Horst Witzke

Optically enhanced amorphous silicon solar cells

We describe the first application of optical enhancement to thin‐film (∼0.75 μm thick) amorphous silicon solar cells and define cell geometries which maximize enhancement effects. We observed that due to the improved infrared absorption the external AM1 short circuit current increases by 3.0 mA/cm2 in cells constructed in accordance with the principles of optical enhancement.

Clusters, colloids and catalysis

Abstract Metal cluster molecules containing easily displaceable ligands have been successfully exploited in organometallic cluster synthesis and to a lesser extent in homogeneous catalysis. We have extended this concept to elemental metal clusters in a fluid medium, by stabilizing colloidal transition metal particles in non-polar hydrocarbon solutions using polymers as tenuous ligands to prevent aggregation of the metal. The colloids were prepared by condensation of the metal vapor into a cold solution of the stabilizing polymer. In the absence of polymer, the metal atoms agglomerate into

Realization of a thin film solar cell with a detached reflector

100 μm aggregates of microcrystalline metal, containing crystallites of the order of 20–50 A in diameter. In the presence of polymer, agglomeration of the metal proceeds only to the 20–50 A stage, at which point the polymer sterically stabilizes the metal cluster and prevents further aggregation. The colloidal solutions thus obtained exhibit considerable thermal stability. The homogeneous catalytic properties of these solutions have been investigated in the hydrogenation of acenaphthylene. Colloidal metals prepared in this way also serve as sources of heterogeneous metal catalysts; copper-nickel colloids have been used in this way to probe the particle size dependency of filamentous carbon formation from ethane.