Nitrogen fertilisation management in precision agriculture: a preliminary application example on maize

The adoption of precision agriculture techniques for N management has the potential for improving agronomic, economic and environmental efficiency in the use of such input. The present work was aimed at testing a simplified N balance method for the prescription of N fertilisation in uniform management zones defined from information on measured soil properties on grain maize in central Italy. The results of this preliminary experience show that the application of the N balance prescription map did not bring to significant differences, from a uniform N fertilisation, in terms of grain yield, economic return above N cost and nitrate content in the soil profile at the end of the growing season. However, the adoption of the prescribed N fertilisation strategy for the whole field would have caused a limited saving in the amount of fertiliser employed, quantified at about 10 kg N ha–1

Hydrophobic 4-(isopropylbenzyl)oxy-substituted metallophthalocyanines as a dopant-free hole selective material for high-performance and moisture-stable perovskite solar cells

WOS:001009990300001Dopant-free hole-transporting materials (HTMs) are necessary to overcome the instability for perovskite solar cells (PSCs) originating from conventional HTMs such as spiro-OMeTAD requiring hygroscopic dopants for future commercialization. Herein, a series of dopant-free HTMs based on peripherally 4-(isopropylbenzyl)oxy-substituted phthalocyanines with different core metals (EG-pZn1, EG-pCu1, and EG-pNi1) are designed and introduced as a hole-transport layer in PSCs for the first time. The introduction of hydrophobic bulky 4-(isopropylbenzyl)oxy moieties to the phthalocyanine structure favors excellent moisture-resistant effect, and good solubility, as well as suppression of charge recombination in PSCs. Three HTMs-based cells afford an impressive efficiency of 17.60% (EG-pNi1), 16.45% (EG-pCu1), and 15.83% (EG-pZn1) with the character of hysteresis-free. More importantly, while EG-pNi1 and EG-pCu1 HTL-based devices can effectively protect perovskite film from moisture which degraded to only 10% of its initial efficiency under humidity level (60–65%) after a period of 20 days, unexpectedly, ∼30% loss of initial efficiency has been observed in EG-pZn1 HTM based devices under the same conditions. Furthermore, EG-pNi1-based devices also show excellent thermal stability, maintaining 95% initial efficiency after aging for 20 days at 85 °C. These results demonstrate the role of peripherally substituted hydrophobic 4-(isopropylbenzyl)oxy group in HTMs on photovoltaic performance and moisture-/thermal-stability of PSCs and its potential in reasonable and effective ways of industrial commercialization of PSCs

Core–Shell Nanocomposites for Improving the Structural Stability of Li-Rich Layered Oxide Cathode Materials for Li-Ion Batteries

The structural stability of Li-rich layered oxide cathode materials is the ultimate frontier to allow the full development of these family of electrode materials. Here, first-principles calculations coupled with cluster expansion are presented to investigate the electrochemical activity of phase-separation, core–shell-structured <i>x</i>Li₂MnO₃·(1 – <i>x</i>)­LiNiCoMnO₂ nanocomposites. The detrimental surface effects of the core region can be countered by the Li₂MnO₃ shell, which stabilizes the nanocomposites. The operational voltage windows are accurately determined to avoid the electrochemical activation of the shell and the subsequent structural evolution. In particular, the dependence of the activation voltage with the shell thickness shows that relatively high voltages can still be obtained to meet the energy density needs of Li-ion battery applications. Finally, activation energies of Li migration at the core–shell interface must also be analyzed carefully to avoid the outbreak of a phase transformation, thus making the nanocomposites suitable from a structural viewpoint

Surface-energy engineered Bi-doped SnTe nanoribbons with weak antilocalization effect and linear magnetoresistance

The rational design of semiconductor nanocrystals with well-defined surfaces is a crucial step towards the realization of next-generation photodetectors, and thermoelectric and spintronic devices. SnTe nanocrystals, as an example, are particularly attractive as a type of topological crystalline insulator, where surface facets determine their surface states. However, most of the available SnTe nanocrystals are dominated by thermodynamically stable {100} facets, and it is challenging to grow uniform nanocrystals with {111} facets. In this study, guided by surface-energy calculations, we employ a chemical vapour deposition approach to fabricate Bi doped SnTe nanostructures, in which their surface facets are tuned by Bi doping. The obtained Bi doped SnTe nanoribbons with distinct {111} surfaces show a weak antilocalization effect and linear magnetoresistance under high magnetic fields, which demonstrate their great potential for future spintronic applications

Improving the performance of arylamine-based hole transporting materials in perovskite solar cells: Extending pi-conjugation length or increasing the number of side groups?

In this work, we prepared three simple arylamine-based hole transporting materials from commercially available starting materials. The effect of extending π-conjugation length or increasing the number of side groups compared with reference compound on the photophysical, electrochemical, hole mobility properties and performance in perovskite solar cells were further studied. It is noted that these two kinds of molecular modifications can significantly lower the HOMO level and improve the hole mobility, thus improving the hole injection from valence band of perovskite. On the other hand, the compound with more side groups showed higher hole injection efficiency due to lower HOMO level and higher hole mobility compared with the compound with extending π-conjugation length. The perovskite solar cells with the modified molecules as hole transporting materials showed a higher efficiency of 15.40% and 16.95%, respectively, which is better than that of the reference compound (13.18%). Moreover, the compound with increasing number of side groups based devices showed comparable photovoltaic performance with that of conventional spiro-OMeTAD (16.87%)

Molecular engineering of simple benzene–arylamine hole-transporting materials for perovskite solar cells

