Hydrogen plasma treatment of ZnO-coated TCO films

Hydrogen plasma treatment of textured SnO₂:F TCO (transparent conductive oxide) films coated with ZnO layer of 100 Å in thickness was investigated for high efficiency a-Si solar cells. It was found that a ZnO over-layered structure was effective in improving the hydrogen plasma durability. Furthermore, it was shown that the resistivity of over-layered TCO films decreased dramatically after the hydrogen plasma treatment at a temperature of 300°C without any change in optical transmission. The decrease in resistivity was due to the sufficient increase in Hall mobility, which was caused by the elimination of chemical reduction. After the hydrogen plasma treatment under the optimized condition, the highest Hall mobility of 70 cm² /V·sec, sheet resistance below 5 Ω/sq,. and optical transmission above 85% were attained