Development of an all-metal thick film cost effective metallization system for solar cells. Final report, May 1980-January 1983

Copper pastes were prepared. Properties of these pastes did not reproduce earlier results in rheology and metallurgy. Electrodes made with pastes produced under the previous contract were analyzed and compared with the raw materials. A needle-like structure was observed on the earlier electroded solar cells, and was identified as eutectic copper-silicon by electron probe x ray spectroscopy. The existence of this phase was thought to benefit electrical and metallurgical properties of the contact. Subsequently electrodes made from new material were also shown to contain this phase while simultaneously having poor adhesion. A solar cell experiment including front contact experimentation was done. No electrical information was obtained due to inadequate contact adhesion. Experiments were conducted with variations in paste parameters, firing conditions, including gas ambients, furnace furniture, silicon surface and others. Semiconductor and solar cell research activities in Munich were visited and activities of mutual interest were discussed. A liquid medium, intended to provide transport during the carbon fluoride decomposition was incorporated in the paste with promising results, resulting in better adhesion and surviving preliminary environmental tests. 2 x 2 cm solar cells made with fluorocarbon activated copper electrodes and gave 7% AMI efficiency (without AR coating).