Silver-carbon-nanotube metal matrix composites for metal contacts on space photovoltaic cells

In this work, multiwalled carbon nanotubes are being investigated for mechanical reinforcement of metal contacts on inverted metamorphic multijunction solar cells. We have focused on a silver-carbon-nanotube layer-by-layer microstructure for our initial studies. The silver layer is electrodeposited, and the carbon nanotube layer is deposited by electrodeposition and nanospreading. To increase adhesion strength to metal and achieve efficient metal-nanotube stress transfer, carbon nanotubes are chemically functionalized with carboxylic or amine groups prior to deposition. The metal-carbon-nanotube composites are currently being characterized mechanically and electrically through nanoindentation and strain failure tests. The initial strain failure tests show that conductivity is maintained with 42-μm-wide microcracks in the composite layer, where the carbon nanotubes bridge the gap.