The preparation of antioxidative copper pastes applicable to HIT solar cells metallization

Screen printing of silver pastes remains as the dominant front-side metallization process for solar cells due to its simplicity, low cost and high throughput. However, the cost of silver is too high among the conductive metallic materials. Copper paste is the most promising alternative to silver paste in the future, because the cost of copper nanoparticles is about 1/20 of that of silver nanoparticles. In this study we show the formulation of copper pastes and discuss the correlation between the electrical characteristics of antioxidative copper pastes and the thermal treatment temperatures in an inert nitrogen atmosphere. The copper pastes were deposited on ITO (indium tin oxide) substrates to form the patterns by screen-printing, subsequently annealed at different temperatures in nitrogen atmosphere for 5 minutes. A resistivity of about 5×10
^-5
Ω·cm was achieved when annealed at 250 °C. In addition, these highly conductive copper patterns can be placed in an atmospheric environment for more than six months without the oxidation phenomenon, which were verified by X-ray diffraction (XRD).