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

All-inorganic cesium lead bromide (CsPbBr3) 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 (Voc) in vacuum-deposited CsPbBr3 PSCs. Incorporating a thin layer of CdS between the electron transport layer (ETL) and the inorganic perovskite absorber enhances the Voc 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.