Free-standing ultrathin silicon wafers and solar cells through edges reinforcement.

Crystalline silicon solar cells with regular rigidity characteristics dominate the photovoltaic market, while lightweight and flexible thin crystalline silicon solar cells with significant market potential have not yet been widely developed. This is mainly caused by the brittleness of silicon wafers and the lack of a solution that can well address the high breakage rate during thin solar cells fabrication. Here, we present a thin silicon with reinforced ring (TSRR) structure, which is successfully used to prepare free-standing 4.7-µm 4-inch silicon wafers. Experiments and simulations of mechanical properties for both TSRR and conventional thin silicon structures confirm the supporting role of reinforced ring, which can share stress throughout the solar cell preparation and thus suppressing breakage rate. Furthermore, with the help of TSRR structure, an efficiency of 20.33% (certified 20.05%) is achieved on 28-µm silicon solar cell with a breakage rate of ~0%. Combining the simulations of optoelectrical properties for TSRR solar cell, the results indicate high efficiency can be realized by TSRR structure with a suitable width of the ring. Finally, we prepare 50 ~ 60-µm textured 182 × 182 mm2 TSRR wafers and perform key manufacturing processes, confirming the industrial compatibility of the TSRR method.

A Low-Noble-Metal Ru@CoMn2O4 Spinel Catalyst for the Efficient Oxidation of Propane.

Noble metals have become a research hotspot for the oxidation of light alkanes due to their low ignition temperature and easy activation of C-H; however, sintering and a high price limit their industrial applications. The preparation of effective and low-noble-metal catalysts still presents profound challenges. Herein, we describe how a Ru@CoMn2O4 spinel catalyst was synthesized via Ru in situ doping to promote the activity of propane oxidation. Ru@CoMn2O4 exhibited much higher catalytic activity than CoMn2O4, achieving 90% propane conversion at 217 °C. H2-TPR, O2-TPD, and XPS were used to evaluate the catalyst adsorption/lattice oxygen activity and the adsorption and catalytic oxidation capacity of propane. It could be concluded that Ru promoted synergistic interactions between cobalt and manganese, leading to electron transfer from the highly electronegative Ru to Co2+ and Mn3+. Compared with CoMn2O4, 0.1% Ru@CoMn2O4, with a higher quantity of lattice oxygen and oxygen mobility, possessed a stronger capability of reducibility, which was the main reason for the significant increase in the activity of Ru@CoMn2O4. In addition, intermediates of the reaction between adsorbed propane and lattice oxygen on the catalyst were monitored by in situ DRIFTS. This work highlights a new strategy for the design of a low-noble-metal catalyst for the efficient oxidation of propane.

Carbohydrazide-Assisted Morphology and Structure Controlling for Lead-Free Cs2AgBiBr6 Double Perovskite Solar Cells.

The stability and toxicity problems have haunted the development and applications of metal halide perovskite materials, for which the lead-free inorganic double perovskite Cs2AgBiBr6 has emerged as a promising substitute in recent years. However, poor film quality has severely limited its photovoltaic performance that could have been induced by some key factors such as high annealing temperature. Herein, we present a facile strategy to fabricate high-quality pinhole-free Cs2AgBiBr6 films with large grain sizes by introducing carbohydrazide (CBH) into the precursor. Detailed characterizations have shown that the carbonyl group (C═O) in CBH plays the critical role in coordinating with Ag+ and Bi3+ cations during the film formation process. As another consequence, the as-fabricated devices have exhibited significantly higher reproducibility for fabrication. By optimizing the amount of CBH, the power conversion efficiency (PCE) relatively increased 37 to 1.57%, which remained 95.0% in an ambient environment for a 1000-h test. Hopefully, this work could facilitate the current technologies in the exploration of high-performance lead-free perovskites such as Cs2AgBiBr6 and better understanding of the mechanism in the additive engineering as well.

Osa-miR162a Enhances the Resistance to the Brown Planthopper via α-Linolenic Acid Metabolism in Rice (Oryza sativa).

