A comparative study of the impact of Mo and stainless steel substrates on the properties of Cu(In,Ga)Se₂ based solar cells

Metallic substrates are well suited for the deposition conditions of Cu(In_x,Ga_1-x)Se₂ (CIGS) solar cells due to their high temperature tolerance. In this work, Molybdenum (Mo) and stainless steel substrates were used in CIGS cell fabrication. Mo foil can be utilized as both the substrate and back contact in the cells. On the other hand, stainless steel despite requiring an impurity barrier layer and back contact deposition, remains economically more interesting. The CIGS absorbers were deposited on the metallic substrates in a 3-stage process at 480 °C. Due to the low deposition temperature, no impurity barrier layer was applied on the stainless steel substrates. For the same deposition conditions, the absorbers on the Mo substrates had a lower [Ga]/[Ga] + [In] ratio (GGI) of 0,24 as compared to 0,28 on the stainless steel substrates. Although the same absorber deposition process was applied to both substrate types, the highest efficiency of 14,0% was recorded on the Mo substrates.