CdS-Based Interface Engineering for 1.7 V Voltage Vacuum-Deposited Inorganic Perovskite Solar Cells

All-inorganic cesium lead bromide (CsPbBr 3 ) perovskite solar cells (PSCs) have gained significant attention due to their superior stability compared to that of organic–inorganic hybrid devices. In this study, we employ a vacuum-deposited cadmium sulfide (CdS) interfacial layer to address the challenge of achieving a high open-circuit voltage ( V oc ) in vacuum-deposited CsPbBr 3 PSCs. Incorporating a thin layer of CdS between the electron transport layer (ETL) and the inorganic perovskite absorber enhances the V oc to 1.7 V, along with the power conversion efficiency (PCE) increase from 7.8% to 8.4%. Moreover, adding this interfacial layer improves the charge extraction by potentially reducing grain boundary recombination centers via enlarging perovskite grain sizes. Our results show the average perovskite grain size increases from 4 μm to 6 μm on CdS incorporated samples compared to the control. This work reveals the potential of using CdS as a passivation layer to improve charge extraction characteristics by minimizing bimolecular recombinations.