NiN-Passivated NiO Hole-Transport Layer Improves Halide Perovskite-Based Solar Cell

The interfaces between inorganic selective contacts and halide perovskites (HaPs) are possibly the greatest challenge for making stable and reproducible solar cells with these materials. NiO_x, an attractive hole-transport layer as it fits the electronic structure of HaPs, is highly stable and can be produced at a low cost. Furthermore, NiO_xcan be fabricated via scalable and controlled physical deposition methods such as RF sputtering to facilitate the quest for scalable, solvent-free, vacuum-deposited HaP-based solar cells (PSCs). However, the interface between NiO_xand HaPs is still not well-controlled, which leads at times to a lack of stability and V_oclosses. Here, we use RF sputtering to fabricate NiO_xand then cover it with a Ni_yN layer without breaking vacuum. The Ni_yN layer protects NiO_xdoubly during PSC production. Firstly, the Ni_yN layer protects NiO_xfrom Ni³⁺species being reduced to Ni²⁺by Ar plasma, thus maintaining NiO_xconductivity. Secondly, it passivates the interface between NiO_xand the HaPs, retaining PSC stability over time. This double effect improves PSC efficiency from an average of 16.5% with a 17.4% record cell to a 19% average with a 19.8% record cell and increases the device stability.