 of ∼1.40 eV is further attained by stain effect. Especially, an increase of ∼20 times is achieved in the case of 3% uniaxial ScNbCO2. It reveals that these metal-doping MXene materials are promising to develop new light-electron conversion components.

The sustainability of ecosystem productivity and rules governing ecosystem development are important topics of scientific research. The emergy approach is an effective method for investigating these topics, especially when used to evaluate systems that have developed under the same environmental conditions, such as climate and soil. In this paper, emergy differences between terrestrial ecosystems were studied in Guyuan County, a region representative of the agro-pastoral ecotone in Hebei Province, China. A combination of field tests and a questionnaire survey were carried out between June and August 2015. The ecosystems studied included natural grassland, artificial grassland, field crops and commercial crops. These four ecosystems were further subdivided into a total of ten ecosystems. Natural grassland was divided into free-grazing and mowed ecosystems; artificial grassland consisted of oat, Chinese leymus and corn silage; field crops included naked oats, flax and wheat; and commercial crops consisted of cabbage and potatoes. The results showed that the rain input of 4.78 × 1014 seJ/ha/yr constituted the highest renewable natural resource emergy and that the purchased emergy inputs of the ten ecosystems ranged from 3.53 to 147.67 × 1014 seJ/ha/yr. Natural resource emergy input was the basic power to maintain the ecosystem, and purchased emergy input was the direct cause of the development of the ecosystems. Groundwater was the most important non-renewable purchased energy for the production of economic crops. The emergy investment ratios (EIR) for potatoes (27.81) and cabbage (19.03) were higher than those of the other ecosystems, but mowed and artificial Chinese leymus grassland had the higher emergy self-sufficiency rates (ESR). Natural grassland, artificial Chinese leymus grassland and traditional grain crops had a low environmental load and high sustainability, whereas potatoes and cabbage had a high environmental load and low sustainability. Overall, rain-fed artificial grassland has a high development potential from the perspective of environment and productivity.

Surface group modification and functionalization of two-dimensional materials in many cases are deemed as effective approaches to achieve some distinctive properties. Herein, we present a new nanoflower-shaped TiO2/C composite which was synthesized by in situ alcoholysis of two-dimensional layered MXene (Ti3C2(OHxF1–x)2) in a dilute HF solution (0.5 wt %) for the first time. Furthermore, it is demonstrated that it bestows a strong catalytic activity for the dehydrogenation of NaAlH4. The results show that the NaAlH4 containing 10 wt % A0.9R0.1–TiO2/C (containing 90% anatase TiO2 and 10% rutile TiO2) composite merely took ∼85 min to reach a stable and maximum dehydrogenation capacity of ∼3.08 wt % at 100 °C, and it maintains stable after ten cycles, which is the best Ti-based catalyst for the dehydrogenation of NaAlH4 reported so far. Theoretical calculation confirms that this C-doping TiO2 crystals remarkably decreases desorption energy barrier of Al–H bonding in NaAlH4, accelerating the breakdown of Al–H...

Understanding the oxidation process of active metals plays a crucial role in improving their mechanical/oxidation properties. Using in situ environmental transmission electron microscopy and density-functional theory, we firstly clarify the oxidation process of single-crystal Mg at the atomic scale by using a new double-hole technique. A unique incipient interval-layered oxidation mechanism of single-crystal Mg has been confirmed, in which O atoms intercalate through the clean (21[combining macron]1[combining macron]0) surface into the alternate-layered tetrahedral sites, forming a metastable HCP-type MgO0.5 structure. Upon the increased incorporation of oxygen at the neighboring interstitial sites, the HCP-type Mg-O tetrahedron structure sharply transforms into the FCC-type MgO oxide. In addition, a typical anisotropic growth mechanism of oxides has been identified, wherein it involves two routes: the epitaxial growth of the MgO layer and the inward migration of the MgO/Mg interface. The whole oxidation rate of single-crystal Mg is mostly determined by the inward migration rate of the MgO/Mg interface, which is about six times higher than that of the epitaxial growth rate of the MgO layer along the same orientation planes. Moreover, the inward migration rate of the (020)MgO‖(011[combining macron]0)Mg interface is about twice as large as that of the (200)MgO‖(0002)Mg interface. This continuous oxide growth is mainly related to the defects in the MgO layer, which builds effective channels for the diffusion of O and Mg atoms. The in situ double-hole observations together with theoretical calculations provide a potential trajectory to probe the oxidation fundamentals of other active metals.

