Oxygen incorporation into CdS/CdTe thin film solar cells

CdS/CdTe thin films with 2.1 µm thickness were grown using R.F. magnetron sputtering in two different mixtures of Ar and O₂. The substrate was a commercially available Pilkington glass with TCO deposited. The concentration of O₂was selected to be 0, 1 and 5%. The crystallographic, morphological, optical and electrical properties of the as-deposited samples were compared with the ones treated with CdCl₂and subsequently annealed at high temperature. The films morphology and crystallinity were studied by X-ray diffraction and scanning electron microscopy. X-ray diffraction shows a transition of zinc blend cubic phase to hexagonal as the oxygen content increases from 0 to 5%. The measurements show the larger band gap and grain sizes for the films with higher oxygen content. The band gap and transmission rate of the O₂-free and oxygenated devices is different and the grains size is greatly affected by the oxygen content.