Force nucléaire

Résumé

La force nucléaire, qui s'exerce entre nucléons, est responsable de la liaison des protons et des neutrons dans les noyaux atomiques. Elle peut être interprétée en termes d'échanges de mésons légers, comme les pions. Même si son existence est démontrée depuis les années 1930, les scientifiques n'ont pas réussi à établir une loi permettant de calculer sa valeur à partir de paramètres connus, contrairement aux lois de Coulomb et de Newton. Elle est parfois appelée force forte résiduelle, pour la distinguer de l'interaction forte que l'on explique à partir de la chromodynamique quantique. Cette formulation a été introduite dans les années 1970 en raison d'un changement de paradigme. Auparavant, la force nucléaire forte désignait la force entre nucléons. Après l'introduction du modèle des quarks, linteraction forte a désigné les forces définies par la chromodynamique quantique, qui interagissent avec les quarks, en raison de leur charge de couleur. Les nucléons n'ayant aucune charge de c

Source officielle

https://fr.wikipedia.org/wiki/Force_nucl%C3%A9aire

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Doping Evolution and Junction Formation in Stacked Cyanine Dye Light-Emitting Electrochemical Cells

Matia Bulloni, Roland Hany, Beat Ruhstaller, Lei Wang

Cyanine dyes are fluorescent organic salts with intrinsic conductivity for ionic and electronic charges. Recently (J. Am. Chem. Soc. 2013, 135, 18008-18011), these features have been exploited in cyanine light-emitting electrochemical cells (LECs). Here, we demonstrate that stacked, constant-voltage driven trimethine cyanine LECs with various counteranions develop a p-i-n junction that is composed of p- and n-doped zones and an intrinsic region where light-emission occurs. We introduce a method that combines spectral photocurrent response measurements with optical modeling and find that at maximum current the intrinsic region is centered at similar to 37% away from the anode. Transient capacitance, photoluminescence and attenuance experiments indicate a device situation with a narrow p-doped region, an undoped region that occupies similar to 72% of the dye layer thickness and an n-doped region with a maximum doping concentration of 0.08 dopant/cyanine molecule. Finally, we observe that during device relaxation the parent cyanines are not reformed. We ascribe this to irreversible reactions between doped cyanine radicals. For sterically conservative cyanine dyes, this suggests that undesired radical decomposition pathways limit the LEC song-term stability in general.

Amer Chemical Soc2016

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Model-based optical and electrical characterization of dye-sensitized solar cells

Guido Rothenberger, Matthias Schmid, Sophie Wenger

We present an experimentally validated coupled optical and electrical model for the dye-sensitized solar cell. The light absorption and subsequent charge generation in the photoactive layer is calculated accurately using coherent and incoherent optics. The charge generation function is then used as a source term in the electron continuity equation of the electrical model. The optical model allows to precisely analyze the reﬂection and absorbance losses in the individual layers. By comparing the calculated and measured quantum efficiency of a test device, one can assess the electron recombination losses at short-circuit conditions. We conclude with an integrated power loss analysis to quantify the contribution of the respective optical and electric loss mechanisms.

2009

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The design and development of dye-sensitized solar cells (DSCs) is currently often realized on an empirical basis. In view of assisting in this optimization process, we present the framework of a model which consists in a coupled optical and electrical model of the DSC. The experimentally validated optical model, based on a ray-tracing algorithm, allows accurate determination of the internal quantum efficiency of devices, an important parameter that is not easily estimated. Coupling the output of the optical model-the dye absorption rate-to an electrical model for charge generation, transport, and first-order (linear) recombination allows extraction of a set of intrinsic parameters from steady-state photocurrent measurements, such as the diffusion length or the dye electron injection efficiency. Importantly, the sources of optical and electric losses in the losses). The model has been validated for two dye systems (Z907 and C101) and the strong effect of the presence of Li+ ions in the electrolyte on intrinsic parameters is confirmed. This optoelectronic model of the DSC is a significant step toward a future systematic model-assisted optimization of DSC devices.

American Chemical Society2011

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