Abatement effort can bring about different consequences towards emissions, which is mainly due to the mechanism within the abatement investments. In this paper, the study aims to study in more depth how differentiated evanescent and inertia abatement investments should be allocated to achieve carbon reduction, and also to show that the abatement path and costs differ sensibly between these two allocations. Inertia performance is the critical determinant to this distinction, however which can be influenced deeply by the overestimation of the economic growth. The work confirms the results in theory that the abatement trends differentiated between the evanescent and the inertia case, in which the former is more likely to be an early-move action and however the latter tends to suffer from the converted burden with the underassessment of the growth. Turning to the numerical method, the work gauges the magnitude of the differentiated abatement efforts as well as the burden shifting between them. These qualitative results also confirm our ratiocination, which further help to analyze some intricate disturbances beyond the power of theory. Also we can find that the total cost is increasing due to the introduction of the operating cost, and the accumulated capital of the inertia abatement is more smooth and weighs less. The peak of the accumulated capital is dropping by 38%. Moreover, the evanescent abatement effort is more attractive than the basic case, which is risen universally by 22%. The study derives some policy implications for the ranking to the implementation of the abatement efforts and for incentive instruments to be set up at the industrial level.

The Xinjiang Uyghur Autonomous Region of China (XUARC) with 47 ethnic groups is a very colorful ethnic region of China, harboring abundant genetic and cultural diversity. The Kazakhs are the third largest ethnic group (7.02%) after Uyghur (46.42%) and Han (38.99%) in Xinjiang, but their genetic diversity and forensic characterization are poorly understood. In the current study, we genotyped 15 autosomal short tandem repeat (STR) loci and ten Y-STRs in 889 individuals (659 male and 230 female) collected from Kazak population of the Ili Kazak Autonomous Prefecture using AGCU Expressmarker 16 and 10Y-STR Kit (EX16 + 10Y). For autosomal STRs, we observed a total of 174 different alleles ranging from 6 to 34.2 repeat units and FGA showed the greatest power of discrimination (20 alleles) in Ili Kazakh population. We have not observed departures from Hardy-Weinberg equilibrium (HWE) after sequential Bonferroni correction and only found a minimal departure from linkage equilibrium (LE) for a very small number of pairwise combinations of loci. The combined power of exclusion (CPE) was 0.99999998395 and combined power of discrimination (CPD) was 99.999999999999999798%. For Y-STRs, we observed a total of 496 different haplotypes in these ten Y-STR loci. The gene diversities ranged from 0.5023 (DYS391) to 0.8357 (DYS385a/b). The overall haplotype diversity (GD) was 0.9985 with random matching probability (RMP) of 0.0015. The results of population genetic analysis based on both autosomal and Y-chromosome STRs demonstrated that the genetic affinity among populations is generally consistent with ethnic, linguistic, and continental geographical classifications.

The alkalization-intercalated MXene (Alk-MXene: Ti3C2(OH)2) has recently confirmed as a new and effective material for removing Pb heavy metal. Herein, taking into account of the complexity and diversity of MXenes, the Pb adsorption behavior of different MXenes with the highest valuable applied structure of M2X (OH)2 (M = Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and X = C or N) has been systemically investigated by first principles calculations utilizing the generalized gradient approximation with the density functional theory, which paves a desirable trajectory for the applications of MXenes. Basically, the formation energies of M2N(O2H2−2xPbx) are lower than those of M2C(O2H2−2xPbx), suggesting the substitution of N is more effective for the Pb adsorption in contrast to C due to the different valence electron numbers between C and N atoms. In addition, the results show that the Ti2C(OH)2 is the most favorite one for the lowest mass fraction to lead removal. Notably, both Sc2C(OH)2 and Zr2C(OH)2 structures don’t have the ability of Pb removal. The kinetics of the lead removal was elucidated on the variation of potential wells by virtue of the density of states and electron localization function.

