All-Solution-Processed Thermally and Chemically Stable Copper–Nickel Core–Shell Nanowire-Based Composite Window Electrodes for Perovskite Solar Cells

Organic–inorganic hybrid perovskite solar cells (PSCs) have recently attracted tremendous attention because of their excellent efficiency and the advantage of a low-cost fabrication process. As a transparent electrode for PSCs, the application of copper nanowire (CuNW)-network was limited because of its thermal/chemical instability, despite its advantages in terms of high optical/electrical properties and low-cost production. Here, the copper–nickel core–shell nanowire (Cu@Ni NW)-based composite electrode is proposed as a bottom window electrode for PSCs, without the involvement of a high-cost precious metal and vacuum process. The dense and uniform Ni protective shell for CuNWs is attainable by simple electroless plating, and the resulting Cu@Ni NWs exhibit outstanding chemical stability as well as thermal stability compared with bare CuNWs. When the Ni layer with the optimal thickness is introduced, the Cu@Ni NW electrode shows a high transmittance of 80.5% AVT at 400–800 nm, and a sheet resistance of 49.3 ± 5 Ω sq–1. Using the highly stable Cu@Ni NWs, the composite electrode structure is fabricated with sol–gel-derived Al-doped zinc oxide (AZO) over-layer for better charge collection and additional protection against iodine ions from the perovskite. The PSCs fabricated with AZO/Cu@Ni NW-based composite electrode demonstrate a power conversion efficiency (PCE) of 12.2% and excellent long-term stability maintaining 91% of initial PCE after being stored for 500 h at room temperature. Experimental results demonstrate the potential of highly stable Cu@Ni NW-based electrodes as the cost-effective alternative transparent electrode, which can facilitate the commercialization of PSCs.