Using rigorous diffraction theory we investigate the scattering properties of various random textures currently used for photon management in thin-film solar cells. We relate the haze and the angularly resolved scattering function of these cells to the enhancement of light absorption. A simple criterion is derived that provides an explanation why certain textures operate more beneficially than others. Using this criterion we propose a generic surface profile that outperforms the available substrates. This work facilitates the understanding of the effect of randomly textured surfaces and provides guidelines towards their optimization.

By means of a rigorous diffraction theory, we investigate the possibility to enhance the absorption in solar cells by employing localized plasmon polaritons excited in metallic nanowires. The solar cells are assumed to be made of amorphous silicon. We identify two reasons for increased absorption; namely, the giant near-field enhancement and the enhanced scattering cross section upon exciting localized plasmon polaritons. It will be shown that by a careful and rational adjustment of the system parameters an enhancement in the number of absorbed photons from the solar spectrum up to a factor of 1.6 is feasible.

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Directional and energy selective optical surface structures attached to solar cells may result in both, enhancement or deterioration of photovoltaic performance of a solar cell. On the one hand, restricting the cell acceptance to the small incidence angle of direct and circumsolar irradiation enhances the maximum path length of the light in a solar cell with Lambertian surfaces even above the Yablonovitch limit (ultra-light-trapping). On the other hand, restrictions to small acceptance angles imply losses of diffuse sunlight, even for perfectly tracked cells. Using temporally resolved solar irradiation spectra, we simulate the enhancement and loss in the annual energy yield of silicon solar cells of various thicknesses. We assume an idealized angular and energy selective filter on top of the Lambertian surface of the absorber and compare the results to a Lambertian surface only. We find a maximum annual gain in the energy density of 32.5% for 1 mu m, and of similar to 10% for 10 mu m and 100 mu m thick perfectly tracked crystalline silicon solar cells. The simulation implies various tracking modes and two different locations. Finally, we introduce two possible realizations of such a filter; a Ru-gate stack and inverted opals. In experimental measurements, we could verify the absorptance enhancement by such a structure applied on top of a thin silicon wafer

We describe some fundamental properties of localized plasmon polaritons in metallic nanoparticles, and discuss their use for enhancing solar cells efficiency by photon management. Two scenarios are detailed. The first is an example of spectral photon management utilizing localized plasmon polaritons to increase the up‐conversion efficiency of ions embedded in a glass matrix comprising metallic nanoparticles. The second example details quantitatively how the strong field enhancement and the large scattering cross‐section of plasmons at the resonance wavelength can be employed directly to enhance light absorption in thin‐film solar cells. Preliminary experimental results on tailoring appropriate materials are also shown. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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We study numerically in detail optical effects occurring during the interaction of light with dielectric gratings and explain how they can be exploited to enhance light absorption in thin‐film solar cells. We analyze in depth two scenarios with practical relevance where dielectric gratings are incorporated. The first is an one‐dimensional, binary grating, which can be manufactured lithographically. The second is a two‐dimensional grating of dielectric spheres that can be fabricated employing self organization processes on pre‐textured substrates. From a universally valid point of view, we finally outline strategies to optimize the geometry of textured surfaces permitting for a maximization of absorption in a solar cell. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper analyses the e¤ects of downward nominal and real wage rigidities on the transmission of technology shocks in a monetary union under di¤erent monetary policy regimes, including optimal policy. Downward rigid wages imply higher adjustment costs for wage cuts but lower costs for wage increases compared to a symmetric situation. In the presence of downward nominal rigidity aggregate volatility leads to a strictly positive in ‡ation rate. Monetary policy is therefore more responsive following a negative productivity shock compared to a positive one. These e¤ects are stronger the more ‡exible prices are, but are absent in the case of real wage rigidity (indexation). Following a union-wide shock, in which regions di¤er in the type of rigidity, terms of trade always improve over the short-run for the country with real rigidity independently of the direction of the shock. Following asymmetric shocks, relative price adjustments dominate over wage asymmetry leaving responses nearly unaltered to symmetric wage adjustments. We …nd a small role for monetary policy even in the case of purely asymmetric shocks due to curvatures in the prodution and the utility fucntion. Finally, compared to optimal monetary policy, an in ‡ation targetter generates large in ‡ation di¤erentials and terms of trade between countries with the adjustment burden mostly on the nominal rigid country. Commonly used Taylor rules are not aggressive enough during the initial phase of adjustment compared to the optimal policy. JEL classi…cation: E31; E52;C61.