A new MXene/Ag composite was synthesized by direct reduction of a AgNO3 aqueous solution in the presence of MXene (Ti3C2(OH)0.8F1.2). The as-received MXene/Ag composite can be deemed as an excellent anode material for lithium-ion batteries, exhibiting an extraordinary long cycle lifetime with a large capacity at high charge-discharge rates. The results show that Ag self-reduction in MXene solution is related to the existence of low-valence Ti. Reversible capacities of 310 mAh·g(-1) at 1 C (theoretical value being ∼320 mAh·g(-1)), 260 mAh·g(-1) at 10 C, and 150 mAh·g(-1) at 50 C were achieved. Remarkably, the composite withstands more than 5000 cycles without capacity decay at 1-50 C. The main reasons for the long cycle life with high capacity are relevant to the reduced interface resistance and the occurrence of Ti(II) to Ti(III) during the cycle process.

Based on first-principles calculations, the electronic properties of n-type LaAlO3/SrTiO3 (LAO/STO) interfaces with LaO and AlO2 terminations were investigated. Thermodynamic analysis shows that the AlO2-terminated and LaO-terminated LaAlO3 surfaces are preferably formed under O-rich and O-poor conditions, respectively. We found that there are two polarization fields in heterostrucutres: one is the build-in polarization field induced by alternating LaO+1 and AlO2−1 layers and another is the strain-induced additional polarization field only existing in relaxed structures. The two polarization fields have a distinct influence on the electronic structures of interfaces. In this work, the influences of oxygen vacancies and cation defects at different sites on the conduction mechanism were analyzed in detail. The results indicate that point defects affect the electronic states of interfaces by two ways: providing or accepting electrons, and disturbing the internal polarization field. Approaching the interface, the defects tend to play the former role. Moreover, the calculations show that under O-rich condition, the reduced oxygen vacancies and the improved cation vacancies spontaneously formed at the interface deteriorate the n-type conductivity. The present results provide a theoretical guidance to utilize the effects of surface termination and point defects to tune the conductivity of perovskite heterostructures.

In this work, an ultra-wideband and high-efficiency reflective polarization converter is proposed based on an orthotropic anisotropic metasurface for both linear and circular polarized waves, which is a symmetric structure with a pair of mutually perpendicular symmetric axes. Both the simulated and measured results show that the polarization converter can realize linear polarization conversion at x- and y-polarized incidences in the frequency range from 8.77 to 24.71 GHz, which is corresponding to a 95.2% relative bandwidth; moreover, it can keep the handedness of the reflected wave the same as that of the incident wave in this band and realize reflection-type circular polarization conversion at circular polarized (CP) incidence. We have explained the root cause of these polarization conversions, and made it clear that it is just the symmetry of the metasurface structure which makes the magnitude of co-polarized reflection coefficient at CP incidence equal to that of the cross-polarized reflection coefficient at x- and y-polarized incidences, thus it is shown that the previously proposed various reflective linear polarization converters based on orthotropic anisotropic metasurfaces can all realize reflection-type circular polarization conversion.

The atomic structure and electronic properties of Sn/Pb mixed organometal halide perovskites were investigated by using first-principles method. The structure-dependent band gap behaviour of tetragonal and pseudocubic MASnxPb1−xI3 ( 0 ⩽ x ⩽ 1 ) was emphasized. The configurations with two or more adjacent Sn octahedra in the same layer inducing less tilting of neighbouring octahedra have the lower formation energy. For tetragonal or pseudocubic MASn0.5Pb0.5I3, the configuration of Sn octahedra layer alternating with Pb octahedra layer leads to elongated octahedra along the stacking direction, which stimulates the remarkable band splitting due to anomalous hybridization of Pb or Sn orbitals and I orbitals. This arrangement mode of Sn octahedra produces the narrowest band gap of Sn/Pb binary perovskite, whereas the separated and dispersed Sn octahedra significantly broaden the band gap. The results are helpful to understand the abnormal band gap behaviour in Sn/Pb binary perovskite experiments.