Three benzene–arylamine hole-transporting materials (HTMs) with different numbers of terminal groups were prepared. It is noted that the molecule with three arms (H-Tri) shows a lower highest occupied molecular orbital level and a better film morphology on perovskite layer than the molecules with two or four arms (H-Di, H-Tetra). When these molecules were applied to the perovskite solar cells, the H-Tri-based one showed better performance compared with the H-Di- or H-Tetra-based ones. Photoluminescence and impedance spectroscopy demonstrate that H-Tri can improve the hole–electron separation efficiency and decrease the charge recombination, thus leading to a better performance. Moreover, the H-Tri-based device shows a comparable performance and a much less materials cost than the conventional spiro-OMeTAD. Therefore, we have presented a new low-cost and high-performance HTM through simple molecular engineering

Atomic Insights into Phase Evolution in Ternary Transition-Metal Dichalcogenides Nanostructures

Phase engineering through chemical modification can significantly alter the properties of transition-metal dichalcogenides, and allow the design of many novel electronic, photonic, and optoelectronics devices. The atomic-scale mechanism underlying such phase engineering is still intensively investigated but elusive. Here, advanced electron microscopy, combined with density functional theory calculations, is used to understand the phase evolution (hexagonal 2H -> monoclinic T'-> orthorhombic T-d) in chemical vapor deposition grown Mo1-xWxTe2 nanostructures. Atomic-resolution imaging and electron diffraction indicate that Mo1-xWxTe2 nanostructures have two phases: the pure monoclinic phase in low W-concentrated (0 Td with low energy state. This work enriches the atomic-scale understanding of phase evolution and coexistence in multinary compounds, and paves the way for device applications of new transition-metal dichalcogenides phases and heterostructures

Atomic disorders in layer structured topological insulator SnBi2Te4 nanoplates

Identification of atomic disorders and their subsequent control has proven to be a key issue in predicting, understanding, and enhancing the properties of newly emerging topological insulator materials. Here, we demonstrate direct evidence of the cation antisites in single-crystal SnBi2Te4 nanoplates grown by chemical vapor deposition, through a combination of sub-angstrom-resolution imaging, quantitative image simulations, and density functional theory calculations. The results of these combined techniques revealed a recognizable amount of cation antisites between Bi and Sn, and energetic calculations revealed that such cation antisites have a low formation energy. The impact of the cation antisites was also investigated by electronic structure calculations together with transport measurement. The topological surface properties of the nanoplates were further probed by angle-dependent magnetotransport, and from the results, we observed a two-dimensional weak antilocalization effect associated with surface carriers. Our approach provides a pathway to identify the antisite defects in ternary chalcogenides and the application potential of SnBi2Te4 nanostructures in next-generation electronic and spintronic devices

Ab Initio Study on Surface Segregation and Anisotropy of Ni-Rich LiNi_{1–2<i>y</i>}Co_<i>y</i>Mn_<i>y</i>O₂ (NCM) (<i>y</i> ≤ 0.1) Cathodes

Advances in ex situ and in situ (operando) characteristic techniques have unraveled unprecedented atomic details in the electrochemical reaction of Li-ion batteries. To bridge the gap between emerging evidences and practical material development, an elaborate understanding on the electrochemical properties of cathode materials on the atomic scale is urgently needed. In this work, we perform comprehensive first-principle calculations within the density functional theory + <i>U</i> framework on the surface stability, morphology, and elastic anisotropy of Ni-rich LiNi_{1–2<i>y</i>}Co_<i>y</i>Mn_<i>y</i>O₂ (NCM) (<i>y</i> ≤ 0.1) cathode materials, which are strongly related to the emerging evidence in the degradation of Li-ion batteries. On the basis of the surface stability results, the equilibrium particle morphology is obtained, which is mainly determined by the oxygen chemical potential. Ni-rich NCM particles are terminated mostly by the (012) and (001) surfaces for oxygen-poor conditions, whereas the termination corresponds to the (104) and (001) surfaces for oxygen-rich conditions. Besides, Ni surface segregation predominantly occurs on the (100), (110), and (104) nonpolar surfaces, showing a tendency to form a rocksalt NiO domain on the surface because of severe Li–Ni exchange. The observed elastic anisotropy reveals that an uneven deformation is more likely to be formed in the particles synthesized under poor-oxygen conditions, leading to crack generation and propagation. Our findings provide a deep understanding of the surface properties and degradation of Ni-rich NCM particles, thereby proposing possible solution mechanisms to the factors affecting degradation, such as synthesis conditions, coating, or novel nanostructures

A Simple Carbazole-Triphenylamine Hole Transport Material for Perovskite Solar Cells

In this work, a simple carbazole-based hole transport material with triphenylamine moieties, termed LD22, has been used in perovskite solar cells (PSCs). It is noted that LD22 exhibits a proper HOMO level of -5.27 eV, high hole mobility of 1.65 X 10(-5) cm(2) V-1 s(-1), and relatively high glass-transition temperature of 132 degrees C. When LD22 was used in PSCs, pristine LD22-based PSCs showed a power conversion efficiency (PCE) of 13.04%. When LD22 is doped, the PCE improves to a promising 17.18%. More importantly, the concentration of LD22 has little influence on the PSC performance regardless of the existence of dopants, which shows good repeatability. As a reference, the device with doped 2,2',7,7'-tetrakis(N,N-bis(4-methoxyphenyl)amino)-9,9'-spiro-bifluorene (spiro-OMeTAD) shows a PCE of 17.73%. On the other hand, the laboratory synthesis cost of LD22 is much lower than that of spiro-OMeTAD. Therefore, the results indicate that the simple carbazole-triphenylamine compounds own the potential to be doped-free HTM and LD22 could be a promising HTM candidate for high-performance PSCs due to its simple structure