Double Inorganic Hole Extraction Layer of Cs:NiO _x/CuInS ₂ for Perovskite Solar Cells with Enhanced Efficiency and Stability

In this work, we constructed a double inorganic hole extraction layer (HEL) of Cs:NiOx/CuInS2 by inserting a thin film of Cs:NiOx between the perovskite and CuInS2 layers, and fabricated n-i-p type perovskite solar cells (PSCs) using it as a HEL. The efficiency of the PSCs with the double HEL of Cs:NiOx/CuInS2 has reached 18.04%, which is higher than that of the device with single HEL of CuInS2 (16.13%). Moreover, the operational stability of the PSCs based on Cs:NiOx/CuInS2 was enhanced. The solar cells based on double HEL of Cs:NiOx/CuInS2 maintains 95% of the initial PCE after keeping in the ambient air for 32 days, while the devices based on the single HEL of CuInS2 keeps only 84% of the initial PCE under the same conditions. In addition, the thermal stability of the PSCs with Cs:NiOx/CuInS2 was 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 efficiency and stability of the perovskite solar cells simultaneously.