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

Abstract

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_<i>x</i>, 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_<i>x</i> 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 NiO_<i>x</i> and HaPs is still not well-controlled, which leads at times to a lack of stability and <i>V</i>_oc losses. Here, we use RF sputtering to fabricate NiO_<i>x</i> and then cover it with a Ni_<i>y</i>N layer without breaking vacuum. The Ni_<i>y</i>N layer protects NiO_<i>x</i> doubly during PSC production. Firstly, the Ni_<i>y</i>N layer protects NiO_<i>x</i> from Ni³⁺ species being reduced to Ni²⁺ by Ar plasma, thus maintaining NiO_<i>x</i> conductivity. Secondly, it passivates the interface between NiO_<i>x</i> 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.