Flexible Cu(In,Ga)Se₂ Based Solar Cells Using Molybdenum Foils as Substrate

Recently, there has been increased interest in the use of flexible substrates for the fabrication of Cu(In,Ga)Se₂ solar cells due to their light weight and easy application. This work focuses on the use of 150 μm thick Mo foils as substrates which has not received much attention compared to other metals such as Ti and Stainless Steel although the coefficient of expansion of Mo better matches that of CIGS. Interestingly, Mo foil can be used as both the substrate and back contact which reduces the manufacturing steps of this type of solar cell. The CIGS absorbers herein were realized by a 3-stage coevaporation process. This work studies the impact of temperature, Na incorporation and the optimization of the Ga gradient on the cell performance using different characterization techniques such as XRD, GD-OES, and IV measurements. Efficiencies up to 14%, with V_oc= 0.60 V, J_sc= 34.1 mA cm⁻² and FF = 70.4% have been obtained.