The brown planthopper (BPH) is the most serious pest causing yield losses in rice. MicroRNAs (miRNAs) are emerging as key modulators of plant-pest interactions. In the study, we found that osa-miR162a is induced in response to BPH attack in the seedling stage and tunes rice resistance to the BPH via the α-linolenic acid metabolism pathway as indicated by gas chromatography/liquid chromatography-mass spectrometry analysis. Overexpression of osa-miR162a inhibited the development and growth of the BPH and simultaneously reduced the release of 3-hexenal and 3-hexen-1-ol to block host recognition in the BPH. Moreover, knockdown of OsDCL1, which is targeted by osa-miR162a, inhibited α-linolenic acid metabolism to enhance the resistance to the BPH, which was similar to that in miR162a-overexpressing plants. Our study revealed a novel defense mechanism mediated by plant miRNAs developed during the long-term evolution of plant-host interaction, provided new ideas for the identification of rice resistance resources, and promoted a better understanding of pest control.

Utilization of nitrogen, sulfur co-doped porous carbon micron spheres as bifunctional electrocatalysts for electrochemical detection of cadmium, lead and mercury ions and oxygen evolution reaction.

The development of high-performance bifunctional electrocatalysts for oxygen evolution reaction and heavy metal ion (HMI) detection is significant and challenging. Here, a novel nitrogen, sulfur co-doped porous carbon sphere bifunctional catalyst was designed and fabricated by hydrothermal followed by carbonization using starch as carbon source and thiourea as nitrogen, sulfur source for HMI detection and oxygen evolution reactions. Under the synergistic effect of pore structure, active sites and nitrogen, sulfur functional groups, C-S0.75-HT-C800 demonstrated excellent HMI detection performance and oxygen evolution reaction activity. Under optimized conditions, the detection limits (LODs) of C-S0.75-HT-C800 sensor were 3.90, 3.86 and 4.91 nM for Cd2+, Pb2+ and Hg2+ when detected individually; and the sensitivities were 13.12, 19.50 and 21.19 µA/µM. The sensor also obtained high recoveries of Cd2+, Hg2+ and Pb2+ in river water samples. During the oxygen evolution reaction, a Tafel slope of 70.1 mV/dec and a low overpotential of 277 mV were obtained for C-S0.75-HT-C800 electrocatalyst with a current density of 10 mA/cm2 in basic electrolyte. This research offers a neoteric and simple strategy in the design as well as fabrication of bifunctional carbon-based electrocatalysts.

Evolution of the Composition and Melting Behavior of Spinnable Pitch during Incubation.

The physical and chemical properties of spinnable pitch showed a huge impact on the performance of resultant pitch carbon fiber even if its physical and chemical properties were slightly changed. Various polycyclic aromatic compounds and abundant free radicals existed in spinnable pitch, and there are many interactions among molecules and free radicals. The molecular structure and composition of spinnable pitch were investigated during incubation, and the effect of molecular evaluation on rheological properties of spinnable pitch was illustrated using various characterization methods in this work. It indicated that n-hexane soluble fraction mainly occurred condensation or cleavage, and a small number of heavy components were generated after a long period. The fraction of n-hexane insoluble/toluene soluble underwent molecular condensation and cross-linking in the presence of oxygen-containing radicals and aromatic hydrocarbon radicals, while toluene insoluble/tetrahydrofuran soluble fraction tended to change in large molecules of polycyclic aromatic hydrocarbons. Lastly, tetrahydrofuran insoluble fraction was condensed due to its high aromaticity during the incubation process, and the content of aromatic carbon increased. These changes of composition and structure of spinnable pitch led to its softening point, increase in viscosity and flow activation energy, and deterioration of the rheological property.

One-step synthesis of SiO2 nanomesh for antireflection and self-cleaning of solar cell.

