No abstract

The influence of a retro-reflective texture cover on light in-coupling and light-trapping in thin film silicon solar cells is investigated. The texture cover is applied to the front glass of the cell and leads to a reflectance as low as r % 3% by reducing the reflection at the air/glass interface and indirectly also reducing the reflections from the internal interfaces. For weakly absorbed light in the long wavelength range, the texture also enhances the light-trapping in the solar cell. We demonstrate an increase of the short circuit current density of exemplary investigated thin film silicon tandem solar cells by up to 0.95 mA cm À2 and of the conversion efficiency by up to 0.74% (absolute). For a planar microcrystalline solar cell, the enhancement of light-trapping was determined from the reduced reflection in the long wavelength range to be up to 17%, leading to an increase of the external quantum efficiency of up to 12%.

Kohlstedt, Hermann; Fitsilis, M.; Waser, R.; Reese, T.J.; Ducharme, Stephen; and Rije, E., "Low-voltage operation of metalferroelectric-insulator-semiconductor diodes incorporating a ferroelectric polyvinylidene fluoride copolymer Langmuir-Blodgett film" (2006 We report the electrical characteristics of metal-ferroelectric-insulator-semiconductor structures, where the ferroelectric layer is a Langmuir-Blodgett film of a copolymer of 70% vinylidene fluoride and 30% trifluoroethylene. The 36-nm thick copolymer films were deposited on thermally oxidized ͑10 nm SiO 2 ͒ p-type silicon and covered with a gold gate electrode. Polarization-field hysteresis loops indicate polarization switching in the polymer film. The device capacitance shows hysteresis when cycling the applied voltage between ±3 V, exhibiting a zero-bias on/off capacitance ratio of over 3:1 and a symmetric memory window 1 V wide, with little evidence of bias that can arise from traps in the oxide. Model calculations are in good agreement with the data and show that film polarization was not saturated. The capacitance hysteresis vanishes above the ferroelectric-paraelectric transition temperature, showing that it is due to polarization hysteresis. The retention time of both the on and off states was approximately 15 min at room temperature, possibly limited by leakage or by polarization instability in the unsaturated film. These devices provide a basis for nonvolatile data storage devices with fast nondestructive readout.

No abstract

Recently, there is much interest in nanocomposites consisting of metal nanoparticles dispersed in a dielectric matrix due to their novel functional properties offering hosts of new applications. Polymers are particularly attractive as matrix. Consequently, various approaches have been reported to incorporate metal nanoparticles into polymers. The present review is mainly concerned with the preparation of polymer-based nanocomposites by co-and tandem sputtering of metallic and organic components and the resulting functional properties. Different from typical wet chemical approaches, this vapor phase deposition technique allows the preparation of composites which contain alloy clusters of well defined composition. Emphasis is placed on soft-magnetic high frequency materials with cut-off frequencies well above 1 GHz and optical composites with tuned plasmon resonances suitable for ultrathin color filters, Bragg reflectors, and other devices. In addition, antibacterial coatings are addressed.