Self-assembling has been confirmed as an effective pathway to achieve some unique properties. The recently developed two-dimensional transition metal carbides (termed MXene) provide more potential opportunities to modify the surfaces of layered materials relative to simple graphene. Here we describe a one-step method for preparing an urchin-like rutile TiO2–C (u-RTC) nano-composite with a high amount of (110) facets by in situ phase transformation of MXene (Ti3C2(OH)0.8F1.2) under FeCl3 conditions. A layered anatase TiO2–C (l-ATC) nano-composite with a high percentage of (001) facets first forms, and then it changes into u-RTC due to the Fe(III) ion induction. The u-RTC displays a high Cr(VI) adsorption capacity of ∼225 mg g−1, which is higher than that of the primitive MXene (∼62 mg g−1) and the l-ATC precursor (∼11 mg g−1), owing to the inhibition of H2O molecule adsorption by bridging oxo groups in terms of the first principles calculations. Apart from the fact that the finding leads to a desirable aligned oxide-carbon material, this approach may set up a new trajectory to self-assemble functional surfaces of other MXene derivatives.

The development of ferroelectric photovoltaic (FE-PV) materials has been limited for a long time due to their large bandgap. Many strategies for lowering the bandgap have been suggested to promote FE-PV properties. The effects of magnetic ordering and B-site-cation ordering to lower the bandgap of FE-PV are investigated in this paper using first-principles calculations. Results show that the most stable structure of tetragonal Bi2FeCrO6 ([Formula: see text]-Bi2[Formula: see text] is the AS1 structure (Fe/Cr alternate stacking ordering) with C-type antiferromagnetic ordering (defined as AC-[Formula: see text]-Bi2FeCrO6), which has a small bandgap, suggesting that AC-[Formula: see text]-Bi2FeCrO6 is among the FE-PV materials with the highest application potential.

Li-CO2 batteries can not only capture CO2 to solve the greenhouse effect but also serve as next-generation energy storage devices on the merits of economical, environmentally-friendly, and sustainable aspects. However, these batteries are suffering from two main drawbacks: high overpotential and poor cyclability, severely postponing the acceleration of their applications. Herein, a new Co-doped alpha-MnO2 nanowire catalyst is prepared for rechargeable Li-CO2 batteries, which exhibits a high capacity (8160 mA h g-1 at a current density of 100 mA g-1 ), a low overpotential (≈0.73 V), and an ultrahigh cyclability (over 500 cycles at a current density of 100 mA g-1 ), exceeding those of Li-CO2 batteries reported so far. The reaction mechanisms are interpreted depending on in situ experimental observations in combination with density functional theory calculations. The outstanding electrochemical properties are mostly associated with a high conductivity, a large fraction of hierarchical channels, and a unique Co interstitial doping, which might be of benefit for the diffusion of CO2 , the reversibility of Li2 CO3 products, and the prohibition of side reactions between electrolyte and electrode. These results shed light on both CO2 fixation and new Li-CO2 batteries for energy storage.

A hysteresis loop of minority carrier lifetime vs voltage is found in polystyrenesulfonate (PSS)/Si organic-inorganic hybrid heterojunctions, implying an interfacial memory effect. Capacitance-voltage and conductance-voltage hysteresis loops are observed and reveal a memory window. A switchable interface state, which can be controlled by charge transfer based on an electrochemical oxidation/deoxidation process, is suggested to be responsible for this hysteresis effect. We perform first-principle total-energy calculations on the influence of external electric fields and electrons or holes, which are injected into interface states on the adsorption energy of PSS on Si. It is demonstrated that the dependence of the interface adsorption energy difference on the electric field is the origin of this two-state switching. These results offer a concept of organic-inorganic hybrid interface memory being optically or electrically readable, low-cost, and compatible with the flexible organic electronics.

Light-induced degradation has been identified to be a critical issue for most silicon-based solar cell technologies. This study presents an observation of an opposite light-induced enhancement (LIE) effect in photovoltaic performance in poly(3,4-ethylthiophene):polystyrenesulfonate/n-Si organic-inorganic hybrid solar cells. The reduced density of interface states under light soaking (LS) is found to be responsible for the LIE of the hybrid solar cells. An increased minor carrier lifetime under LS and a switchable photoluminescence intensity while applying a voltage bias are observed, providing evidence for the underlying physical mechanism.

