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. NiOx, 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, NiOx can 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 NiOx and HaPs is still not well-controlled, which leads at times to a lack of stability and Voc losses. Here, we use RF sputtering to fabricate NiOx and then cover it with a NiyN layer without breaking vacuum. The NiyN layer protects NiOx doubly during PSC production. Firstly, the NiyN layer protects NiOx from Ni3+ species being reduced to Ni2+ by Ar plasma, thus maintaining NiOx conductivity. Secondly, it passivates the interface between NiOx and 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.