LAUSR

Cu(In,Ga)Se₂ (CIGS)-based photovoltaic cells were fabricated under varying deposition conditions for the Mo back contact and CIGS absorber layers. Specifically, O₂ concentration and sputtering pressure were varied during the Mo deposition, as well as the final Mo-layer thickness. The maximum deposition temperature was then varied during the subsequent deposition of the CIGS-layer by thermal coevaporation. The JV response curve of the finished devices were recorded and used to calculate the usual solar performance characteristics (efficiency, J_sc, V_oc, fill-factor, R_oc, and R_sc). The effects of the varied fabrication conditions on these characteristics were then investigated, and CIGS-deposition temperature alone was found to have had a significant influence on J_sc. Following this, the entire JV-curve was analyzed using functional data analysis (FDA). The curve shape was revealed to be affected not only by temperature, but by O₂ conc. and Mo sputter pressure as well. The effect of these fabrication parameters was greatest in regions of the curve larger than V_oc. External quantum efficiency measurements on the finished devices were also studied using FDA, indicating a strong influence of temperature in reducing collection across most of the visible spectrum. Mechanisms that aim to explain these observations are proposed. This work details, according to the authors’ best knowledge, the first-ever use of FDA in the analysis of photovoltaic devices.