A Dry Heat-Induced Effect of Using Silver in CIGS Gridlines

The ease with which screen-printed silver is deposited and its high conductivity make it an appealing choice for gridline material on CIGS-based photovoltaic devices. However, present results suggest silver diffusion into the device can cause severe reductions in efficiency after as little as 200 h at 85 °C. Dramatic reductions in fill factor, characterized by unusual inflections in the power quadrant of current-voltage curves, are observed for devices with silver gridlines but not for those with nickel or aluminum gridlines. The shape of the current-voltage curves demonstrate that the degradation mode is not simply due to changes in resistance but is consistent with the creation of a secondary barrier near the device junction.