SiO2 nanomaterials are widely used for antireflection and self-cleaning, but the preparation process is usually complex and time-consuming. Hence, we present a facile one-step synthesis of a hydrophobic two-dimensional SiO2 nanomesh by tuning the reaction temperature using dodecylamine as a catalyst. SiO2 nanomesh has the advantages of an adjustable refractive index, simple preparation process, and low cost, which affords both antireflection and self-cleaning functions for solar cells. Two types of perovskite solar cells were used to verify the stability and universality of the SiO2 nanomesh coatings. The antireflection effect of the SiO2 nanomesh is found to increase the current density of both perovskite solar cells fabricated at 500 °C and 150 °C, with the efficiency increased by 4.48% and 4.79%, respectively.

Plasma membrane-nucleo-cytoplasmic coordination of a receptor-like cytoplasmic kinase promotes EDS1-dependent plant immunity.

Plants use cell-surface immune receptors to recognize pathogen-specific patterns to evoke basal immunity. ENHANCED DISEASE SUSCEPTIBILITY (EDS1) is known to be crucial for plant basal immunity, whereas its activation mechanism by pattern recognition remains enigmatic. Here, we show that the fungal pattern chitin induced the plasma membrane-anchored receptor-like cytoplasmic kinase PBS1-LIKE 19 (PBL19) to undergo nuclear translocation in Arabidopsis. The palmitoylation-deficient PBL19C3A variant constantly resided in the nucleus, triggering transcriptional self-amplification mainly through WRKY8 and EDS1-dependent constitutive immunity. Unexpectedly, the metacaspase-cleaved PBL19 lacking the N-terminal nuclear localization sequence specifically interacted with and phosphorylated EDS1 in the cytoplasm. Phosphodeficient EDS1 attenuated PBL19C3A-induced constitutive immunity, while phosphomimetic EDS1 complemented the loss of PBL19 for fungal resistance. Collectively, these findings reveal a compelling model wherein the plasma membrane, nuclear and cytoplasmic pools of PBL19 temporally coordinate distinct roles of immune signal receiver, amplifier and effector to boost plant antifungal immunity via EDS1.

Broadband and photovoltaic THz/IR response in the GaAs-based ratchet photodetector.

High-performance broadband infrared (IR)/terahertz (THz) detection is crucial in many optoelectronic applications. However, the spectral response range of semiconductor-based photodetectors is limited by the bandgaps. This paper proposes a ratchet structure based on the GaAs/AlxGa1-xAs heterojunction, where the quasi-stationary hot hole distribution and intravalence band absorption from light or heavy hole states to the split-off band overcome the bandgap limit, ensuring an ultrabroadband photoresponse from near-IR to THz region (4 to 300 THz). The peak responsivity of the proposed structure can reach 7.3 A/W, which is five orders of magnitude higher than that of the existing broadband photon-type detector. Because of the ratchet effect, the proposed photodetector has a bias-tunable photoresponse characteristic and can operate in the photovoltaic mode with a broad photocurrent spectrum (18 to 300 THz). This work not only demonstrates a broadband photon-type THz/IR photodetector but also provides a method to study the light-responsive ratchet.

Hierarchically nanostructured Zn0.76C0.24S@Co(OH)2 for high-performance hybrid supercapacitor.

It is a great challenge to achieve both high specific capacity and high energy density of supercapacitors by designing and constructing hybrid electrode materials through a simple but effective process. In this paper, we proposed a hierarchically nanostructured hybrid material combining Zn0.76Co0.24S (ZCS) nanoparticles and Co(OH)2 (CH) nanosheets using a two-step hydrothermal synthesis strategy. Synergistic effects between ZCS nanoparticles and CH nanosheets result in efficient ion transports during the charge-discharge process, thus achieving a good electrochemical performance of the supercapacitor. The synthesized ZCS@CH hybrid exhibits a high specific capacity of 1152.0 C g-1 at a current density of 0.5 A g-1 in 2 M KOH electrolyte. Its capacity retention rate is maintained at âˆ¼ 70.0% when the current density is changed from 1 A g-1 to 10 A g-1. A hybrid supercapacitor (HSC) assembled from ZCS@CH as the cathode and active carbon (AC) as the anode displays a capacitance of 155.7 F g-1 at 0.5 A g-1, with a remarkable cycling stability of 91.3% after 12,000cycles. Meanwhile, this HSC shows a high energy density of 62.5 Wh kg-1 at a power density of 425.0 W kg-1, proving that the developed ZCS@CH is a promising electrode material for energy storage applications.

