University of Bath

About: University of Bath is a education organization based out in Bath, Bath and North East Somerset, United Kingdom. It is known for research contribution in the topics: Population & Photonic-crystal fiber. The organization has 15830 authors who have published 39608 publications receiving 1358769 citations. The organization is also known as: Bath University.

What is moving in hybrid halide perovskite solar cells

Abstract: Organic-inorganic semiconductors, which adopt the perovskite crystal structure, have perturbed the landscape of contemporary photovoltaics research. In this Account, we discuss the internal motion of methylammonium lead iodide (CH$_3$NH$_3$PbI$_3$) and formamidinium lead iodide ([CH(NH$_2$)$_2$]PbI$_3$), covering: (i) molecular rotation-libration in the cuboctahedral cavity; (ii) drift and diffusion of large electron and hole polarons; (iii) transport of charged ionic defects. These processes give rise to a range of properties that are unconventional for photovoltaic materials, including frequency-dependent permittivity, low electron-hole recombination rates, and current-voltage hysteresis. Multi-scale simulations - drawing from electronic structure, ab initio molecular dynamic and Monte Carlo techniques - have been combined with neutron scattering and ultra-fast vibrational spectroscopy to qualify the nature and timescales of the motions. Recent experimental evidence and theoretical models for simultaneous electron transport and ion transport in these materials has been presented, suggesting they are mixed-mode conductors with similarities to metal oxide perovskites developed for battery and fuel cell applications. We expound on the implications of these effects for the photovoltaic action. The temporal behaviour found in hybrid perovskites introduces a sensitivity in materials characterisation to the time and length scale of the measurement, as well as the history of each sample. It also poses significant challenges for accurate materials and device simulations. Herein, we critically discuss the atomistic origin of the dynamic processes.

"Evidence" in chronic pain--establishing best practice in the reporting of systematic reviews.

Abstract: ‘‘Evidence” in chronic pain – establishing best practice in the reporting of systematic reviews R. Andrew Moore *, Christopher Eccleston , Sheena Derry , Phillip Wiffen , Rae F. Bell , Sebastian Straube , Henry McQuay , for the ACTINPAIN writing group of the IASP Special Interest Group (SIG) on Systematic Reviews in Pain Relief and the Cochrane Pain, Palliative and Supportive Care Systematic Review Group editors

Social Assistance in Oecd Countries

Abstract: This article presents selected results from the first comparative study of social assistance across all 24 countries of the OECD. The scope of social assistance, discussed in the first section, is drawn to include all means-tested benefits in cash and kind, including those which provide benefits to higher income groups. The second section then presents in formation on the main programmes in each country, expenditures and groups of beneficia ries, trends over time, administrative struc tures, and operation of means tests. It concludes by developing a new measure of assistance benefit levels with which to evaluate different countries' systems. The third section distils from the country differences eight pat terns, or 'assistance regimes', varying from the limited, discretionary, decentralized models of Switzerland and Norway to the extensive, national, rights-based programmes of the English-speaking world; and from the relative generosity of Scandinavia and Australia to the low, marginalizing benefits of th...