Phosphine Oxide Derivative as a Passivating Agent to Enhance the Performance of Perovskite Solar Cells

Defects of metal-halide perovskites detrimentally influence the optoelectronic properties of the thin film and, ultimately, the photovoltaic performance of perovskite solar cells (PSCs). Especially, defect-mediated nonradiative recombination that occurs at the perovskite interface significantly limits the power conversion efficiency (PCE) of PSCs. In this regard, interfacial engineering or surface treatment of perovskites has become a viable strategy for reducing the density of surface defects, thereby improving the PCE of PSCs. Here, an organic molecule, tris(5-((tetrahydro-2H-pyran-2-yl)oxy)pentyl)phosphine oxide (THPPO), is synthesized and introduced as a defect passivation agent in PSCs. The P=O terminal group of THPPO, a Lewis base, can passivate perovskite surface defects such as undercoordinated Pb2+. Consequently, improvement of PCEs from 19.87 to 20.70% and from 5.84 to 13.31% are achieved in n−i−p PSCs and hole-transporting layer (HTL)-free PSCs, respectively

Volatility spillovers and cross-hedging between gold, oil and equities: Evidence from the Gulf Cooperation Council countries

The paper examines the return and volatility spillovers between crude oil, gold and equities, and investigates the usefulness of the two commodities in hedging equity portfolios. Using daily data from January 20043 to May 2016 for the Gulf Cooperation Council countries, a DCC-GARCH model is used to estimate dynamic correlations and hedge ratios. We find significant spillovers from oil to equities, highlighting the heavy dependence of the local economies on oil. Moreover, the spillovers of gold on the stock markets are insignificant, suggesting that gold price fluctuations do not necessarily influence equity investment decisions. In the opposite direction, we find that equities do not exert significant influence on the two commodities, which we attribute to the relatively small capitalisation of the exchanges. Our results reveal low dynamic correlations and hedge ratios, with a few spikes during crises, indicating that oil and gold are cheap hedges for stocks, albeit not good ones, while they could be considered as weak safe havens, but at a considerable cost

The future of Cybersecurity in Italy: Strategic focus area

This volume has been created as a continuation of the previous one, with the aim of outlining a set of focus areas and actions that the Italian Nation research community considers essential. The book touches many aspects of cyber security, ranging from the definition of the infrastructure and controls needed to organize cyberdefence to the actions and technologies to be developed to be better protected, from the identification of the main technologies to be defended to the proposal of a set of horizontal actions for training, awareness raising, and risk management

Reduction of Secondary Electron Yied (SEY) Figures on Smooth Metallic Surfaces by Means of Magnetic Roughness

High secondary electron yield of metallic surfaces used in accelerator and also in space applications is of general concern. In addition to several well-known coating preparation techniques and microscopic or macroscopic mechanical roughness (grooves) which may significantly increase microwave losses the concept of magnetic surface roughness has been proposed recently to lower the effective secondary electron yield (SEY). In this concept a smooth and very good conducting surface with low microwave losses is maintained, but underneath this surface a large number of tiny permanent magnets are located to build a rough magnetic equipotential structure. In this paper we present and discuss measurement of the SEY and the improvement in terms of SEY for different parameter ranges