Plant elicitor peptide signalling confers rice resistance to piercing-sucking insect herbivores and pathogens.

Rice is a staple food crop worldwide, and its production is severely threatened by phloem-feeding insect herbivores, particularly the brown planthopper (BPH, Nilaparvata lugens), and destructive pathogens. Despite the identification of many BPH resistance genes, the molecular basis of rice resistance to BPH remains largely unclear. Here, we report that the plant elicitor peptide (Pep) signalling confers rice resistance to BPH. Both rice PEP RECEPTORs (PEPRs) and PRECURSORs of PEP (PROPEPs), particularly OsPROPEP3, were transcriptionally induced in leaf sheaths upon BPH infestation. Knockout of OsPEPRs impaired rice resistance to BPH, whereas exogenous application of OsPep3 improved the resistance. Hormone measurement and co-profiling of transcriptomics and metabolomics in OsPep3-treated rice leaf sheaths suggested potential contributions of jasmonic acid biosynthesis, lipid metabolism and phenylpropanoid metabolism to OsPep3-induced rice immunity. Moreover, OsPep3 elicitation also strengthened rice resistance to the fungal pathogen Magnaporthe oryzae and bacterial pathogen Xanthamonas oryzae pv. oryzae and provoked immune responses in wheat. Collectively, this work demonstrates a previously unappreciated importance of the Pep signalling in plants for combating piercing-sucking insect herbivores and promises exogenous application of OsPep3 as an eco-friendly immune stimulator in agriculture for crop protection against a broad spectrum of insect pests and pathogens.

MnCo2O4/Ni3S4 nanocomposite for hybrid supercapacitor with superior energy density and long-term cycling stability.

MnCo2O4 is regarded as a good electrode material for supercapacitor due to its high specific capacity and good structural stability. However, its poor electrical conductivity limits its wide-range applications. To solve this issue, we integrated the MnCo2O4 with Ni3S4, which has a good electrical conductivity, and synthesized a MnCo2O4/Ni3S4 nanocomposite using a two-step hydrothermal process. Comparing with individual MnCo2O4 and Ni3S4, the MnCo2O4/Ni3S4 nanocomposite showed a higher specific capacity and a better cycling stability as the electrode for the supercapacitor. The specific capacity value of the MnCo2O4/Ni3S4 electrode was 904.7 C g-1 at 1 A g-1 with a potential window of 0-0.55 V. A hybrid supercapacitor (HSC), assembled using MnCo2O4/Ni3S4 and active carbon as the cathode and anode, respectively, showed a capacitance of 116.4 F g-1 at 1 A g-1, and a high energy density of 50.7 Wh kg-1 at 405.8 W kg-1. Long-term electrochemical stability tests showed an obvious increase of the HSC's capacitance after 5500 charge/discharge cycles, reached a maximum value of ∼162.7% of its initial value after 25,000 cycles, and then remained a stable value up to 64,000 cycles. Simultaneously, its energy density was increased to 54.2 Wh kg-1 at 380.3 W kg-1 after 64,000 cycles.

Overexpression of an Osa-miR162a Derivative in Rice Confers Cross-Kingdom RNA Interference-Mediated Brown Planthopper Resistance without Perturbing Host Development.

