Double inorganic hole extraction layer of Cs: NiO _x / CuInS ₂ for efficiency and stability enhancement of perovskite solar cells

In this work, we construct a double inorganic hole extraction layer (HEL) of Cs:NiOx/CuInS2 by inserting a thin film of Cs:NiOx between the perovskite (FAPbI3)1-x (MAPbBr3)x and CuInS2 layers and fabricate n-i-p type perovskite solar cells (PSCs) using Cs:NiOx/CuInS2 as HEL. The efficiency of the PSCs with Cs:NiOx/CuInS2 reaches 18.04% from 16.13% for the devices with single HEL of CuInS2, which is close to the highest efficiency (19.24%) of the devices with double inorganic HEL reported. In addition, the operational stability of the devices with Cs:NiOx/CuInS2 is enhanced. The solar cells based on double HEL of Cs:NiOx/CuInS2 maintains 95% of the original PCE after keeping 32 days in ambient air, while the devices based on single HEL of CuInS2 keeps only 84% of the original PCE. In addition, the thermal stability of the PSCs with Cs:NiOx/CuInS2 is also enhanced compared with the devices based on CuInS2. The results demonstrate that the application of double HEL of Cs:NiOx/CuInS2 can enhance the performance and stability of PSCs simultaneously.