It is known that carriers photogenerated in the polycrystalline CdS layer of a CdS/CdTe cell are not collected. Thus, the short-circuit current (JSC) of CdS/CdTe devices should be improved if the bandgap of CdS is increased to permit better blue response. Wu, et al, showed that alloying of CdS with oxygen can increase the absorption edge of the layer. We report here on studies of this ‘oxygenated’ CdS and its use in sputtered cells. We find that at a deposition temperature of 250°C the addition of O2 to the sputter gas results in a red shift of the absorption edge (from 2.35 eV to 1.94 eV), but that room temperature deposition gives a blue shift (from 2.36 eV to 3.28 eV). The Raman spectra of the room temperature deposited films show a considerable broadening of LO phonon peaks suggesting a micro- to nano- to amorphous transition as the O2 fraction increases. XRD measurements of these films confirm the formation of an amorphous structure at high O2 fractions. The quantum efficiency measurements of CdS/CdTe device with room temperature deposited oxy-CdS show an improvement in blue response and hence increased JSC, but are accompanied by poorer junction quality so that the overall efficiency is not increased.