Rice is a main food crop for more than half of the global population. The brown planthopper (BPH, Nilaparvata lugens) is one of the most destructive insect pests of rice. Currently, repeated overuse of chemical insecticides represents a common practice in agriculture for BPH control, which can induce insect tolerance and provoke environmental concerns. This situation calls for innovative and widely applicable strategies for rice protection against BPH. Here we report that the rice osa-miR162a can mediate cross-kingdom RNA interference (RNAi) by targeting the NlTOR (Target of rapamycin) gene of BPH that regulates the reproduction process. Through artificial diet or injection, osa-miR162a mimics repressed the NlTOR expression and impaired the oviposition of BPH adults. Consistently, overproduced osa-miR162a in transgenic rice plants compromised the fecundity of BPH adults fed with these plants, but meanwhile perturbed root and grain development. To circumvent this issue, we generated osa-miR162a-m1, a sequence-optimized osa-miR162a, by decreasing base complementarity to rice endogenous target genes while increasing base complementarity to NlTOR. Transgenic overexpression of osa-miR162a-m1 conferred rice resistance to BPH without detectable developmental penalty. This work reveals the first cross-kingdom RNAi mechanism in rice-BPH interactions and inspires a potentially useful approach for improving rice resistance to BPH. We also introduce an effective strategy to uncouple unwanted host developmental perturbation from desirable cross-kingdom RNAi benefits for overexpressed plant miRNAs.

Enhancement in external quantum efficiency of light-emitting diode based on colloidal silicon nanocrystals.

Herein, we report an enhanced red emission from colloidal silicon nanocrystals (c-Si NCs) solution-processed light-emitting diode. c-Si NCs were synthesized by facile femtosecond laser ablation. Based on the structural characterization and opto-electrics properties analysis, both photoluminescence and electroluminescence arise from the radiative recombination of carriers due to quantum confined effect. The optical power density and highest external quantum efficiency have been obtained to be 0.79 mW cm-2and âˆ¼6.6%, respectively. These results indicate that Si NCs are very attractive as a potential optical source for future integrated chips.

Interfacial and Permeating Modification Effect of n-type Non-fullerene Acceptors toward High-Performance Perovskite Solar Cells.

Interface passivation in the electron transport layer (ETL) has emerged as a very important and challenging topic for the improvement of stability and efficiency of perovskite solar cells (PSCs). Here, we introduce the n-type small organic molecule Y6 that acts as an effective ETL modifier through surface engineering. As a result, the simple PCBM + Y6 ETL led to significantly stronger light absorption, higher electron extraction ability and transportability, and reduced recombination loss in regular MAPbI3 PSCs. The power conversion efficiency can be significantly increased from 17.39 to 20.02% in inverted p-i-n MAPbI3 PSCs without additional alternation, with an increment of over 15%, along with higher open-circuit voltage and short-circuit current. What is more, the devices with the Y6-modified ETL also exhibited better long-term stability compared to the control devices. This indicates the feasibility of enhancing absorption over a wider light spectrum in a single-junction cell and gaining a comprehensive understanding of interface engineering between the ETL and perovskite layer.

Flexible all-solid-state supercapacitors based on PPy/rGO nanocomposite on cotton fabric.

Polypyrrole (PPy) has high electrochemical activity and low cost, so it has great application prospects in wearable supercapacitors. Herein, we have successfully prepared polypyrrole/reduced graphene oxide (PPy/rGO) nanocomposite cotton fabric (NCF) by chemical polymerization, which exhibits splendid electrochemical performance compared with the individual. The addition of rGO can block the deformation of PPy caused by the expansion and contraction. The as-prepared PPy-0.5/rGO NCF electrode exhibits the brilliant specific capacitance (9300 mF cm-2at 1 mA cm-2) and the capacitance retention with 94.47% after 10 000 cycles. At the same time, the superior capacitance stability under different bending conditions and reuse capability have been achieved. All-solid-state supercapacitor has high energy density of 167µWh cm-2with a power density of 1.20 mW cm-2. Therefore, the PPy-0.5/rGO NCF electrode has a broad application prospect in high-performance flexible supercapacitor fabric electrode.

SnO x /graphene anode material with multiple oxidation states for high-performance Li-ion batteries.

