In Situ Formation of NiO_x 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 (VOC) and obtaining an excellent PCE of 13.6%, along with improved stability. This work provides a simple strategy to mitigate the VOC loss for efficient and stable inorganic perovskite devices.