THE ROLE OF OXYGEN IN CUINSE2 THIN-FILMS AND CDS/CUINSE2 DEVICES

The solar cell device CdS/CuInSe//2 has been shown to require a post-treatment in air at about 200 degree C to reach its state-of-the-art efficiency of close to 11%. We have shown that treating the device in a solution of chemical oxidants has the same effect as the annealing in air. The results of oxidation can be reversed by treating the device in a solution of a reducing agent (hydrazine). Several experimental techniques were employed to show that the oxidation process, whether it is chemical or air annealing serves to introduce oxygen into the CuInSe//2 whereas the reduction process serves to remove it. The acceptance of oxygen depends on the stoichiometry of CuInSe//2, and in turn affects the electrical properties. It is this interdependence between stoichiometry and the incorporation of oxygen which determines the extent of improvement in the CdS/CuInSe//2 performance. We have also shown that the oxygen in the CuInSe//2 can be dislodged from the CuInSe//2 material upon exposure to an electron beam.