Tin and its oxides are promising anode materials owing to their high theoretical capacity, rich resource, and environmental benignity. To achieve low cost and green synthesis, a facile synthetic route of SnO x /graphene composites is proposed, using a simple galvanic replacement method to quickly obtain abundant foamed tin as raw material and ball milling method to realize a mechanochemical reaction between SnO x (0 ≤ x ≤ 2) and graphene. Under different annealing conditions, the foamed tin is converted to tin oxides with multiple oxidation states (Sn3O4, SnO, and SnO2). These unique components can greatly affect the electrochemical performance of the electrode in LIBs. The as-prepared electrode (SnO x -300/G) obtained by annealing foamed tin at 300 °C for 4 h and combining SnO x powders with graphene via ball milling shows great cycling stability, retaining a high capacity of 786 mA h g-1 at 0.1 A g-1 after 150 cycles, and its initial Coulombic efficiency can reach 84.03%. Thus, this facile synthesis can provide an environmentally friendly route for commercial production of high-performance energy storage materials.

Porous 3D graphene aerogel co-doped with nitrogen and sulfur for high-performance supercapacitors.

Heteroatom-doped carbon materials with a high specific area, a well-defined porous structure is important to high-performance supercapacitors (SCs). Here, S and N co-doped three-dimensional porous graphene aerogel (NS-3DPGHs) have been synthesized in a facile and efficient self-assembly process with thiourea acting as the reducing and doping agent solution. Operating as a SC electrode, fabricated co-doping graphene, i.e. the sample of NS-3DPGH-150 exhibits the highest specific capacitance of 412.9 F g-1 under 0.5 A g-1 and prominent cycle stabilization with 96.4% capacitance retention in the back of 10 000 cycles. Furthermore, based on NS-3DPGH-150, the symmetrical supercapacitor as-prepared in 6 M KOH displays a superior energy density of 12.9 Wh kg-1 under the power density of 249 W kg-1. Hence, NS-3DPGHs could be considered as an excellent candidate for SCs.

Electrochemical Deposition of CsPbBr3 Perovskite for Photovoltaic Devices with Robust Ambient Stability.

Alkali halide perovskites have emerged as representative candidates for novel opto-electronic devices owing to their balanced efficiency and stability. However, their fabrication method still remains a challenging topic with conflicts among their effectiveness, complexity, and cost. Herein, a complete two-step electrochemical method has been applied in the fabrication of inorganic perovskites for the first time. The dimension and microstructure of CsPbBr3 can be easily controlled by variation of simple physical parameters during the fabrication. By optimizing the parameters, high-quality CsPbBr3 films are obtained, and the champion device has achieved an efficiency of 7.86% with a high open-circuit voltage of 1.43 V. More importantly, the as-fabricated materials have shown an extraordinary robust stability against environmental conditions even after 150 days of exposure to air without encapsulation. This has evidently proved the electrochemical methods as an effective route for perovskite synthesis in its future development.

High-Efficiency Silicon Inverted Pyramid-Based Passivated Emitter and Rear Cells.

Surface texturing is one of the most important techniques for improving the performance of photovoltaic (PV) device. As an appealing front texture, inverted pyramid (IP) has attracted lots of research interests due to its superior antireflection effect and structural characteristics. In this paper, we prepare high-uniform silicon (Si) IPs structures on a commercial monocrystalline silicon wafer with a standard size of 156 × 156 mm2 employing the metal-assisted chemical etching (MACE) and alkali anisotropic etching technique. Combining the front IPs textures with the rear surface passivation of Al2O3/SiNx, we fabricate a novel Si IP-based passivated emitter and rear cell (PERC). Benefiting from the optical superiority of the optimized IPs and the improvement of electrical performance of the device, we achieve a high efficiency of 21.4% of the Si IP-based PERC, which is comparable with the average efficiency of the commercial PERC solar cells. The optimizing morphology of IP textures is the key to the improvement of the short circuit current Isc from 9.51 A to 9.63 A; meanwhile, simultaneous stack SiO2/SiNx passivation for the Si IP-based n+ emitter and stack Al2O3/SiNx passivation for rear surface guarantees a high open-circuit voltage Voc of 0.677 V. The achievement of this high-performance PV device demonstrates a competitive texturing technique and a promising prospect for the mass production of the Si IP-based PERC.