Unlocking High Efficiency in (Ag,Cu)(In,Ga)Se₂ Solar Cells: A Parametric Study on Silver Alloying

The partial substitution of copper (Cu) with silver (Ag) in Cu(In,Ga)Se₂ (CIGS) thin-film solar cells represents a transformative approach to improving absorber layer properties and boosting device efficiency. This study will examine and discuss the effect of Ag alloying (0 < Ag/(Ag+Cu) < 0.3) via thermal evaporation, combined with rubidium fluoride (RbF) post-deposition treatment, on samples with bandgaps ranging from 1.1 to 1.5 eV. The approach significantly affects gallium grading, grain size, open-circuit voltage (Voc), and fill factor (FF), achieving a power conversion efficiency (PCE) up to 20.4% for a ACIGS absorber with a 1.2 eV bandgap.