Unveiling the Effects of Spray and Selenization Process Optimization for Over 13% Efficient CIGSSe Solar Cells through the Aqueous Solution Method

Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells were fabricated by using a spray deposition technique based on the ecofriendly aqueous solution in an ambient air environment that is suitable for a low cost manufacturing process. The effects of spray time and postselenization conditions on the thin film properties and the performance of the CIGSSe solar cells were investigated. It was revealed that a slower temperature ramping process during selenization promotes the formation of the larger and the denser CIGSSe grains with minimal residual oxygen content. The optimized annealing profile significantly reduces defect densities and defect energies, confirmed by thermal admittance spectroscopy (TAS). The water-based method achieved a power conversion efficiency (PCE) exceeding 13% for CIGSSe solar cells, without requiring additional treatment or interface modification layers.