Selecting CdS:F or CdS:O for window layer application in CdTe-based solar cells

In this work CdS:F and CdS:O thin films were studied. Films were prepared by the RF-sputtering technique in an atmosphere containing Ar mixed with CHF₃ or O₂ reactive gases. XPS measurements showed that CdS:F films are composed by CdS and CdF₂ while CdS:O comprises the CdS, CdSO₄, CdSO₃ and CdO₂ compounds. Modulation of optical properties was achieved by changing the reactive gas concentration during deposition. According to the transmittance, bandgap and refractive index values, it was concluded that CdS:O thin films are more suitable for window layer application.