Quinacridone derivative as a thickness-insensitive cathode interlayer for efficient and stable inverted perovskite solar cells

Cathode interlayer (CIL) has crucial effects on the efficiency and stability of inverted perovskite solar cells (IPVSCs). However, the thickness of used CILs was limited below 10 nm due to their low conductivity, posing a significant challenge for the large size printing of IPVSCs. Herein, we introduced a quinacridone derivative (DCNQA-PyBr) as a thickness-insensitive CIL for IPVSCs and investigated its working mechanism in the devices. Power conversion efficiency (PCE) just decreased from 23.07 % to 18.82 % as DCNQA-PyBr thickness from 18 nm to 103 nm because charge carrier mobility, and charge extraction and recombination did not greatly change with increasing CIL thickness. However, the PCE of control devices with BCP as the CIL drastically dropped from 22.16 % to 7.94 % as CIL thickness from 6 nm to 38 nm due to serious deterioration in terms of charge carrier mobility, and charge extraction and recombination with increasing CIL thickness. In addition, the devices with DCNQA-PyBr exhibited excellent thermal stability as its thickness from 18 to 103 nm because it could form high-quality films at various thickness and even keep intact after annealing. Therefore, DCNQA-PyBr is a promising thickness-insensitive CIL candidate in the roll-to-roll production of IPVSCs modules.