Implicit-explicit time stepping with spatial discontinuous finite elements

In this paper a combination of discontinuous, piecewise linear, finite elements with implicit-explicit time stepping is considered for convection-reaction equations. Combined with low order quadrature rules, this leads to convenient schemes. We shall consider the effect of such low order quadrature rules on accuracy and stability for one-dimensional problems

Effects of photon reabsorption phenomena in confocal micro-photoluminescence measurements in crystalline silicon

Confocal micro-photoluminescence (PL) spectroscopy has become a powerful characterization technique for studying novel photovoltaic (PV) materials and structures at the micrometer level. In this work, we present a comprehensive study about the effects and implications of photon reabsorption phenomena on confocal micro-PL measurements in crystalline silicon (c-Si), the workhorse material of the PV industry. First, supported by theoretical calculations, we show that the level of reabsorption is intrinsically linked to the selected experimental parameters, i.e., focusing lens, pinhole aperture, and excitation wavelength, as they define the spatial extension of the confocal detection volume, and therefore, the effective photon traveling distance before collection. Second, we also show that certain sample properties such as the reflectance and/or the surface recombination velocity can also have a relevant impact on reabsorption. Due to the direct relationship between the reabsorption level and the spectral line shape of the resulting PL emission signal, reabsorption phenomena play a paramount role in certain types of micro-PL measurements. This is demonstrated by means of two practical and current examples studied using confocal PL, namely, the estimation of doping densities in c-Si and the study of back-surface and/or back-contacted Si devices such as interdigitated back contact solar cells, where reabsorption processes should be taken into account for the proper interpretation and quantification of the obtained PL data.Peer ReviewedPostprint (published version

Winner loses all: The 2015 French regional elections

The French regional elections of 2015 presented two contrasting images of France: in the first round, a political landscape divided into three major blocs with the far-right Front National (FN) the dominant force; in the second round, a landscape as bipolarized between centre-right and centre-left as at any time under the Fifth Republic and with the FN a distant third. This article explores these two representations of political France and analyses the elections in relation to the wider French political context. It discusses the electoral dynamics that enabled the traditional parties to preserve their duopoly of regional power despite the increasingly intrusive challenge to their hegemony mounted by an ever more electorally potent FN