In this work, a polymer thin film, polystyrenesulfonate (PSS), is employed in interdigitated back contact (IBC) solar cells as an anti-reflection (AR) coating and front surface passivation (SP) layer. It is found that PSS thin film is highly transparent and possesses a refraction index of about 1.5, and thus functions well as AR coating for Si wafer-based solar cells. An effective minority carrier lifetime of 2.3 ms is obtained on 1–5 Ω · cm n-type crystalline Si wafer with both sides symmetrically coated by PSS thin film, proving a good Si surface passivation by this polymer. An increase in power conversion efficiency is obtained when 150 nm-thick PSS thin film is coated on the front surface of IBC solar cells without any AR/SP layers, resulted from the increased short circuit current density and open circuit voltage. This work opens up a new approach using organic polymer thin film deposited with low temperature and vacuum-free technique as AR/SP multifunctional layer in Si solar cells.

Sodium-ion batteries are considered alternatives to lithium-ion batteries for energy storage devices due to their competitive cost and source abundance. However, the development of electrode materials with long-term stability and high capacity remains a great challenge. Here, this paper describes for the first time the synthesis of a new class of core–shell MAX@K2Ti8O17 by alkaline hydrothermal reaction and hydrogenation of MAX, which grants high sodium ion-intercalation pseudocapacitance. This composite electrode displays extraordinary reversible capacities of 190 mA h g−1 at 200 mA g−1 (0.9 C, theoretical value of ≈219 mA h g−1) and 150 mA h g−1 at 1000 mA g−1 (4.6 C). More importantly, a reversible capacity of 75 mA h g−1 at 10 000 mA g−1 (46 C) is retained without any apparent capacity decay even after more than 10 000 cycles. Experimental tests and first-principle calculations confirm that the increase in Ti3+ on the surface layers of MAX@K2Ti8O17 by hydrogenation increases its conductivity in addition to enhancing the sodium-ion intercalation pseudocapacitive process. Furthermore, the distorted dodecahedrons between Ti and O layers not only provide abundant sites for sodium-ion accommodation but also act as wide tunnels for sodium-ion transport.

In this work, a magnesium (Mg) thin film with a low work function is introduced to obtain a downward energy band at the rear surface of a hybrid solar cell to achieve the function of a back surface field (BSF) similar to the conventional n-n+ high-low junction, i.e., favouring the majority carrier transport and suppressing minority carrier recombination. The open circuit voltages (Voc) of the hybrid solar cells with the Mg BSF layer achieve a clear improvement over those containing only the conventional metal electrode (e.g., Ag), resulting in an increase in the power conversion efficiency (PCE) of the hybrid solar cells from 9.2% to 12.3%. The Suns-Voc measurement determined using a Sinton tool gives Voc as a function of light intensity and shows that Voc increases linearly with the light intensity for the solar cell with the Mg BSF but increases first and then stabilises for the cells without the Mg BSF. This result is attributed to a difference in back surface recombination, further confirming the effi...

The use of polystyrenesulfonate (PSS) thin films in a high-quality passivation scheme involving the suppression of minority carrier recombination at the silicon surface is presented. PSS has been used as a dispersant for aqueous poly-3,4-ethylenedioxythiophene. In this work, PSS is coated as a form of thin film on a Si surface. A millisecond level minority carrier lifetime on a high resistivity Si wafer is obtained. The film thickness, oxygen content, and relative humidity are found to be important factors affecting the passivation quality. While applied to low resistivity silicon wafers, which are widely used for photovoltaic cell fabrication, this scheme yields relatively shorter lifetime, for example, 2.40 ms on n-type and 2.05 ms on p-type wafers with a resistivity of 1–5 Ω·cm. However, these lifetimes are still high enough to obtain high implied open circuit voltages (Voc) of 708 mV and 697 mV for n-type and p-type wafers, respectively. The formation of oxides at the PSS/Si interface is suggested to ...