In Situ Formation of NiOx Interlayer for Efficient n-i-p Inorganic Perovskite Solar Cells

Inorganic metal halide perovskites with intrinsically good thermal stability are potential candidates for stable perovskite solar cells (PSCs). However, band misalignment between perovskite absorber and hole-transport material (HTM) restricts the maximum attainable photovoltage and power conversion efficiency. In addition, widely used HTM 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro) in the fabrication of highly efficient inorganic PSCs causes stability issue. Here, we report a facial way to deposit an in situ formed NiOx interlayer at low temperature between perovskite and Spiro in inorganic PSCs with an n-i-p configuration. Our results suggest that devices with the NiOx interlayer have better energy alignment and facilitate hole extraction and transfer more efficiently than those without NiOx. This leads to a 100 mV improvement in the open-circuit voltage (V-OC) and obtaining an excellent PCE of 13.6%, along with improved stability. This work provides a simple strategy to mitigate the V-OC loss for efficient and stable inorganic perovskite devices.