Stability Analysis of Cr-MIS Solar Cells

The 50 Å Cu / 30 Å Cr / 20 Å SiOx / Si solar cell structure has been analyzed by Auger, ESCA and ellipsometer measurements. An oxidation-reduction failure mechanism has been proposed for shelf-life degradation, and experimental evidence for such behavior is presented. The effect of this degradation is a decrease in the oxide thickness at the interface bringing about a photovoltaic performance degradation. The performance degradation involves a typical change in V oc, from about 0.55 V to 0.52 V with little or no change in J sc or fill factor. The performance of all Cr-MIS devices then stabilizes when a thermodynamic equilibrium is attained. The light-effect degradation is more complex and the rearrangement of bonding in the interface oxide and at the SiOx / Si interface might reduce the rate of degradation. The Cr-MIS solar cell should be designed with an oxide thickness more than the static optimum value to allow for a decrease in oxide thickness to the optimum value.