Abstract 2D Ruddlesden–Popper perovskites (RPPs) have recently drawn significant attention because of their structural variability that can be used to tailor optoelectronic properties and improve the stability of derived photovoltaic devices. However, charge separation and transport in 2D perovskite solar cells (PSCs) suffer from quantum well barriers formed during the processing of perovskites. It is extremely difficult to manage phase distributions in 2D perovskites made from the stoichiometric mixtures of precursor solutions. Herein, a generally applicable guideline is demonstrated for precisely controlling phase purity and arrangement in RPP films. By visually presenting the critical colloidal formation of the single‐crystal precursor solution, coordination engineering is conducted with a rationally selected cosolvent to tune the colloidal properties. In nonpolar cosolvent media, the derived colloidal template enables RPP crystals to preferentially grow along the vertically ordered alignment with a narrow phase variation around a target value, resulting in efficient charge transport and extraction. As a result, a record‐high power conversion efficiency (PCE) of 14.68% is demonstrated for a (TEA) 2 (MA) 2 Pb 3 I 10 ( n = 3) photovoltaic device with negligible hysteresis. Remarkably, superior stability is achieved with 93% retainment of the initial efficiency after 500 h of unencapsulated operation in ambient air conditions.
In the study of rock mechanics, the variation of rock mechanical characteristics in high-temperature environments is always a major issue. The discrete element method and Voronoi modeling method were used to study the mechanical characteristics and crack evolution of granite specimens subjected to the high temperature and uniaxial compression test in order to study the internal crack evolution process of granite under the influence of high temperatures. Meanwhile, dependable findings were acquired when compared to experimental outcomes. A modified failure criterion was devised, and a Fish function was built to examine the evolution behavior of tensile and shear cracks during uniaxial compression, in order to better understand the evolution process of micro-cracks in granite specimens. Shear contacts occurred first, and the number of shear cracks reached its maximum value earliest, according to the findings. The number of tensile contacts then rapidly grew, whereas the number of shear cracks steadily declined. Furthermore, it was found that when temperature rises, the number of early tensile cracks grows. This study develops a fracture prediction system for rock engineering in high-temperature conditions.
In this paper, a new mode of deep perforated sub-wavelength metallic hole arrays in hexagonal lattice is presented. The transmission spectrum is obtained with Finite-difference time-domain (FDTD) and measured with Fourier infrared spectrometer. In the resonance peak scope, the Electric-field intensity is similar to 80 times larger than that of the incident wave at near field. The resonance of this structure can enhance the near-field intensity and improve the absorption efficiency of photodetector.
Al2O3 ceramic and 1A95 aluminum alloy vacuum brazed joints were prepared with Al-Si-Mg-La solder. The effects of brazing temperature on the structure and shear properties of brazed joints were studied, and the interface of the joints was analyzed. Studies have shown that the shear strength of Al2O3/Ag-Si-Mg-La/Al joints all show a trend of increasing first and then decreasing with the increase of brazing temperature and holding time; when the best brazing process is 590°C×20 min, the boundary between Al-Si-Mg-La solder and aluminum alloy disappears; the interface between Al2O3 ceramic and solder is well bonded, and the shear strength is 56.74MPa. The fracture form of the joint is brittle fracture. Under different brazing process parameters, the fracture position of the joint is mainly divided into two types: when the joint strength is low, the fracture occurs near the interface between the aluminum alloy and the brazing filler metal layer; when the joint strength is higher, the fracture occurs at the interface between the Al2O3 ceramic and the solder.
The road transport sector in megacities is confronted with pressing local air pollution and carbon dioxide (CO2) control issues. To determine effective policy instruments for saving energy and the co-control of air pollutants and CO2, several mainstream measures were examined and compared in Chongqing's road transport sector from 2017 to 2035. An integration assessment framework was developed by combining the Long-range Energy Alternatives Planning (LEAP) system and a set of quantitative methods for evaluating the co-benefits of emission reductions (including the air pollutant equivalent (APeq), co-control coordinate system, and pollutant reduction cross-elasticity (Elsa/b)). Results showed that the shifting transportation modes scenario presented the most significant potential for energy-saving and emission reductions, reducing energy use by 30.9% and air pollutants and CO2 emissions by approximately 27-32% compared with the business as usual (BAU) scenario in 2035. The improving energy efficiency scenario also provided significant co-benefits for reducing air pollutants and CO2 emissions. Nevertheless, the promoting alternative fuel scenario may increase fine particulate matter (PM2.5) emissions by 2.2% compared to BAU in 2035 under the cleanness of regional electricity in 2017. Our findings suggest that the shifting transportation modes were effective measures to reduce air pollutants and CO2 in the short term synergistically, and highlighted the importance of cleaner electricity generation to develop electric vehicles in the medium and long term.
Sn-Bi solder alloys have been widely used in electronic devices due to its low melting point, low thermal expansion coefficient and good mechanical properties. However, due to the brittleness of Bi element in SnBi solder, Bi phase is easy to be vulgar at high temperature, which leads to poor plasticity and ductility of solder joint, which affects the reliability of solder joint in high temperature service. The results show that the wettability, tensile strength and ductility of Sn58Bi solder can be improved when the content of Er is 0.1%. In this paper, Sn58Bi-0.1Er was used as the base metal, and the effects of Ni-CNTs particle reinforced phase on the melting characteristics, mechanical properties, microstructure and composition of the solder were discussed. The results of XRD shows that with the addition of Ni-CNTs, Ni element reacts with Sn to form Ni3Sn4 intermetallic compound, while carbon nanotubes still exist in the form of carbon element. The increase of Ni-CNTs particles can reduce the dendrite structure and refine the microstructure of the composite solder. The addition of Ni-CNTs increased the melting temperature of the composite solder. The tensile test results shows that with the increase of Ni-CNTs particles, the tensile strength and elongation of the composite solder increase first and then decrease. When the content of Ni-CNTs particles is 0.03%, the elongation of composite solder is 82.06%, which is 43% higher than that of Sn58Bi-0.1Er.
Seismic fragility analysis is an efficient way to study the seismic behaviour and performance of structures under the excitation of earthquakes of varying intensity, and an essential part of the seismic risk assessment of structures. A recently developed dynamic reliability methodology, the probability density evolution method (PDEM), is proposed for the dynamic reliability and seismic fragility analysis of a retaining wall. The PDEM can obtain an instantaneous probability density function of the seismic responses and easily acquire the seismic reliability of the structural system. An important advantage of the PDEM is its high efficiency relative to that of the Monte Carlo simulation method, which is often used in the reliability and fragility analysis of structures. The present study uses a typical gravity retaining wall to illustrate stochastic seismic responses and fragility curves that can be obtained by the PDEM. The combined uncertainties of the seismic force and soil properties are explicitly and systematically modelled by stochastic ground motions and random variables respectively. The performance of the retaining wall is analysed for different acceptable levels of backfill settlement. Additionally, seismic fragility curves are constructed without assuming the distribution of the seismic response.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)