Evolution of the optical response of sputtered CdS:O as a function of temperature

The linear absorption spectrum of an oxygenated CdS (CdS:O) thin film was measured as a function of annealing temperature. Subtle changes in the absorption spectrum were observed for short annealing times at temperatures up to 275 °C. Much more significant changes were observed as the temperature was increase from 275 °C to 325°C. Interestingly, at some point, increasing the temperature does not result in a change in the spectrum, indicating complete conversion into CdS. This evolution is also observed when the CdS:O film is capped with a thin film of CdTe. This suggests that an unreacted CdS:O layer is not likely to survive post deposition processing in CdTe solar cells.