Influence of the Nature of A Cation on Dynamics of Charge Transfer Processes in Perovskite Solar Cells

The electronic processes occurring within the perovskite solar cells (PSCs) are strongly influenced by the nature of the organic A cations present within the inorganic framework. In this study, the impact of FA (CH(NH₂)₂⁺) and Cs⁺ cations on the intrinsic and interfacial properties in the FAPbBr₃ and CsPbBr₃ PSCs is investigated. The analysis of current density ( J _SC) and photovoltage ( V _OC) as a function of illumination intensity establishes that the interfacial charge transport is more rapid in FAPbBr₃ devices. Small perturbation measurements including intensity modulated photocurrent and photovoltage spectroscopy are applied to explore the resistive and capacitive elements. Furthermore, electrochemical impedance spectroscopy measurements are found to correlate well with the photovoltaic characteristics of FAPbBr₃ and CsPbBr₃ PSCs. Overall, the in‐depth analysis of various phenomena occurring within the bromide PSCs allows to underline the working principle, which provides a key to optimize the device performance. The present protocol is not only valid for PSCs but can also be extended to devices based on alternative light harvesters.     

Subsurface plastic deformation in machining annealed red brass

The effect of cutting speed and tool geometry on the plastic deformation in the surface region of annealed red brass machined orthogonally under lubricated and unlubricated conditions is determined using the grid technique and metallography.The results show that the magnitude of the plastic deformation in the surface region and the depth of the work-hardened layer increase with a decrease in the cutting speed or the tool rake angle. Change in the tool wear land length produces a lesser change in the subsurface deformation than that observed to be due to a change in the other cutting parameters.The presence of the lubricant in the cutting region results in a considerable reduction in the subsurface damage.     

Heterogeneous Load Balancing using Predictive Load Summarization

Wireless Personal Communications - Enhanced throughput under efficient dynamic spectrum access is possible by secondary access based cognitive radio networking in TV white space (TVWS). The current...     

An Efficient Cross Layer Design of Stability Based Clustering Scheme Using Ant Colony Optimization in VANETs

Wireless Personal Communications - Road Accident is a significant concern in every county. According to WHO (World Health Organization) reports, 1.3 million people died in road traffic crashes, and...     

Correction to: Heterogeneous Load Balancing using Predictive Load Summarization

Wireless Personal Communications -     

Dopant Engineering for Spiro-OMeTAD Hole-Transporting Materials towards Efficient Perovskite Solar Cells

One of the most prominent hole-transporting material (HTM) for hybrid perovskite solar cells has been 2,2″,7,7″-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD), which is commonly doped with metal bis(trifluoromethylsulfonyl)imide (M(TFSI)_n) salts that contribute to generating the active radical cation HTM species. The underlying role of the metal cation, however, remains elusive. Here, the effect of metal cations (M = Li, Zn, Ca, Cu, and Sc) on doping spiro-OMeTAD is analyzed by a combination of techniques, including electron paramagnetic resonance spectroscopy and cyclic voltammetry, which is complemented by photovoltaic device and hole mobility analysis. As a result, the authors reveal the superiority of Zn(TFSI)₂ salts in device performances as compared to the others, including redox-active Cu(TFSI)₂. This analysis thereby unravels new design principles for dopant engineering in HTMs for hybrid perovskite photovoltaics.     

Fundamentals of Materials Selection for Light‐Emitting Electrochemical Cells

The in situ formation of a light‐emitting p–n or p–i–n junction in light‐emitting electrochemical cells (LECs) necessitates mixed ionic–electronic conductors in the active layer. This unique characteristic requires electronic, luminescent, and ionic ingredients that work synergistically in the LECs. The material requirements that lead to promising electroluminescent properties are discussed and the important components reported so far are surveyed. Particular attention is paid to the working mechanisms behind junction formation and stabilization to create efficient and stable electroluminescence in conjugated‐polymer‐based LECs. Keeping these fundamentals in mind explains how LEC devices have evolved from classic conjugated polymer blends into highly stable crosslinked, hybrid composite, and stretchable device architectures. To conclude, a future development strategy is proposed based on a dual approach: develop new materials specifically for LEC devices and explore novel ways to efficiently process and stabilize the p–i–n junction, which will drive improvements in both LEC external quantum efficiency and operating lifetime toward truly low‐cost solid‐state lighting applications.     

Shape optimization of shallow domes subjected to external pressure

Shallow domes subjected to external pressure are extensively used in missile structures. The critical failure mode for these domes is buckling due to external pressure. Different closed form solutions are available to evaluate buckling pressure of dome shapes like ellipsoid and torisphere. The torisiphere dome is the optimum dome shape among conventional domes. Shape optimization is carried out to find the optimal dome shape among shallow domes subjected to external pressure. Dome geometry is generalized by cubic bezier polynomials. For carrying out shape optimization, a low fidelity model is preferred which can predict the critical buckling pressure of a general dome shape. Towards this a unified model is proposed which meets the above requirement. Using this unified model, shape optimization of dome for minimization of mass is carried out subjected to buckling constraint. The study yielded a dome shape different from conventional dome shapes with a mass saving of 6% over torispherical dome while meeting the buckling constraint. The results of unified model are also validated with high fidelity Finite Element Analysis.

     

Interpenetrating photopolymers for intraocular lens application

Interpenetrating photopolymer network materials suitable for intraocular lens application are presented. A rapidly curable, transparent, hydrophobic material with appropriate optical and thermomechanical properties has been prepared from Benzyl acrylate and Benzyl methacrylate. To improve its biocompatibility and optimize surface—cell interactions, this material was modified with respect to its hydrophobicity. Materials which are more hydrophobic, and more hydrophilic, than the base resin were prepared by copolymerization with either a fluoroacrylate or a PEG acrylate respectively. All materials were characterized for their optical and thermomechanical properties. Their in‐vitro cytotoxicity and interaction with mouse fibroblast cells were also studied. It was shown that all materials of the study were biocompatible and more hydrophilic materials resisted cell attachment and may be more suitable for IOL application than their more hydrophobic counter parts of the study. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44496.