Improvement of Ohmic Contact Between the Indium Tin Oxide and Copper-Plated Contact of Solar Cells by Using the Cu-Sn Alloy Film.

Copper plating has been considered as a future metallization technique to reduce metal contact area and material cost in silicon heterojunction (SHJ) solar cells. In this paper, a Cu-Sn alloy film is used as a seed layer material on an indium tin oxide (ITO) layer with the goal to enhance contact resistivity between the seed and ITO layer. The contact resistivity between the seed layer and ITO is an important parameter because low contact resistivity is required for the high fill factor of the solar cells. In addition, it was confirmed that tin diffusion to ITO can affect contact resistivity by annealing samples having a Cu-Sn seed layer. Contact resistivity values of the samples were extracted by using transfer length method (TLM). Atomic percentage of tin in the Cu-Sn film was measured by the energy dispersive spectrometer (EDS). Also, tape tests were carried out to simply confirm the adhesion of contacts with the Cu-Sn seed layer.