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The lifetime-limiting failure mechanisms of CuInGaSSe (CIGSS) solar devices made by Shell Solar Industries (SSI) were investigated. In our study, SSI minimodules were exposed to dry-heat 85°C, damp-heat 85°C/85% RH and aerobic and anaerobic room temperature and 85°C water baths. After 200 hours exposure to moisture-containing environments, the average device performance decreased by more than 30% that of the initial state. The observed degradation was primarily due to losses in short circuit current density (J sc ) and fill factor (FF). The as-received device layers were relatively dense and free of voids. Interestingly, unreacted Cu-Ga particulates were found at the Mo-CIGSS interface. Corresponding with these particulates, CIS-rich defects were found within the bulk CIGSS material. Post-environmental weathering, Kirkendall-like voids were found in the Al:ZnO and CdS layers of these devices. Additionally, ToF-SIMS analysis revealed the Cu-Ga/CIS defects were enriched in Na and O. Our results indicate that in addition to moisture-induced failure of the window layers, the unreacted Cu-Ga particulates and the corresponding CIS-defects may facilitate moisture and/or oxygen-induced failure of these devices.

Multilayer oxide thin film stacks of aluminum doped zinc oxide (AZO) and tin doped indium oxide (ITO) have been sequentially deposited on soda lime glass substrates by RF sputtering of AZO and ITO ceramic targets at a substrate temperature of 150 °C. The ratio of the AZO thickness to the ITO thickness is varied while keeping the total thickness of the stack constant. The electrical and optical properties of the multilayer stacks have been investigated as a function of this ratio and the number of interfaces. The experimental results are compared and their impact on device performance is demonstrated by simulations with validated AMPS-1D models. XRD and microscopy measurements have been carried out to understand the microstructure of the multilayer system and to establish its correlation with the opto- electric properties. The results have been evaluated for use of these multilayer TCO stacks as potential window layers for the photovoltaic solar cell applications.