Fig. 4. Variation of performance parameters, i.e., V_OC (V), J_SC (mA cm⁻²), FF (%), and PCE (%) of Cs₂BiAgI₆ absorber layer-based PSCs device for different HTLs with Au as back metal contact and ETLs of (a) PCBM, (b) TiO₂, (c) ZnO, (d) SnO₂, (e) IGZO, and (f) WS₂.