Crack-Tolerant Metal Composites as Photovoltaic Gridlines

Multiwalled carbon nanotubes are used to electromechanically reinforce metal gridlines and busbars on commercial triple-junction solar cells. For the reinforcement, we create a layer-by-layer microstructure which consists of electroplated silver, spray-coated carbon nanotubes, and another layer of electroplated silver. The top silver layer is intercalated through the network of carbon nanotubes, connecting with the bottom silver layer. This metal matrix composite integration leads to beginning-of-life cell performance identical to the control cells with conventional metallization. Fill factor and efficiency remain the same. When the cells are intentionally cracked, the composite-reinforced cells maintain superior performance compared with the control cells. The key difference is that short-circuit current density of composite-reinforced cells remains essentially unaffected, whereas a reduction >50% is observed for the control cells. The metal matrix composites show strong potential to improve the reliability and service time of space photovoltaics against stress-induced fractures.